500 short-answer questions on coal transportation in power plants

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1. Briefly describe the production process of a thermal power plant. Answer: The production process in a thermal power plant can be summarized as follows: The chemical energy of fuel is converted into thermal energy through combustion, which is used to heat water into steam at a certain pressure and temperature. This steam then drives a turbine, converting thermal energy into mechanical energy that causes the rotor to rotate; finally, a generator converts this mechanical energy into electrical energy. 2. What are the main systems, auxiliary systems, and facilities involved in the production process of a thermal power plant? Answer: The main production systems involved in the operation of a thermal power plant are the steam and water system, the fuel system, and the electrical system. In addition, there are various auxiliary systems such as water supply systems, chemical systems, coal conveying systems, and thermal automation systems, as well as corresponding facilities such as workshops, buildings, and structures. 3. What is a coal transport system in a power plant? What equipment is generally included? Answer: The coal transport system in a power plant encompasses the entire production process, from transporting coal directly from the unloading equipment to the raw coal bin in the boiler room, and then transferring the coal to the raw coal hopper via a coal storage area. A coal transportation system generally includes fuel transportation equipment, coal unloading machinery, coal volume measurement devices, coal yard facilities, coal transportation equipment and screening and crushing devices, centrally controlled or programmatically controlled equipment, as well as other auxiliary equipment and auxiliary buildings. 4. What equipment does the coal transportation system in thermal power plants consist of? Answer: The coal transportation system is mainly composed of coal unloading equipment, coal feeding equipment, coal loading equipment, coal blending equipment, coal plant-related equipment, and auxiliary equipment. 5. What are the reasons for oil leakage in reducers? Answer: The reasons for oil leakage in reducers are: (1) Rough machining of the mating surfaces. (2) The reducer housing deforms after long-term operation, resulting in a poor fit at the joint surfaces. (3) Excessive oil in the tank. (4) An excessive sealing gap between the bearing cover and the hole causes oil leakage from the bearing cover. The main reason for oil leakage from the end cover is the blockage of the oil return groove inside the bearing cover; there being a certain gap with the end cover, oil leaks out through this gap. (5) The joint surface of the observation hole is uneven, the paper gasket at the joint surface is damaged, and poor sealing leads to oil leakage at the joint surface. 6. What are the requirements for rolling bearing assembly? Answer: Generally speaking, the degree of fit for bearings should be determined based on the application requirements; a tighter fit is required in situations with high rotational speeds, large loads, and significant vibrations ； Conversely, use a looser fit. The fit between the inner ring of the bearing and the shaft is a transition fit based on the hole system, while the fit between the outer ring of the bearing and the hole is a transition fit based on the shaft system ； When assembling large bearings, a static fit or a transitional fit based on the hole system should be used. 7. What is the significance of the clearance in rolling bearings? Answer: The clearance in rolling bearings includes radial clearance and axial clearance; it refers to the maximum amount of movement of one bearing ring in the radial and axial directions, with the other bearing ring being fixed. For a certain type of bearing, the radial clearance and the axial clearance influence each other, and there is a specific conversion relationship between them. 8. What are the quality requirements for tape bonding? Answer: The quality requirements for tape bonding are as follows: (1) The unevenness in the equal division of various sections of the tape shall not exceed 1 mm. (2) The surface of the cut area must be smooth, with no cracks. (3) When using a wire wheel to remove residual glue, ensure it is cleaned thoroughly. (4) The edge of the tape at the joint should be a straight line, with a straightness of less than 0.3%. (5) The quality of the joint must ensure its usability for over one year, during which no defects such as holes, delamination, or cracked edges should occur. 9. What is the function of a belt coal conveyor? Answer: Its function is to transport the coal from the coal unloading chute to the boiler’s raw coal hopper. 10. Briefly describe the advantages of ring coal crushers. Answer: Ring coal crushers have the following advantages: (1) High crushing capacity, low power consumption, and high efficiency. (2) It has a simple and compact structure, occupies little space, possesses high stiffness, and is lighter in weight compared to hammer and impact types. (3) Ensure that the discharge particle size is below 30 mm and the discharge is uniform. (4) Since the hammer ring can swing freely, when it encounters a harder object, the ring hammer automatically retracts and is reflected into the iron removal chamber by the material shifter. (5) The hammer ring has a low blowing effect, the machine occupies less space, the air volume is low, and there is less coal dust leakage. (6) It has reliable operation, is easy to adjust, convenient for maintenance, requires little upkeep, and has strong adaptability to changes in coal type. (7) Low operating noise. (8) The unit has low vibration. (9) The materials used in the unit are appropriate, ensuring a long service life. 11. Briefly describe the principle of electric actuators. Answer: After the motor starts, it reduces speed through a pair of gears, thereby driving the screw to rotate. The nut that is meshed with the screw moves along the guide rails fixed on the inner wall of the guide sleeve. The push rod is connected to the nut by screws; as the nut moves forward, it pushes the push rod outward. Conversely, when the motor rotates in the reverse direction, the push rod retracts. In this way, after the motor is slowed down by this pair of gears, it drives a screw-nut assembly to convert the motor’s rotational motion into linear motion of the push rod; the forward and reverse rotation of the motor is used to carry out the pushing action. The push rod is equipped with an automatic overload protection system; when the push rod is overloaded or reaches its maximum travel distance, the limit switch automatically shuts off, stopping the push rod and thus providing overload protection to prevent damage to the motor and other components. 12. Briefly describe the components of an impeller coal feeder. Answer: An impeller coal feeder is mainly composed of a main drive mechanism and a crane drive mechanism. The main drive mechanism includes: electric motor, coupling, reducer, bevel gear reducer, impeller, etc ； The vehicle transmission mechanism includes a motor, a reduction gearbox, couplings, a worm gear reduction gearbox, wheels, couplings, a control system, etc. 13. Briefly describe the components of a belt conveyor. Answer: A belt conveyor is mainly composed of the belt (ordinary belt and steel wire rope belt), idlers (including grooved, parallel, cushioned, and automatically adjusting idlers), as well as the frame. It also includes a driving device (in which an electric motor drives the drums through a coupling and a reducer), a tensioning device (which can be of the weight-type or screw-type), deflection drums, braking devices (such as belt brakes, roller brakes, electro-hydraulic brakes, and electromagnetic brakes), and a cleaning device. 14. What causes the coal pusher to make a “whooshing” sound? How should it be dealt with? Answer: The radial clearance of the main bearing is too large. Check the gap; if it exceeds the limit, it should be replaced. 15. Why does vibration occur when the gears of a loading/unloading bridge skip teeth? How to solve it? Answer: The gears are severely worn or damaged. A new gear should be replaced. 16. What are the reasons for the hydraulic system pressure to exceed the specified value? How should it be dealt with? Answer: The reasons for the hydraulic system pressure to exceed the specified value are: (1) The main valve of the relief valve is stuck. (2) Oil holes are blocked. The solution is: shut down the system for maintenance. 17. What are the advantages of gear transmission? Answer: The advantages of gear transmission are its compact structure ； Wide range of applications ； It ensures that the gear ratio remains constant ； High mechanical efficiency ； It operates reliably and has a long service life, with low stress on the shafts and bearings. 18. What are the criteria for selecting bearings? Answer: The main criteria for selecting bearings are the magnitude and direction of the load, as well as the nature of use. 19. What are the components of a hydraulic system? Answer: A hydraulic system consists of a power unit, an actuating unit, a working fluid, and auxiliary components. 20. Into which categories can lubrication be divided? Answer: Lubrication can be divided into three categories: hydrodynamic lubrication, elastohydrodynamic lubrication, and boundary lubrication. 21. What is the function of lubrication? Answer: It reduces frictional losses between moving and stationary parts of mechanical equipment, minimizes wear on the contact surfaces, reduces vibrations, provides sealing, and helps with heat dissipation. 22. What are the main components of the coal transportation system in a thermal power plant? Answer: The coal transportation system in a thermal power plant mainly consists of coal unloading equipment, coal feeding equipment, coal loading equipment, coal blending equipment, coal yard equipment, and auxiliary equipment. 23. The belt deviates when loaded but not when unloaded. What is the cause? How can it be eliminated? Answer: The reason is that the coal dropping point is not in the correct position. Eliminate the issue by adding baffles and adjusting the coal falling point. 24. What are the reasons for abnormal wear of the adhesive surface of the tape? How to solve it? Answer: The reasons are: (1) There are debris between the adhesive plate of the guide groove and the tape. (2) The glue plate of the material guide groove is too hard. The solution is: (1) Stop the machine and remove debris. (2) Replace the rubber sheet. 25. Why do the traveling wheels of the impeller coal feeder severely damage the rails? How to deal with it? Answer: Because: (1) uneven gauge. (2) The traveling wheel is skewed. The solution is: (1) Adjust the gauge. (2) Solve the problem of skewed walking wheels. 26. Describe the cold adhesive bonding process for tapes. Answer: The cold adhesive bonding process for tapes is as follows: (1) First, preheat and dry the damp tapes. (2) Line drawing, cutting and stripping. Then, use a wire grinding wheel to remove the residual glue from the surface of the core layer until the canvas becomes slightly fuzzy, and clean it up. (3) Apply glue. Apply a layer 0.4 mm thick in the first pass, and dry it using an iodine-tungsten lamp. Apply a second coat of glue once the surface is no longer sticky to the touch. Apply a slightly smaller amount of glue on the second application, then dry it; once the surface of the glue is sticky but not too sticky, the pieces can be joined together. (4) When closing the joints, the corresponding steps should be aligned, and then the area should be struck with a hammer from the center outward to expel air and ensure a strong bond between the joints. The hammering force should be even, and this process should be carried out across the entire joint area. (5) Repair the interface edges. 27. What is the role of screening equipment in the coal conveying system? Answer: To improve the efficiency of coal mills and reduce their wear and tear, it is necessary to crush the raw coal before it enters the mills, reducing it to an appropriate particle size. To enhance the crushing efficiency of the crushers and save electrical energy, screening is carried out first; coal with the correct particle size goes directly into the crushers, and after being crushed to the desired size, it is then fed into the coal mills. 28. What is the function of an iron remover? Answer: An iron remover is used to remove metal particles of various shapes and sizes mixed in coal during transportation, thereby ensuring the safe operation of coal conveyors, coal crushers, and coal grinders. 29. Briefly describe the working principle of a belt conveyor. Answer: When a belt conveyor is in operation, the motor drives the drive roller of the conveyor; through the friction between this drive roller and the belt, the belt moves forward. Materials such as coal are placed on the belt, and they travel together to the discharge point where the coal is unloaded. 30. What are the different types of tensioning devices? What are their characteristics? Answer: There are three types of tensioning devices: tensioning using a weight attached to a tail car, tensioning using vertical rollers with weights, and screw-based tensioning. (1) The weight block type tensioning of the tail car can maintain a uniform tension in the conveyor belt at all times. (2) The spiral tensioning arrangement is compact and requires little space, but it cannot maintain a constant tension. (3) Vertical drum-type weight tensioning device, capable of maintaining constant tension. 31. What are the main components of a screw coal unloader? Answer: The main components of a coal unloader are: (1) the metal frame section. (2) The traveling part of the overhead crane. (3) Screw lifting section. (4) Spiral rotating part. 32. What is the method for replacing the surface roller? Answer: Remove the foot screws, lower it using a crane, position the new roller properly and level it, then tighten the screws. 33. What is the purpose of installing a sieve on the coal drop tube in front of the coal crusher? Answer: It is to ensure that coal with the appropriate particle size is sent directly to the coal grinder, while coal that does not meet the requirements is passed through the sieve and sent to the coal crusher for crushing before being fed into the coal grinder. This improves the crushing efficiency of the coal crusher and saves electrical energy. 34. What is the overall structure of a ring coal crusher? Answer: A ring coal crusher consists of a housing, a cover, crushing plates, rocker arms, a sieve plate regulator, a coal shifter, toothed ring hammers, sieve plates, a main shaft, an annular shaft, ring hammers, and impact plates. 35. What are the allowable angular displacement and radial angular displacement of a coupling? Answer: When there is no radial displacement between the centerlines of the two shafts, the difference in alignment between the couplings represents the allowable angular displacement; when there is no tilt between the centerlines of the two shafts, the radial displacement of the couplings is referred to as the radial angular displacement. 36. What are the structural features of planetary cycloidal pinwheel reducers? Answer: The main advantages of planetary cycloidal pinwheel reducers are their high gear ratios and high efficiency; under the same gear ratio conditions, their weight is 1/2 to 1/6 less than that of conventional reducers. 37. What is the operating clearance of a rolling bearing? What is the relationship between the operating clearance and the fit clearance? Answer: The operating clearance of a rolling bearing refers to the clearance present when the bearing is in use. When the bearing is in operation, the operating clearance is smaller than the fit clearance due to the temperature difference between the inner and outer rings ； Furthermore, due to the effect of rotational centrifugal force, elastic deformation occurs between the inner and outer rings of the rolling elements, resulting in a working clearance that is larger than the fit clearance ； Under normal circumstances, the clearance at work is greater than the fit clearance. 38. What are sealing and sealing devices? Why is sealing necessary? Answer: Sealing refers to the use of appropriate measures to prevent the leakage of liquids or gases at the contact point between two parts. A complete structure designed for sealing is known as a sealing device. Hydraulic machinery, chemical processing equipment, and similar systems often experience leaks during operation, which leads to waste of resources and energy as well as environmental pollution. It also causes unstable operation of the equipment and poses a risk to both human safety and the integrity of the equipment; therefore, sealing measures must be employed. 39. What is standard coal? Answer: Coal with a base lower calorific value of 7000×4.1868 kJ/kg is called standard coal. 40. What is combustion? Answer: Combustion is a process in which the combustible components in a fuel undergo a vigorous chemical reaction with oxygen in the air, releasing heat in the process. 41. What are the elemental analysis components and industrial analysis components of coal? Answer: The elemental analysis of coal includes seven elements, namely carbon (C), hydrogen (H), oxygen (O), nitrogen (N), sulfur (S), moisture (W), and ash (A). 42. What is spontaneous combustion of coal? Explain its causes and outline the main measures that can be taken to prevent spontaneous combustion of coal stored in piles. Answer: When coal comes into contact with air and undergoes slow oxidation, the heat generated must be dissipated promptly; otherwise, the temperature will rise, accelerating the oxidation of the coal and generating more heat. When the temperature reaches the ignition point of the coal, combustion occurs, and this phenomenon is known as spontaneous combustion of coal. To prevent spontaneous combustion of coal stored in coal yards, it is primarily necessary to improve the management of such stored coal. Based on the storage period specified by coal quality standards, the coal should be stored in batches and retrieved in sequence. Additionally, the coal piles should be compacted as much as possible. For coal that is stored for extended periods, heat dissipation measures should be taken depending on the circumstances, such as installing ventilation pipes, turning the pile over regularly, and compacting it to seal it off. 43. What is the basic principle for setting up interlocks between various devices in the coal conveying system? Answer: The basic principle is that, under normal conditions, the operation of devices must be stopped in the direction of the coal flow ； At startup, start the equipment in the opposite direction to the coal flow. 44. What does the inspection and acceptance of belt conveyor systems mainly involve? Answer: It mainly refers to the inspection and acceptance of gears, pulleys and sprockets, bearings, couplings, brakes, reducers, idlers, motors, and belts. 45. What is standard coal? Answer: Coal with a base lower calorific value of 7000×4.187 M/kg is called standard coal. 46. What are the composition benchmarks for coal? Express the percentage content of carbon using each benchmark. Answer: The basis values for the composition of coal include the as-received basis, the analytical basis, the dry basis, and the combustible basis. The percentage content of carbon can be expressed as Cr, Cf, Cs, and Cl respectively. 47. Describe the characteristics of anthracite, bituminous coal, subbituminous coal, and lignite. Answer: Bituminous coal has a high carbon content, low volatile matter, is difficult to ignite, and does not tend to caking. Bituminous coal has a lower carbon content and a higher volatile matter content; most bituminous coals ignite easily and produce long flames. However, low-quality bituminous coal has a high ash and moisture content, resulting in low calorific value and difficulty in ignition; most bituminous coals also exhibit strong caking properties. Lean coal has characteristics that lie between bituminous coal and anthracite: it has a low volatile matter content and is difficult to ignite, but it is slightly better than anthracite. Lignite has a low carbon content and high volatile matter, making it very easy to ignite with a long flame. The oxygen content, moisture, and ash content are all high, while the calorific value is low. 48. List several types of gearboxes used in coal conveying systems and indicate their codes. Answer: There are cylindrical gearboxes, arcuate toothed cylindrical worm gearboxes, worm and worm gear assemblies, planetary gearboxes, and cycloidal pinwheel gearboxes. Taking gear reducers as an example, there are three types: single-stage (9ZD), two-stage (ZL) reducers, and three-stage (ZS) reducers. Lb3C3038: Describe the role of lubrication. Answer: Lubrication plays an important role in the proper operation and maintenance of mechanical equipment. It can control friction, reduce wear, cool down, prevent rust and corrosion on the friction surfaces, provide sealing, transmit power, and reduce vibrations. 49. What is the principle of self-aligning of auto-aligning idlers? Answer: When the belt deviates from its path, the edge of the conveyor belt comes into contact with the vertical rollers that are suspended outside the return frame. When these vertical rollers are subjected to the force exerted by the belt edge, they exert a torque on the rotating frame, causing it to rotate by a certain angle, thereby achieving self-aligning. 50. What are the characteristics of the herringbone-grooved drive drum? Answer: The herringbone-grooved drive drum has a high friction coefficient, which reduces belt tension and extends its service life. The grooves prevent water films from forming, ensuring good driving performance even in particularly humid environments. Additionally, the drum’s bonding process is simple, making on-site maintenance convenient. 51. Explain the reasons why the entire belt deviates to one side and the methods for dealing with it. Answer: The reasons and solutions are: (1) The center of the drive drum is not perpendicular to the center of the belt. Solution: Move the bearing housing position to adjust the center. (2) The idler bracket is not perpendicular to the belt. Solution: Adjust the bracket. (3) The center of the driven drum is not perpendicular to the center of the belt. Solution: Adjust the center. (4) Coal accumulation is adhered to the surfaces of the driving or driven drums and idler rollers. Handling method: Remove accumulated coal. (5) The belt joint is misaligned. Solution: Reconnect the connector. (6) The material falls off at a position offset from the center of the belt. Solution: Modify the coal discharge pipe or install baffles to ensure that the material falls at the center of the belt. (7) Debris is jammed. Solution: Remove debris. 52. Describe the inspection criteria, quality standards, inspection methods, and instruments used for the construction and installation of belt conveyor drums. Answer: The error in the longitudinal and transverse centerlines shall be ≤5 mm, measured using a steel tape ； Axial center elevation error: ±10mm, measured using a glass level ； Levelness ≤ 0.5 mm, to be checked with a level ； The center line of the drum shaft must remain perpendicular to the center line of the conveyor belt; this should be checked using a steel ruler after tensioning the cable. 53. Describe the inspection criteria, technical standards, inspection methods, and instruments used for the construction and installation of belt conveyor frames. Answer: Centerline error: ≤0.5% per segment of the frame length, to be measured using a steel ruler ； Elevation error: ±10mm, measured using a glass level tube ； Lateral and longitudinal levelness: ≤2‰; for the length (width) of the frame and the total length, it shall be ≤10 mm, to be measured with a steel ruler after tensioning. 54. Describe the inspection criteria, quality standards, inspection methods, and instruments for the construction and installation of idler rollers in belt conveyors. Answer: The error in center distance should be ±20 mm, to be measured using a steel ruler ； Levelness of upper and lower idler rollers: ≤0.5mm, to be checked with a level ； Height error of the working surfaces of adjacent idlers: ≤2mm, to be measured using a glass level tube ； The bolts connecting the idler frame to the belt frame should be located in the middle of the long holes, and wedge shims as well as anti-loosening shims should be used; this should be checked ； Check that the groove of the idler frame and the shaft head of the idler are fitted tightly and securely, with no looseness. 55. Explain the working principle of a hammer-type coal crusher. Answer: The working principle of a hammer-type coal crusher is as follows: The high-speed rotating hammers move in a radial pattern due to centrifugal force. When coal enters the machine tangentially, some of the coal pieces are crushed by the impact of the high-speed rotating rotor hammers, while in other cases, the impact force generated by the hammers is transmitted to the coal pieces, and these pieces are then crushed by the guard plate located at the upper part of the crusher. Thereafter, the particle size required for grinding between the hammer and the screen plate falls through the openings in the screen plate. 56. Describe the quality standards, inspection methods, and instruments for the construction and installation of the vertical and horizontal centerlines of hammer-type and counterattack-type coal crushers, as well as the levelness of the machine shaft. Answer: The error in the vertical and horizontal centerlines shall be ≤10 mm; a steel tape is used for measurement ； Axle levelness: ≤0.1mm, to be measured with a precision level. 57. What functions does the program control of the coal conveying system have? Answer: Generally, there are mainly the following 6 functions: (1) To start or stop the coal conveying system via a program. (2) A fault triggers a chain reaction that stops the coal conveying system. (3) Procedural coal blending. (4) Automatic position switching. (5) Repeat coal blending. (6) Change procedure. 58. Describe the functions of idlers and tensioning devices for conveyor belts. Answer: The function of idlers is to support the conveyor belt, reduce its operating resistance, and ensure that the sag of the belt does not exceed a certain limit, thereby guaranteeing the balanced operation of the belt. The function of the tensioning device is to ensure that the belt has sufficient tension, thereby generating the required friction between the drive drum and the belt ； Another function is to limit the sag of the belt between the supporting idlers, thereby ensuring the stable operation of the belt conveyor. 59. Describe the working principle of a belt conveyor.
Answer: The working principle of a belt conveyor is as follows: The belt wraps around the head drive pulley and the tail deflection pulley, forming an endless loop. Both the upper and lower sections of the belt are supported by idlers. The tensioning device provides the necessary tension for the belt to operate properly. During operation, the drive pulley transmits motion to the belt through friction between them; materials such as coal move along with the belt. 60. What are the different types of belt conveyors? Answer: Belt conveyors can be classified according to the type of belt used: ordinary belt conveyors, steel cord belt conveyors, and steel rope-driven belt conveyors ； They can be classified into: Type TD62 and Type TD75. 61. What types of self-aligning idlers are generally used on belt conveyors? What are the characteristics of each type of self-aligning idler? Answer: Grooved, unidirectional, automatic self-aligning idlers are commonly used on belt conveyors. Grooved bidirectional reversible self-aligning idlers and flat self-aligning idlers. Slung type self-aligning idler rollers and flat type self-aligning idler rollers have a simple structure, making them easy to install and maintain ； But it can easily wear out the edges of the belt. Slung reversible self-aligning idlers do not wear the edges of the belt, but they have a complex structure and require significant maintenance effort. 62. What is the principle of self-aligning of auto-aligning idlers? Answer: When the belt deviates from its path, the edge of the conveyor belt comes into contact with the vertical rollers that are suspended outside the rotating frame. As these vertical rollers experience friction from the belt edge, they exert a rotational torque on the rotating frame, causing it to rotate by a certain angle. This in turn generates a force in the opposite direction on the belt that has deviated from its path, thereby achieving self-aligning. 63. What are the main components of a belt conveyor for coal transport? Answer: A belt conveyor is mainly composed of the conveyor belt, idlers and frame, drive mechanism, tensioning device, redirecting drums, cleaner, etc. (7) 64. At what angle does a belt conveyor need to be equipped with a braking device? What are the common braking devices used in power plant coal transportation systems? Answer: When the inclination angle of a belt conveyor exceeds 4°, a braking device is generally required to prevent reverse rotation in the event of a shutdown under heavy load. Common braking devices used in power plant coal conveying systems include belt check valves, roller check valves, electro-hydraulic brakes, and electromagnetic brakes. 65. Why are cleaners installed on belt conveyors? Answer: After the belt unloads, small coal particles often stick to its surface; in order to keep the belt clean, cleaners must be installed to clean the surface of the belt. 66. What is belt deviation? Answer: During the operation of a belt conveyor, sometimes the center line of the belt deviates from the center line of the conveyor and moves to one side; this phenomenon is known as belt deviation. 67. What are the advantages of wire rope-driven belt conveyors compared to ordinary belt conveyors? Answer: The advantages of wire rope-driven belt conveyors over ordinary belt conveyors are: (1) Each unit can cover a long transportation distance and has a high transport capacity. (2) Low power consumption and less steel required. (3) It operates smoothly without any deviation. (4) It has a large single-unit length, few unloading operations during processing, is simple to operate, and facilitates automatic control. 68. What components does a hammer-type coal crusher consist of? Answer: A hammer-type coal crusher is composed of a rotor (main shaft, partition plates, disc, sleeve, shaft pins), screen plates, screen plate support adjustment devices, and the frame portion (cover, base). 69. What is the main task of coal management in the fuel processing plant (workshop)? Answer: Ensuring a continuous supply of coal to the raw coal storage is the main task of the fuel processing plant (workshop). 70. How does a boiler convert the chemical energy of fuel into the thermal energy of steam? Answer: The fuel burns in the furnace, releasing chemical energy which is transformed into thermal energy in the form of flames. This thermal energy is then transferred to the boiler’s feed water; the feed water absorbs this heat and evaporates, eventually turning into superheated steam at a certain pressure and temperature, which is then sent to the turbine to generate power. 71. What are the main technical specifications of electronic rail scales? Answer: The main technical specifications of electronic rail scales include the measurement range and the objects to be weighed, measurement accuracy, dynamic weighing speed, and the measurement process. 72. What are the main components of an electronic belt scale? Answer: An electronic belt scale is primarily composed of a scale frame, weighing sensors, speed sensors, as well as various instruments for signal processing. 73. What is the significance of implementing centralized control for the coal transportation system? Answer: By using centralized control for the coal transportation system, it is possible to improve the working conditions for operators, reduce their workload, and increase productivity. It also enhances the safety and reliability of equipment operation. 74. What equipment is included in the control of the coal conveying system? Answer: The control system for coal conveying equipment can be divided into four parts: the control of belt conveyors (including screening, crushing, iron removal, and wood removal equipment, etc.), the control of coal unloading equipment, the control of yard machinery (including bucket elevators or loading/unloading bridges, etc.), and the control of equipment in the coal blending system. The control methods include local manual control, centralized manual control, and centralized program control. 75. What safety measures should be taken when working on electrical equipment that is completely or partially de-energized? Answer: The following measures must be implemented: (1) De-energize the equipment. (2) Test for electricity. (3) Install a ground wire. (4) Hang signboards and install barriers. 76. What are the main types of motor protection devices? Answer: The main ones include inter-phase protection, single-phase ground fault protection, overload protection, and low voltage protection. 77. What is volatile matter? Does it include the moisture in coal? Answer: In the industrial analysis of coal, when coal is heated under conditions free from air, moisture evaporates first. When the temperature rises to 104°C and is maintained for 7 minutes, the organic substances decompose and release various gases; these gases are known as volatile matter. Therefore, volatile matter does not include moisture. 78. What are high and low calorific values? Which type of calorific value is commonly used in power plant boilers? Answer: The high calorific value refers to the maximum possible heat release per unit mass of fuel; it includes the heat of vaporization released when the water vapor produced by combustion condenses back into water. Lower calorific value is the heat released when a unit amount of fuel is completely burned, with the combustion products H2O remaining in a gaseous state. Power plant boilers mostly use low calorific value fuels. 79. What are the fuel basis of application, analysis, drying, and combustibility? Answer: They refer to the different baseline conditions for fuel used when analyzing its various components. Application basis: Based on the coal fed into the boiler equipment. Analysis basis: Coal that has been naturally dried and had its surface moisture removed is used as the reference. Dried basis: Based on coal with its surface and inherent moisture removed. Combustible base: Based on the residue remaining after all moisture and ash have been removed from coal. 80. What are the effects of air entering a hydraulic system? Answer: When air enters a hydraulic system, since the volume of gas is inversely proportional to pressure, the movement of the hydraulic actuator is also affected as the load changes. Furthermore, air is the main cause of hydraulic oil degradation and heating; therefore, air that enters the system should be removed promptly. 81. What is the meaning of the “five fixes” in lubrication management? Answer: The “five fixes” in lubrication management are: (1) Fixing the quality – Use the appropriate types of oil and grease as specified for equipment lubrication; ensure high standards when changing oil or cleaning, maintain proper functionality of all lubrication devices on the equipment, and keep related tools clean. (2) Quantitative — Add oil and grease in the specified quantities. (3) Identify the locations – Determine the parts of the equipment that require lubrication and the specific lubrication points. (4) Regularly—refuel and change oil at specified times. (5) Assign responsibility – Designate a specific person to be in charge for the specified lubrication areas and points. 82. What should be considered in the operation and maintenance of impeller coal feeders? Answer: The following points should be taken into account regarding the operation and maintenance of impeller coal feeders: (1) The oil temperature in the gearbox should not exceed 75°C, and the temperature of the rolling bearings should not exceed 80°C℃ ； Vibration is within acceptable limits, the quality of the lubricating oil is good, the oil levels in all reduction gears are at the specified levels, and there is no oil leakage. (2) There is no shaft shifting, and the shaft seal is tight. The couplings are firmly connected and the guards are in place; there is no friction or knocking sound between the moving and stationary parts. (3) The foundation nuts are not loose or detached. (4) The voltage and current are stable and within the rated values, with no arcing at the slip ring. (5) The impeller ensures uniform coal feeding, stable speed regulation, and good operation of the crane. (6) Carry out tasks such as refueling, cleaning, and regular testing in a timely and thorough manner as required by the procedures. Electrical components should be cleaned and wiped once a week, while debris on the impeller should be removed once per shift. (7) Slip motors should not operate at low speeds for long periods; they generally need to operate at speeds above 450 r/min, otherwise the excitation coil will overheat. 83. What are the general components of a data processing system for electronic rail scales? Answer: A data processing system for electronic rail scales typically consists of an input zeroing device, an analog-to-digital converter, arithmetic circuits, logic control circuits, a digital display for the weight value, and a digital recorder. 84. What is the function of a screw unloader? Answer: Its function is to use the rotation of the augers on both sides, as well as their upward and downward movement and forward and backward movement, to unload coal from trucks into the coal chute. 85. Describe the acceptable range of temperature and vibration levels for the main equipment in the coal conveying system during operation. Answer: (1) The bearings of the coal conveying machinery should be properly lubricated; during operation, the vibration level should be within 0.1–0.15 mm, while the axial movement should be within 2 mm. During operation, the bearing temperature should not exceed 80°C, and that of sliding bearings should not exceed 60°C. (2) When the reducer is in operation, the gear meshing should be smooth without any noise; vibration should not exceed 0.1 mm, and shaft play should not exceed 2 mm. The oil temperature of the reducer should not exceed 60°C. (3) During the operation of the coal crusher, the amplitude value should not exceed 0.1 mm; otherwise, the cause should be identified and the vibration eliminated. (4) There is no oil leakage at the various hydraulic components and pipe connections in the hydraulic system; the moving rod is not deformed and functions smoothly; the seals have no longitudinal cracks, and the hoses show no signs of aging. The oil pump is oriented correctly, operates without noise, and its vibration does not exceed 0.03–0.06 mm. 86. What are the main types of interlocks for coal conveyor belts? Answer: (1) The coal conveyor belt is equipped with interlocks that prevent the mechanical equipment intended to start from doing so if the audible signal is not activated, or if it does not sound for the required duration. (2) Interlock to prevent mechanical equipment from starting in the wrong sequence. For example: the interconnection between the upstream belt and the downstream belt, starting from the raw coal bin; if the upstream belt does not start, then the downstream belt cannot start either (except for the coal crusher). (3) Accident chain reaction: that is, when any mechanical equipment in the system shuts down urgently due to an accident, the coal conveyor belt running from the point of the accident to the coal receiving area stops automatically. 87. What are the common acoustic alarm signals used in the programming of coal conveying systems? Answer: The common acoustic alarm signals include: when the belt deviates from its path during operation, when the belt slips, when the coal discharge pipe gets blocked, when the motor fails and shuts down, when the belt is torn longitudinally, when there is an incorrect coal level indication in the coal bin, or when the system stops due to a fault on-site. In such cases, the corresponding indicator lights on the control panel will turn on, the associated equipment on the panel will flash to indicate an accident, and at the same time, a horn will emit an acoustic alarm signal. 88. What is the basic principle for setting up interlocks on various devices in the coal transportation system? Answer: The basic principle is that, under normal conditions, the devices must be stopped in the direction of the coal flow ； At startup, start the equipment in the opposite direction to the coal flow. 89. What is the policy for safe production? Answer: The policy for safe production is “safety first, prevention first”. 90. What is the three-level safety education for enterprises? Answer: The three levels of education are: factory-level education, workshop-level education, and team-level education. 91. What is the policy for fire prevention work in our country? Answer: The policy for fire prevention work is “to give priority to prevention and use suppression as a supplementary measure”. 92. What are the three types of safety inspections stipulated by the State Council? Answer: Safety inspections come in three forms: regular inspections, specialized inspections, and seasonal inspections. 93. What is an absolutely safe voltage? Answer: An absolutely safe voltage is one below 12V. 94. What are the different forms of electric shock? Answer: There are the following forms of electric shock: (1) Single-phase electric shock. (2) Two-phase electric shock. (3) Step voltage electric shock. 95. What is working at height? Answer: Any work carried out at a height of more than 2 meters above the ground should be considered as working at height. 96. What is a equipment accident? Answer: Losses resulting from the damage to mechanical and electrical equipment, pipelines, buildings, etc., caused by various reasons are referred to as equipment accidents. 97. What are the three types of industrial waste? Answer: The three types of industrial waste refer to industrial wastewater, waste gas, and waste residues. 98. What are the health standards for industrial noise? Answer: For newly established or expanded enterprises, the allowable noise level during 8 hours of work is 85 dB; for existing enterprises, this limit is temporarily set at 90 dB for 8 hours of work. 99. What is noise? Answer: Any sound that people do not need is called noise. Internationally, decibels are commonly used as the unit to measure the volume and intensity of sound. 100. What is safety management? Answer: Safety management refers to a series of management activities carried out to ensure that production can take place in a favorable environment and with proper order, in order to prevent accidents involving people and equipment, and to safeguard the personal safety of workers as well as the safety of equipment during the production process. 201. What damage can occur if a steel-ring type spiral cleaning idler does not rotate for an extended period of time? Answer: The belt wears out, reducing cleaning efficiency. In severe cases, it is possible to scratch or cut the belt ； The sticky coal gets caught in the drum or weights, causing the belt to deviate from its path. 202. The belt does not deviate when idling, but it deviates when coal is fed in. What is the reason? Answer: 1) The belt is too loose ； 2) Incorrect coal dropping point: 3) Deviated guide chute ； 4) Coal sticking to the drum. 203. What type of idler rollers are installed within the operating area of the iron remover, and why? Answer: Magnetic-resistant drums and magnetic-resistant idlers ； If non-magnetic idlers are used, the idlers become magnetized and are attracted by magnetic separators, which affects safe operation ； Magnetizing the idler rollers increases the iron removal resistance of the iron remover. 204. Do brakes and regenerators serve the same purpose? What belts have brakes installed on them, and on which belts are brakes fitted? Answer: They are not the same. Brakes are generally used for inertial braking; they are installed between the motor and the hydraulic coupling, as well as on horizontally arranged conveyor belts (they can also be installed on belt conveyors with dual drive units at both ends) ； The function of a check valve is to prevent the belt conveyor from reversing after it stops, and it is generally installed on belt conveyors that are arranged at an angle. 205. What type of idler rollers are used at the head of the conveyor belt, and why? Answer: Transition idler. Transition idlers are used to gradually change the belt from a trough shape to a flat one, thereby reducing belt bending fatigue, increasing the wrap angle between the belt and the drum, and ensuring sufficient friction. 206. What is the function of the clearance cleaner, and where is it generally installed? Answer: It is used to remove material adhering to the non-working surface, preventing it from entering the rear drum or the tensioning drum of the vertical tensioning device. It is generally welded to the intermediate frame in front of the rear drum and the tensioning drum of the vertical tensioning device, with the length of the suspension chain being adjusted accordingly. 207. Under normal circumstances, why is it not allowed to stop the coal crusher from operating? Answer: To prevent substandard coal particles from entering the raw coal bin directly in their large pieces, without being crushed or removed first, which could damage the coal grinder or affect its normal operation. 208. What protections does a coal crusher have? Answer: Over-vibration and over-temperature protection are available, and the hydraulic coupling is equipped with a fuse for overload protection. 209. What are the consequences of clogged sieve plates in a roller screen? Answer: 1) Reduce screening efficiency and increase the output of the coal crusher ； 2) It can cause the sieve to overload and shut down, leading to the shutdown of upstream equipment due to excessive load ； 3) In severe cases, it can damage the screening motor, and even cause the screening plates to fall off, leading to equipment damage. 210. The duty officer noticed that the particle size of the coal on belt #5 had increased significantly. Please analyze the reasons. Answer: 1) The baffle of the roller screen is not in place, resulting in a gap on the bypass side ； 2) The sieve plates of the roller screen are severely worn or have fallen off ； 3) The ring hammers of the coal crusher are severely worn ； 4) Improper adjustment of the sieve plate gap in the coal crusher ； 5) The grid holes of the coal crusher screen are broken. Why are herringbone rubber-covered drums used for the drive drum at the head of the conveyor belt? If the rubber surface is worn 211., what harm does this cause to the belt in severe cases? Answer: Herringbone rubber-covered rollers are used to increase the friction coefficient between the belt and the rollers, thereby breaking up any water film and preventing the belt from slipping. The friction coefficient of the rubber surface decreases, causing the belt to slip. 212. What are the hazards of a conveyor belt weight hammer being too light or too heavy? Answer: 1) The weight of the belt counterweight is too low, causing the belt to drift and slip, as well as preventing the belt from starting ； 2) An overly heavy belt weight can cause excessive tension in the belt, leading to its rupture and increasing the load on the motor. 213. When carrying out maintenance work on-site, can a pull-cord switch be used as a safety measure to control the equipment during maintenance? Why? Answer: No ； The pull-cord switch can only be used for emergency shutdown in case of an accident. If it is used for shutdown during maintenance and does not meet safety regulations, the pull-cord switch for shutdown will generate an alarm signal, preventing other devices in the system from operating. If the reset function of the pull-cord switch fails, the conveyor belt remains in standby mode, which can lead to incorrect operations by operators and pose a risk to maintenance personnel. 214. After maintenance, the belt needs to be tested in operation on a single machine – what tasks should the duty officer carry out? Answer: 1) Conduct inspections before starting the equipment in accordance with the procedures ； 2) Switch the local control box switch for the belt to the “local” position, inform the programming staff to “unlock” the belt, press the “pre-start” button, and then start it ； 3) Operation should be stopped immediately if any abnormality is detected. 215. What is the reason why the water bath dust collector results in the discharged air containing a large amount of dust? Answer: 1) The relief valve is damaged, causing the water level to be too high ； 2) There is no water in the dust collector or the water level is too low ； 3) The sewage discharge valve does not close properly, preventing the water level from reaching the operating level ； 4) Air intake duct leakage ； 5) The water baffle has fallen off. 216. What are the reasons for ash emission from the exhaust duct of a bag filter? Answer: 1) The fabric bag is worn out, with holes appearing ； 2) Severe dust accumulation in the bag ； 3) Holes appeared due to corrosion of the steel plate supporting the bag cage. Which areas are prone to belt rupture accidents, and why is it necessary for the programmed duty officers and inspectors to pay attention to checking these areas? 217 Answer: Conveying trough, coal dropping pipe, coal distributor, tensioning drum, tail drum. 218. What safety measures must be taken when entering the coal bin to clean the coal? Answer: 1) Close the outlet baffle of the coal bin, cut off the power to the corresponding conveyor belt, and hang a warning sign. 2) Staff should wear masks and gloves, tie up their sleeves and trouser legs, and use a safety belt when entering the coal bin. The rope of the safety belt must be attached to an external fixing device, with at least two people monitoring from outside. Once inside the coal bin, the safety belt should remain slightly tightened by the supervisor, and staff should use ladders to go up and down. 3) If coal accumulates on one side of the coal hopper and forms a steep slope, that slope should be removed before the coal enters the hopper. 4) Take safety measures to prevent foreign objects from falling into the coal bin through grates or manholes. 5) Detect the concentration of harmful gases and oxygen level in the coal bin. 219. What should a bucket wheel loader operator do when a collapse at the coal yard presses down on the bucket wheel? Answer: It is strictly prohibited to operate the tilting and rotating mechanisms. If there is not much coal accumulated in the bucket, stop the bucket wheel immediately and retract the main frame. If buried in large quantities, manual cleanup is required. 220. What are the limit protection mechanisms available in bucket conveyors, and what is the purpose of these limits? Answer: The bucket wheel conveyor is equipped with protection against belt deviation, slippage, and tearing ； Protections against collisions for the forearm frame, protection for the rotation limits and track area, limits for the upward and downward movement of the cantilever, as well as limits for forward and backward movement. 221. Why must the rotation of the bucket wheel conveyor be within specified limits? Answer: 1) To prevent damage to the railings, floor conveyors, and coal yard facilities ； 2) Prevent the cables at the center from being torn due to excessive rotation ； 3) Prevent damage to the rear vehicle’s equipment. 222. Why is it required that the angle between the cantilever frame and the ground conveyor be less than 300 degrees when the bucket wheel conveyor is used for rapid shunting? Answer: To ensure the stability of shunting operations and prevent the bucket wheel loader from derailing or tipping over. 223. Inspection requirements for the conveyor belt cable reel mechanism. Answer: Regularly inspect the cable reel mechanism; check whether its surface is scratched, crushed, or fractured, whether there is any jamming in the reel, and whether the reel rotates smoothly and in sync with the movement. 224. Requirements for parking bucket trucks. Answer: 1) Place the bucket wheel facing the wind on top of the coal pile; it is strictly prohibited to have it suspended above the ground conveyor belt or with its arm in the air ； 2) Deploy the rail clamps and anchors ； 3) Cut off the control power supply and stop the oil heater ； 4) The cab doors and windows are closed and locked. 225. Why is it strictly prohibited to start conveyor #3 during the process of replacing the tail car of the bucket wheel crane in a limited liability company? Answer: To prevent the tail car from colliding with the equipment due to tension when starting the belt. 226. What effects will an overly loose or overly tight brake in the traveling mechanism of a bucket wheel loader have on its operation? Answer: 1) If it is too loose, the brake will cease to function, and the conveyor’s bucket wheel will be unable to pick up coal ； 2) Excessive tightness makes it difficult for the entire machine to move; the increased resistance can overload or even burn out the drive motor, and may also cause the machine to get stuck on the tracks or overturn. 227. What does the programmed duty operator use to determine the system operation mode? Answer: Based on the operation of equipment in the coal transportation system, its availability, the status of equipment defects, coal quality requirements, the economic efficiency of operating modes, and arrangements from higher-level authorities. 228. What is the spontaneous combustion of coal? Answer: When coal oxidizes in air, the heat generated cannot dissipate outward and accumulates within the pile of coal. As a result, the temperature inside the pile rises continuously until it reaches the ignition point, causing the coal to burn on its own; this phenomenon is known as spontaneous combustion of coal. 229. What is the function of lubrication? Answer: Lubrication plays an important role in the proper operation and maintenance of mechanical equipment. It helps to control friction, reduce wear, cool down components, prevent rusting of the friction surfaces, provide sealing, transmit power, and reduce vibrations. 230. What are the high calorific value and low calorific value of coal? Answer: The heat released when one kilogram of coal burns completely, with the water in the combustion products remaining in liquid form, is known as the high calorific value. The calorific value when the water in the combustion products remains in a gaseous state is called the lower calorific value. 231. What is the function of the emergency pull-cord switch in the coal conveying system? Answer: The emergency pull-cord switch is a device designed for on-site operators to use in order to stop the operation of equipment at any time when a fault is detected or when there is a threat to human safety. 232. What is the proportion of coal in power generation costs? Answer: Coal is the main fuel for thermal power plants, and the cost of fuel accounts for about 70% of the electricity generation costs. 233. What is gear transmission? Answer: Gear transmission is a type of meshing transmission in which two or more gears working together transfer the power and motion from the driving shaft to the driven shaft through mutual meshing. 234. What is the function of a bearing? Answer: Bearings are components used to support shafts; sometimes they can also support components that rotate around a shaft. 235. What are the different types of tensioning devices for belt conveyors, and what are their respective characteristics? Answer: The tensioning devices for belt conveyors include weight-driven tensioning devices, screw tensioning devices, and automatic tensioning devices. Features: 1. The weight hammer tensioning device can maintain uniform tension on the conveyor belt at all times ； 2. The screw tensioning device has the advantage of a short tensioning stroke, but it cannot maintain a constant tension automatically ； 3. The automatic tensioning device is quite excellent, as it can automatically apply even tension in response to changes in load. 236. What is screening? Answer: Screening is the process of using a perforated screen surface to separate materials based on their particle size. Crushing is the process of using mechanical force to overcome and break the intermolecular forces within a material, thereby splitting large pieces into smaller ones. 237. What is the function of the idler rollers in a belt conveyor? Answer: The function of idler rollers is to support the conveyor belt, reduce the resistance to its movement, and keep its sag within a certain limit, thereby ensuring smooth operation of the belt. 238. What is the function of the tensioning device in a belt conveyor? Answer: The tensioning device serves to ensure that the belt has sufficient tension, thereby generating the necessary friction between the drive drum and the belt. Another function of it is to control the sag of the belt between the supporting idlers, so as to allow the belt conveyor to operate properly. 239. What are the main components of an impeller coal feeder? Answer: The impeller coal feeder consists of a main drive mechanism and a crane drive mechanism. 1) The main drive system consists of a drive motor, a safety coupling, a reducer, cross-beam gears, bevel gear reducers, and impellers. 2) The traveling mechanism consists of a traveling motor, a reducer, gear couplings, wheel sleeve couplings, etc. 240. How many stages are there in the crushing process of materials by a ring coal crusher? Answer: The crushing process of a ring-type coal crusher can be divided into two stages. In the first stage, large pieces of coal are crushed by the impact force exerted by the coal crushing plates on the screen plate and the ring hammers ； In the second stage, the small coal pieces continue to be crushed on the screen under the rotation of the rotor and the continuous movement of the hammers; rolling, shearing, and grinding actions further take place to achieve the desired particle size, after which they are discharged through the openings in the screen. 241. What are the basic principles for setting up interlocks between various equipment in the coal conveying system? Answer: In the event of a fault, all operating equipment from the point of failure to the coal supply source must be stopped automatically; in the case of a fault that does not affect the coal crusher, the coal crusher does not need to be included in the fault shutdown interlock. Under normal operating conditions, the equipment should be started in the opposite direction to the coal flow, and stopped in the direction of the coal flow. Under program-controlled operation, the coal crusher can be started first and stopped last; otherwise, the proper functioning of the coal conveying system cannot be ensured. 242. What are the main protection devices for motors? Answer: The main types include interphase protection, single-phase ground protection, overload protection, and low voltage protection. 243. What information should the coal transfer duty officer report to the shift leader or the control room after conducting the handover inspection? Answer: It is necessary to report in a timely manner on the equipment’s operation during the previous shift, its maintenance and standby status, the cleanliness of the site, and the status of the personnel on duty. 244. What are the reasons for the excessively large particle size of the output from a hammer crusher, and what are the solutions? Answer: Reason: 1) There are broken parts in the holes of the sieve plate grid ； 2) Excessive gap between the hammer head and the sieve plate ； 3) Excessive wear of the hammer head and sieve plate. Treatment: 1) Replace the sieve plate ； 2) Adjust the gap ； 3) Replace the hammer head or sieve plate. What causes the impeller of the impeller coal feeder to get stuck? How to handle it? Answer: Reason: 1) The fastening screws of the impeller claws are loose ； 2) Severe deformation at the root of the impeller claw ； 3) There are large pieces of debris in the coal. Treatment: 1) Tighten screws ； 2) Replace the impeller claws ； 3) Remove large pieces of debris. 245. What are the reasons for excessive bearing temperature in coal crushers and what are the solutions? Answer: Reason: 1) Damage to the bearing cage or lock sleeve ； 2) Grease contamination ； 3) The clearance of the rolling bearing is too small ； 4) Insufficient grease. Treatment: 1) Replace the bearing or lock sleeve ； 2) Clean the bearings ； 3) Replace the large clearance bearing ； 4) Fill in the lubricating oil. 246. What are the “five simultaneities” that the State Council stipulates should be applied to work safety? Answer: When planning, arranging, checking, summarizing, and evaluating production, safety work is also planned, arranged, checked, summarized, and evaluated simultaneously. 247. How to prevent electric shock accidents? Answer: 1) Strictly implement electrical safety regulations. 2) Earnestly carry out electrical safety education and publicity work. 3) Regularly check for violations and disciplinary issues as well as the condition of electrical equipment. 248. What are the common causes of electric shock? Answer: 1) Improper installation of electrical wiring. 2) Insulation damage of electrical equipment. 3) Violation of safety operating procedures. 4) Lack of knowledge in electrical safety. 249. How to extinguish a fire in an electric motor? Answer: To extinguish a fire in an electric motor, it is necessary to first cut off the power supply to the motor before attempting to put out the fire. Dry chemical extinguishers, carbon dioxide extinguishers, or 1211 extinguishers should be used to put out the fire. 250. What should be done if someone is electrocuted? Answer: When someone is found to be electrocuted, the power supply should be cut off immediately to free the victim from the electric current, and first aid should be provided. When working at heights, care must be taken to prevent falls from great heights during rescue operations. 251. What is tape deviation? Answer: During the operation of a belt conveyor, sometimes the center line of the belt deviates from the center line of the conveyor and shifts to one side; this phenomenon is known as belt deviation. 252. What is automatic coal blending? Answer: By clicking “Program Allocation” on the upper-level computer in the control room, the coal spreader on the conveyor belt in the coal bin will distribute coal according to the level of coal in the bin – giving priority to situations with low coal levels, distributing coal in sequence as the level rises, and handling any remaining coal accordingly. 253. If it is found that the operating current of a certain device is abnormal, how should the programmed duty operator handle it? Answer: 1) During equipment operation, if the current reading suddenly increases or drops to zero, the inspector should be notified immediately to conduct a check; in emergency situations, the equipment operation should be stopped right away. 2) If the current indication of the conveyor belt changes frequently, the duty officer should be notified immediately to conduct an inspection and take appropriate action based on the specific situation. 3) The current of the belt at the next level is normal; however, the current of this belt conveyor is increasing gradually, which may be due to coal blockage. The duty operator should be notified immediately to conduct an inspection and take action, and the programmed control duty operator should immediately switch the industrial television to that equipment ； 4) The current reading of the ring coal crusher changes frequently; the reason should be analyzed. If it is due to overload, the amount of coal fed should be reduced ； If coal gets clogged or something foreign gets stuck, the machine should be stopped for handling ； In the event of an electrical fault, contact maintenance for repair. 5) During startup, if the motor current indicator remains above the rated value for an extended period (usually not exceeding 5 seconds), the startup process should be stopped immediately; the cause should be analyzed and maintenance personnel should be notified to handle it. 254. What tasks should a programmed duty operator carry out before starting the equipment? Answer: 1) In accordance with the team leader’s instructions, determine a reasonable operation method and promptly issue relevant orders to each inspector in order to carry out inspections and preparatory work before the system starts operating. 2) Check that the power connections for each component are correct, in good contact, and that the plugs are properly inserted. 3) Check that equipment in the programming room, such as the CRT, programming main unit, UPS power supply, television monitors, and monitoring manipulators, is in good condition. 4) Check whether the call system of the coal conveying system is in a reliable standby state. 5) Check whether all baffles in the system are consistent with the determined operating mode. 6) Check whether the telescoping device is in its normal working position. 7) Check that the signals from all auxiliary equipment and protection devices are normal. 255. What are the inspection items for belt conveyors during shift handover and operation? Answer: 1) The wiring and grounding of the motor and its electrical equipment must be in good condition. If the motor has been left unused for an extended period of time (especially those located in humid environments), it must be checked by an electrician to ensure that its insulation is satisfactory before it can be used. 2) The oil levels in the reducer and hydraulic coupler are normal, and there is no oil leakage at any of the joints or shaft ends. 3) The foundation screws of the motor and reducer, as well as the connection bolts of each drive drum, are all tight with no signs of looseness. 4) The braking system is flexible and reliable, with no abnormal phenomena; all protective covers and guardrails are intact. 5) All tee baffles are intact and in the correct positions; the electric actuators operate properly, and the limit switches are undamaged. 6) The coal drop pipe is unobstructed, with no coal accumulation or leaks, and there are no debris on the coal grates. 7) All types of idlers are intact and operate smoothly. 8) The vibrator and coal chute clogging protection devices, as well as their electrical wiring, are in good condition, and the switches are in the correct position. 9) The drive drum and redirecting drum are in good condition; there is no coal sticking to the drum walls, and no damage is present. 10) The coal plows are in their raised position, and they operate flexibly and reliably. 11) The belt shows no signs of scratches, tears, or delamination. 12) The bracket is not skewed. The idler frame is free of deformation. 13) There are no foreign objects on or under the belt, and no jamming. 14) All types of sweepers are in good condition and in their correct positions. 15) The tensioning device is in good condition; the weight blocks are not displaced and are arranged neatly, with smooth tracks. 16) All various protective devices are in good condition. 17) The MCC and PC cabinets are in good condition; all indicator lights, switches, and buttons are intact and function reliably. 18) The sealing gasket of the material guide chute is in good condition, with no coal leakage. 19) All jetty areas and transfer stations are well-lit, have adequate lighting, and are kept clean. 20) The public address system and communication signal equipment along the coal transport system are in good condition and functioning properly. 21) The dust collectors and magnetizers on each conveyor belt are in good condition and reliable, ready for operation. 22) The cutting edge of the coal plow is smooth, without any sharp burrs that could pose a threat to the safe operation of the belt; the plow moves up and down smoothly. 23) It is in place, and the protective devices are reliable. 24) The camera and its accessories are in good condition. 25) The positions of all telescopic heads are correct, and the head locking device is in the locked position. 26) When there is water on Belt Conveyor #3, the wiper should be lowered. 256. What is the impact of changes in coal quality and type on boiler operation? Answer: 1) Volatile matter: Volatile matter is the primary indicator for determining the ignition characteristics of coal types. Different coal types have varying volatile matter contents; as the volatile matter content decreases, the ignition temperature of the coal powder increases significantly and its ignition speed slows down. Therefore, the ignition properties of coal depend primarily on its volatile matter content. The higher the volatile matter content, the lower the loss due to incomplete combustion of the ash. In general, as the volatile matter content increases, the ignition speed speeds up and the ignition temperature decreases, resulting in less loss from incomplete combustion of the ash and a lower content of combustible substances in the fly ash. Therefore, the volatile matter content of coal has a significant impact on the selection of boiler equipment design, the layout of heating surfaces, as well as the safe and economical operation of the boiler. Moisture: The moisture in coal is an inert substance. Its presence reduces the calorific value of coal, as coal used for power generation relies primarily on its heat. During combustion, the moisture in the coal absorbs heat and vaporizes, becoming superheated; this not only reduces the efficiency of heat utilization but also lowers the combustion temperature. When water vaporizes, its volume **increases**, which in turn raises the power consumption of the fan. An increase in the moisture content of coal leads to a gradual deterioration in its flowability, which can cause sticking and blockages in the coal drop pipes, feeders, and coal hoppers of the coal transportation system ； An increase in the moisture content of coal also reduces the output of the coal grinder. Ash: The ash of coal is the residue that remains after combustion. As the ash content of coal increases and its combustible components decrease, its calorific value drops, resulting in an increased coal consumption at constant load. Coal with a high ash content delays the ignition time, reduces the combustion temperature, and as a result, lowers the combustion stability of the boiler. An increase in ash content reduces the degree of coal combustion, leading to increased losses due to incomplete combustion ； An increase in ash content leads to higher physical and thermal losses of the ash slag, which has a greater impact on the economic efficiency of liquid slag discharge furnaces ； An increase in ash leads to more severe fouling and wear on the boiler’s heating surfaces. Such fouling and coking severely affect heat transfer in the boiler, causing the exhaust temperature to rise and thereby reducing the boiler’s thermal efficiency. Moreover, increased wear on the heating surfaces shortens the boiler’s service life and poses a threat to its safe operation. The fusibility of ash also has a significant impact on boilers; coal with a high ash melting point can cause difficulties in slag removal in boilers that use liquid slag removal methods. Coal with a low ash melting point can cause coking in the furnace of boilers that use solid slag discharge, thereby hindering the continuous and safe operation of the boiler. 257. What is the impact of changes in coal quality and type on coal transportation systems? Answer: The quality and type of coal used in coal-fired power plants vary. These changes in coal type and quality have the following impacts on the coal transport system: the impact of changes in calorific value on the coal transport system. A decrease in the calorific value of coal leads to an increased consumption of coal, which raises the workload associated with coal transportation. The coal unloading equipment, storage facilities, screening and crushing equipment, as well as the coal conveyor belts may all be overburdened by the increased amount of coal, exceeding their designed capacity; this can disrupt production, place excessive strain on the coal transportation system, reduce the operational efficiency of the equipment, increase the frequency of failures, force a reduction in output, and even lead to the shutdown of the plant. 2) Impact of ash variation on the coal conveying system. Ash in coal is an unwanted component; its density is more than twice that of the combustible materials in coal. It increases the burden on transportation, and transporting the same volume of coal puts excessive strain on the coal transport equipment. Coal with a high ash content is hard in texture, difficult to crush, causes wear on equipment, and increases the maintenance workload for coal transportation equipment. The impact of moisture on the coal transport system; water in coal is also an unnecessary component. The higher the moisture content, the less organic matter there is accordingly. During the use of coal, high moisture content reduces the efficiency of heat utilization and increases the amount of coal that needs to be burned. An increase in the moisture content in coal can cause coal to stick to and clog the coal conveying equipment; in severe cases, it can halt the supply of coal and disrupt production. If the moisture content in coal is above 10%, it will cause self-flowing, making it impossible for the coal feeding equipment to maintain control and affecting production. In the harsh winter, coal with high moisture content will freeze, affecting coal unloading and loading. If the coal contains very little moisture, dust is generated in large amounts during unloading and loading, contaminating the environment. It affects both environmental hygiene and the health of employees. Volatiles and sulfur content have no significant impact on the coal transportation system. However, when using coal with high volatiles and high sulfur content, care must be taken in screening and grinding equipment to prevent explosions and spontaneous combustion. Because both the ignition point of volatile components and that of sulfur are low, they tend to catch fire on their own. 258. What are the components of a hydraulic system? What is each one’s role? Answer: A complete hydraulic system consists of the following components: the power unit. An oil pump is used to convert mechanical energy into hydraulic energy. Operative part. Cylinders and hydraulic motors are used to convert hydraulic energy into mechanical energy. Control section. Pressure control valves, direction control valves, flow control valves, etc., are used to control and regulate fluid flow in order to meet the requirements for transmission performance. Working medium. Oil, used to transmit energy. Auxiliary part. Fuel tanks, oil filters, accumulators, heaters, coolers, pipelines, fittings, hydraulic gauges, etc. For hydraulic systems, some of these auxiliary components are essential, such as oil tanks, pipelines, and pipe fittings, while others are used to improve the quality of the transmission mechanism. 259. What is the purpose of the interlock for the coal conveyor belt? Answer: To ensure safe operation, all the equipment in the coal conveying system starts and stops in accordance with specific operational requirements, thereby checking each other. The coal conveyor belt is one of the main devices that participate in interlocked operation in this way. When general equipment is started, it is activated one by one in the reverse order of the coal flow; whereas when it is shut down, it is stopped one by one in the same order as the coal flow. When a device involved in the interlock operation within the system fails and stops operating, the devices that came before it shut down automatically in accordance with the interlock sequence, while the devices that follow continue to operate, thereby preventing or reducing the risk of coal accumulation and the expansion of accidents within the system. 260. What are the main reasons for severe coal leakage from the coal plow? How to solve it? Answer: Reasons: 1) The plow blade is severely worn or clogged with debris ； 2) The plow blade is not straight or has poor contact with the belt surface ； 3) The plow head does not descend far enough or is tilted ； 4) The guide angle at the rear of the plow blade is too large, or the scraper cannot be retracted ； 5) Severe damage to the belt surface ； 6) The horizontal idlers are uneven or the spacing between them is too large ； 7) The belt shifts towards the discharge side. Solution: 1) Replace the plow blade or remove debris ； 2) Correcting plow share ； 3) Adjust the limit to correct the plow head ； 4) Reduce the guide angle or add additional closing scrapers ； 5) Replace the belt ； 6) Adjust or increase idler rollers ； 7) Alignment adjustment. 261. What are the causes of belt breakage? How to handle it? Answer: Reasons: 1) Poor adhesion quality at the belt joints or severe wear, resulting in delamination or horizontal scratches ； 2) Belt too tight ； 3) High number of starts under load ； 4) Blockage of coal drop pipes and guide chutes ； 5) Severe coal accumulation at the head and tail sections, causing blockages ； 6) The tensioning device fails and gets stuck ； 7) The belt is operating under overload. Solution: 1) Stop operation immediately and re-adhere it ； 2) Appropriately reduce the counterweight ； 3) Avoid starting under load ； 4) Remove coal accumulation and blockages at the coal drop pipes and guide chutes ； 5) Remove coal accumulation at the head and tail to eliminate blockages ； 6) Clear blockage ； 7) Reduce the conveying volume. 262. What are the main aspects of motor operation monitoring? Answer: 1) Does the current exceed the allowable value? ； 2) Is the lubrication of the bearings proper? ； 3) Check whether the motor makes any abnormal noises, and there should be no burnt smell ； 4) Are the ambient temperature and motor temperature rise normal? ； 5) Are the enclosure grounding wires and cable terminal protective covers intact and secure? ； 6) Is the motor vibration normal? Are there any signs of sparking, smoking, dust accumulation, or water accumulation? ； 7) In the event of any abnormal phenomena, it should be reported to the team leader immediately or the electrical staff should be notified to conduct an inspection. 263. To prevent belt tearing, what aspects should be carefully checked before starting? Answer: Before starting the equipment, each inspector should conduct a thorough inspection in accordance with the operating procedures; only after confirming that there are no abnormalities can they notify the programmed duty officer to start the equipment ； Before starting up, it is necessary to carefully check whether the sweepers and coal scrapers are deformed, and whether there are any debris trapped inside the protective covers at their ends. It is also important to ensure that the primary and secondary blades of the wipers and coal scrapers are smooth without any burrs. Check whether the clamps used to hold the guide trough steel plates and the fixing angle irons are loose, and that the distance between the sealing strips and the belts is at least 5 cm. Verify that there are no hardware components or debris inside the drive rollers and other steering rollers. Also, check whether there is any debris on the belts in each circuit (especially those behind the empty-section sweepers). Ensure that none of the idler rollers have misaligned shafts or missing dust covers. Finally, check whether there is any debris inside the guide troughs and coal discharge pipes. Any abnormalities found should be reported to the shift supervisor promptly so that appropriate action can be taken ； 264. To prevent belt tearing, what aspects should be closely checked during operation? Answer: 1) While the equipment is in operation, the duty officer should closely monitor its operating conditions, the flow of coal, as well as any components that may fall off due to vibration. They should also keep an eye on the performance of the cleaners, and check whether the disc and belt type iron removers are successfully removing iron particles. It is necessary to check whether there are any hard objects in the drive and tail rollers. If any signs of belt tearing are detected, the machine should be stopped immediately by pulling the emergency stop cord ； 2. During operation, it is strictly prohibited to overload the equipment. If any abnormal objects or \"four large pieces\" are found on the belt, contact the programming operator promptly. In emergency situations, the emergency stop cord must be pulled immediately to shut down the machine ； 3. When a programmed duty officer receives a report of an abnormal situation from an inspector, they should closely monitor the operation status of the equipment at the relevant stations, and at the same time remind the duty officers at other related stations to pay attention ； The machine should be stopped immediately when an abnormality is detected ； 4. It is strictly prohibited to leave one’s post without permission, wander from one’s assigned area, leave the equipment under one’s supervision without authorization, or engage in any activities unrelated to work while on duty ； 5. In addition to strictly adhering to operational safety measures, the bucket wheel conveyor operator must also strictly follow the safety measures designed to prevent belt tearing ； 6. After the belt starts operating, the programmed duty officer (deputy officer) must pay close attention to whether the direction of coal flow is correct. Once the coal supply equipment begins feeding coal, the monitor screen should be switched to show the coal bin area promptly, in order to prevent blockages in the coal discharge pipes ； 7. During operation, the programmed main and auxiliary operators must pay close attention to whether the current levels of various devices remain within normal ranges. If any abnormalities are detected, they should immediately contact the on-site operator for clarification; in emergency situations, the operation of the equipment must be stopped right away ； 8. Each shift shall conduct tests on the belt tear protection devices as required; any issues found should be recorded promptly, and maintenance personnel should be contacted for handling ； 9. Each team should regularly inspect the steel plates used for alignment adjustment that are welded inside the coal discharge pipes. In the event that the belt suddenly deviates from its path or any other abnormal situation occurs, the machine should be stopped immediately for inspection, to prevent the steel plates from falling and causing scratches or tears in the belt ； 10. Equipment with serious defects (belts that are severely worn and scratched) should be under closer supervision ； 265. What preventive measures does the department take to avoid electric shock injuries and deaths? Answer: 1) Strictly implement the “two tickets, three systems, one form” system, and fill out the power outage/power restoration notification forms in strict accordance with the regulations ； 2. When carrying out tasks related to operation tickets, strictly follow the procedures of \"reciting the instructions, repeating them, and then performing the operations\", as well as the supervisor system ； 3. When carrying out power outage and restoration tasks, it is necessary to follow the prescribed sequence of operations; it is strictly prohibited to perform such tasks without a supervisor present ； 4. When performing power outage and restoration operations, the operators and supervisors must wear clothing that complies with safety regulations, including insulating shoes, insulated gloves, and work uniforms ； 5. When performing power on/off operations or removing/installing fuses, it is strictly prohibited to use both hands, and it is also strictly forbidden for any other part of the body to come into contact with the control cabinet or the building ； 6 Move around on your own ； For 7 motors located in humid areas, it is necessary to first use a voltage tester to confirm that there are no abnormalities before checking their temperature and vibration levels ； 266. Measures to prevent electrical fires in coal transportation systems? Answer: 1) When dust accumulates in all cable trays (inside) of the system, defects should be recorded promptly and maintenance personnel should be contacted to handle it ； 2. When dust accumulates in all control cabinets and MCC cabinets of the system, defects should be recorded promptly and maintenance personnel should be contacted to handle it ； During use, if arcing is observed due to poor contact at the switches and contactor contacts, use should be stopped immediately, and maintenance personnel should be contacted for repairs ； If arcing is observed at the cable connections on site, it should be reported to the team leader immediately, and the relevant maintenance departments should be contacted promptly to handle the issue ； During operation, it is necessary to check the temperature rise of each motor regularly; if any abnormalities are detected, operation should be stopped immediately and maintenance personnel should be notified to handle the issue ； It is strictly prohibited to use copper wire, iron wire, or other metals that do not meet the requirements as substitutes for fuses, and it is also strictly prohibited to use fuses beyond their rated capacity ； 267. What are the measures to prevent track deviation accidents of the impeller coal feeder? Answer: 1) Inspectors should strictly follow the checks to be performed before starting the impeller coal feeder as well as the precautions to be observed during its operation, as specified in the operating procedures ； 2. Before operation, check all protective devices of the impeller coal feeder to ensure their reliable operation ； 3. It is strictly prohibited for the duty officer to leave his post without permission during operation; what are the measures to prevent injuries caused by cleaning the roller screens and coal crushers? Answer: 1) When cleaning the coal crusher and coal screener, it is necessary to take all required safety measures before proceeding ； 4. When cleaning the coal accumulation and debris from coal crushers and screeners, safety measures must be taken; there must be at least one supervisor to prevent 3) the cleaners from falling from the equipment or suffering other injuries ； 5. If it is necessary to enter the coal crusher or coal screener for cleaning due to work requirements, all safety measures to prevent rotation must be taken, and the power supply to the related equipment at various levels must be cut off ； 6. When carrying out cleaning tasks, it is necessary to use safety belts when required, to prevent cleaners from falling from the upper part of the machine ； 7. It is strictly prohibited to insert hands directly into the machine or any part of the body to remove debris ； 8. When debris is found in the coal crusher and coal screener and cannot be removed, notify the maintenance staff promptly to handle it. 268. What are the measures to prevent fires in the MCC cabinets and various local control boxes? Answer: 1) It is strictly prohibited for rinse water to splash onto the MCC cabinets and various local control boxes ； 2. The door of the on-site MCC cabinet must be closed tightly after use ； 3. If smoking or sparking is observed in the electrical equipment within the MCC cabinet during operation, stop the equipment immediately and contact maintenance personnel to handle it ； 4. Regularly check for dust accumulation inside the on-site MCC cabinets; once any issues are detected, record them as defects and contact maintenance personnel to address them, in order to prevent fires in the control panels caused by excessive dust accumulation ； 5. The fuses used in the MCC cabinet must be selected according to the specified capacity; it is strictly prohibited to use iron wires, copper wires, or other metals as substitutes ； 269. Safety measures to prevent coal depletion in the coal bin? Answer: 1. During shift duty, the programmed control operator should promptly verify the actual coal level in the coal bin with the on-site operator, to prevent coal supply interruptions caused by faults in the level sensors ； 2. During their shifts, the shift leaders and programmed control operators should use the MIS at any time to monitor the operation of each grinding unit as well as any changes in their operation, in order to prevent coal supply disruptions in the coal bins due to changes in the grinding units ； 3. It is strictly prohibited to allow any debris to enter the coal bin, to prevent a shortage of coal in the bin due to blockages in the coal feed pipe ； 4. Strictly implement the relevant regulations on using water spraying to control dust in the department, in order to prevent coal from scattering in the coal bins and any situations that could affect the load of the units ； 270. What are the main functions of coal conveying programmable control? Answer: Coal feeding and coal storage control functions ； Coal blending control function ； Monitoring and alarm function, accident alarm function ； Functions for displaying coal level in the coal bin, managing and monitoring it, as well as recording data; accident recall function ； Function for selecting coal feeding and blending methods 271. What is the activation mode for the interlock system of the coal conveying system? Answer: When program interlock automatic control is used, the interlock between devices is automatically activated. When manual control via procedural interlocking is used, the interlocking between devices is activated automatically. When manual control for unlocking is used. Interlock between devices is released. Unlocked operation is not permitted under normal circumstances. In the event of a system failure, the system can be stopped using the local pull-cord switch or the emergency stop button on the operator station (engineer station for maintenance purposes). 272. What are the inspection items for the programmed handover during coal transfer? Answer: The programmed duty operator reviews operation logs, equipment operation records, equipment defects, work orders, and work order records, etc., to understand the operating and standby status of the equipment, as well as its maintenance status; they also check whether the equipment defects and abnormalities match the settings on the operator station (engineer station for maintenance purposes). The power and signal indicators on the programmable control cabinet are normal, and the buttons, indicator lights, and switches on all the panels in the control room are present in full and undamaged. The programmable logic controller (PLC), operator station (engineer station for maintenance purposes) (PC), monitor (CRT), printer, UPS power supply, etc., should be in normal condition and functioning properly. The hosts, keyboards, monitors, mice, UPS units, etc. of each PC are all present and intact, and the television monitoring system is working properly. The equipment was put into trial operation; it started and stopped properly, and operated normally. The coal feeding systems were in place (except for the equipment under maintenance). All displays and electrical panels were functioning correctly. During shift handover when the equipment is operating normally. The ammeter display on the management unit and the industrial TV monitor should be checked in detail; only once it is confirmed that everything is normal can the shift handover be approved with a signature. If any problems arise after the handover, the person taking over will be held responsible. Upon taking over, the coal level in the coal bins was checked; the inspections conducted on site showed that the coal levels were normal, all being above 8 meters, and all the coal scrapers were in the raised position. All consoles, control cabinets, public address systems, air conditioners and other equipment and facilities, as well as tools, are complete, in good condition and operating properly. Verify the data from the electronic belt scale. The door and window glass, as well as the bathroom facilities, are in good condition. The cleaning of the areas under this position’s responsibility meets the standards for civilized production. 273. What are the inspection items before the programmed start of coal transfer? Answer: 1) Based on the supervisor’s instructions, determine a reasonable operation method and promptly issue relevant orders to the various inspectors in order to carry out the inspections and preparatory work before the system starts operating. 2. Check that the power connections for all components are correct, have good contact, and that the plugs are properly inserted. 3. Check that devices in the programming room such as the CRT, programming main unit, UPS power supply, television monitors, and monitoring manipulators are in good condition. 4. Check whether the broadcast calling system of the coal conveying system is in a reliable standby state. 5 Check whether all baffles in the system are consistent with the designated operating mode. 6. Check whether each head telescoping device is in its normal working position. 274. In what situations should the insulation resistance of the motor be measured, and the measured values recorded in detail? Answer: 1) Newly commissioned motors. 2) Motors that are powered on for the first time after maintenance. 3) Motors that have been exposed to water or moisture. 4) When motors that have been without power for more than 5 days need to be powered back on. 5) Motors that trip during operation. 275. What are the precautions for measuring insulation in electric motors? Answer: 1) Check whether the serial number of the measuring equipment is correct. Check that the power supply to the motor has been completely cut off, confirm that there is no possibility of a sudden power restoration, and use a qualified voltage tester to verify that there is no voltage present. Discharge the motor and cable under test. Select the appropriate measuring tool and check that it is in good condition; ensure that no one is working in the circuit. Select a suitable ground point and verify that it is indeed good, then disconnect the circuits that affect the accuracy of the measurement. The insulation measurement time must be no less than 1 minute. After the measurement is complete, discharge the device being measured and restore the circuits that affected the accuracy of the measurement. 276. The basic components and working principle of belt conveyors. Answer: Components of a belt conveyor: A belt conveyor mainly consists of the conveyor belt, drive equipment (motor, hydraulic coupling, reducer, elastic pin coupling), main drive drum, direction-changing drum, tensioning drum, parallel idler sets, trough idler sets, buffer idler sets, trough self-aligning idlers, parallel self-aligning idlers, tensioning devices, cleaners, empty-section cleaners, guide channels, frame, safety guards, head and tail covers, and various protective devices. Working principle: A belt conveyor is a continuous conveying machine that uses a belt for traction and loading to transport bulk materials; in power plants, it is mainly used for transporting coal. The belt wraps around the drive drum, redirecting drum, and tensioning drum to form a continuous loop; it is supported by parallel idlers and trough idlers, and a tensioning device applies a certain amount of tension to keep the belt in close contact with the outer surfaces of these drums. There is a certain coefficient of friction between the outer surface of the drive drum and the belt. As the drive drum rotates continuously, the friction between it and the belt drives the belt to move horizontally, thereby transporting the materials scattered on the belt in a continuous manner. 277. What are the inspections and precautions during belt conveyor operation? Answer: 1) During the operation of the equipment, the inspector must carefully listen to the sounds of the motor and gearbox to determine whether they are normal. 2. Check whether the temperature at each bearing seat is too high and whether the vibration levels exceed the standards; the vibration level at each location should be ≤0.1 mm, the temperature should be ≤800°C, the temperature rise should be ≤400°C, and the axial movement should be ≤2 mm. The temperature of the reducer oil should be ≤600°C, and the temperature of the motor should be ≤800°C. 3. The belt in operation should not deviate from its path; if slight deviation is detected, it should be adjusted promptly. 4. The coal flow on the belt should be normal; it must not operate under overload conditions. If overload is detected, contact the coal conveying control operator immediately to adjust the coal supply rate. 5) During operation, close attention should be paid to the condition of the belt at the outlet of the feed chute and at the discharge point of the conveyor belt. If coal leakage or abnormal coal flow is detected, the cause must be identified immediately and corrective action taken right away. 6. Pay special attention to the coal discharge from the head coal discharge pipe; if blockage is detected in this pipe, the machine should be stopped immediately. 7. Check whether various idlers and rollers rotate smoothly, if there are any abnormal noises, and whether all types of cleaners are functioning properly. If the equipment is not functioning properly, the inspector shall report to the team leader based on the progression of the defect, or stop the operation of the equipment. 8. All coal discharge pipes should be unobstructed with no severe coal accumulation; the duty officer determines the operating mode and frequency of the vibrators based on the quality of the coal. 9. The tensioning device is operating properly; the weight should not reach its extreme position, the tracks should be smooth without any deformation, there should be no jamming in the ropes or wheels, and the steel cables should not have any short strands. 10. All protective devices shall operate correctly. 11. When a cut on the belt is detected, stop the machine immediately by pulling the emergency stop cord, and report to the shift leader and department supervisor. 12. Check the moisture content of the coal; the dust concentration in the system should not be too high, and adjust the water flow rate of the sprinkling device at the outlet of the material guide chute in a timely manner. The water spray volume must not be too high, so as not to affect the boiler coal grinding system. 13. It is strictly prohibited to operate the telescopic head while it is in operation. 14. It is strictly prohibited to clean the coal stuck on the deflection drum and drive drum while the conveyor is in operation. 15. It is strictly prohibited to clean, sweep, or wipe any rotating parts of the belt conveyor. It is strictly prohibited to clean coal accumulation, dust accumulation, etc. from beneath the belt conveyor. 16. It is strictly prohibited to cross the belt at any time; if it is necessary to pass through, one must use the access bridge. 17. When the sealed leather part moves out, it must not be adjusted by a single person. 18. It is strictly prohibited to use belt conveyors as alternative transportation methods. 19. It is strictly prohibited to start the belt conveyor under heavy load. 20. In case of the following situations, the emergency pull-cord switch should be used to shut down the machine immediately. (1) The motor overheats and starts smoking. (2) There are occurrences that threaten personal safety. (3) Blockage of the coal drop pipe. (4) Scratches or tears in the belt. (5) A fire breaks out in the system (fire on belts, fire in electrical equipment, etc.). 278. The safe operation of the coal transportation system is of great importance for the safe generation and supply of electricity across the entire plant; all employees must attach great attention to it in order to prevent accidents from occurring Answer: 1) Fire in the coal conveying system; 2) Accidents resulting in minor injuries or worse; 3) Prolonged tearing of conveyor belts; 4) Empty coal storage bins; 5) Damage to key equipment in the system; 6) Disruption of all methods for feeding coal into the system; 7) Entry of large objects into the coal storage bins, causing the boiler’s coal mills to stop operating. 279. What are the general principles for handling faults in the coal conveying system? Answer: As the first stage in thermal power generation, the coal transport system requires the fuel department to strictly adhere to the principle of \"safety first, prevention foremost\" in order to ensure its safe, economic, and stable operation. In the event of any abnormalities or failures in the equipment or system, it is necessary to address such issues promptly, always prioritizing the protection of personnel, equipment, and the power grid. 1) When a equipment failure occurs and the equipment can no longer operate, it is necessary to report to the shift supervisor as well as the company’s and department’s on-duty managers first, and take active steps to restore system operation in order to ensure a supply of coal for the boiler. If equipment failures or potential hazards are detected, they should be reported to the shift leader and the programming operator promptly so that the cause of the failure can be identified as soon as possible. Enter equipment defects into the MIS in a timely manner and contact the maintenance department to resolve them. For equipment that has been shut down due to a fault, no one shall restart it until the cause is identified and the defect is resolved. Equipment that must operate despite having defects should have appropriate safety measures put in place based on the nature of those defects, in order to prevent them from worsening. After an accident occurs, the relevant teams must take proactive remedial actions to prevent the accident from spreading. All relevant personnel must cooperate in a practical and honest manner with the departmental or company officials to conduct accident investigations and analyses in accordance with the principle of \"not letting anything go unchecked.\" 280. What is the device number of the system? Answer: Based on the characteristics of the equipment and process flow in the coal transportation system, numbering is done in the order of the flow direction. The System A and System B do not intersect; when standing between the two devices facing the direction of the flow, the right side corresponds to System A, while the left side corresponds to System B. The number of the coal plow corresponds to the unit and the coal bunker. 281. What are programmed automatic coal blending, programmed manual coal blending, and on-site manual coal blending? Answer: For the programmable automatic coal blending method: By clicking “Programmable Blending” at the operator station in the control room (engineer station during maintenance), the coal spreaders on the conveyor belts of the coal bins will fill the bins from bottom to top, depending on the level of coal in each bin (except for the maintenance bin). The programmed duty operator then manually activates another belt conveyor in the coal bin using program-controlled interlocking, and by clicking on the “Program Allocation” system, the coal is allocated to the bins in order, starting from the lowest bin first and moving to the higher ones. Programmed manual coal blending: On the operator station in the control room (engineer station during maintenance), click “Manual blending” to perform individual up and down movements of the coal spreader, thereby filling all the coal bins. On-site manual coal blending: This involves operating the coal spreaders one by one right at the equipment location, with manual monitoring of the coal level in the silos to ensure that they are filled to capacity. 282. What are the inspection items after the conveyor stops? Answer: 1) Check that all parts of the conveyor belt are undamaged. 2. Check each drum for coal sticking; if there is coal stuck, stop the machine and clean it. 3. Clean the hygiene on the cleaning drive device. 4. Inspect and clean the coal chute and coal grates of any stuck coal and debris. 5) Check whether the belt is scratched and whether the joints are in good condition. 6) Check whether all auxiliary equipment is in normal condition and intact, and whether the water, heating, electricity, and lighting systems are functioning properly. 7) Upon discovering equipment defects, contact the coal transfer control operator promptly and fill out an equipment defect form. 8) Keep the area under one’s responsibility clean. 283. What are the basic components and working principle of a coal crusher? Answer: Composition: The ring-type coal crusher is mainly composed of a housing, a cover, impact plates, rocker arms, a screen plate regulator, a main shaft, an ring hammer shaft, gear rings, rings, screen plates, coal crushing plates, an iron removal chamber, a hydraulic system, a hydraulic coupling, a motor, etc. Working principle: It primarily uses the hammer rings on the high-speed rotating rotor to apply hammering force in order to break up coal lumps. When these coal lumps enter the coal crusher chamber, they are struck by the rapidly rotating rings and toothed rings and pressed against the crushing plate. The coal is broken down through shearing, compression, rolling, and grinding by the hammer rings. Indestructible materials such as iron and wood are carried by the toothed rings to the iron removal chamber. The crushed coal passes through the holes in the screening plate and enters the coal discharge pipe, thus completing the entire process of coal crushing. 284. Inspections and precautions during the operation of coal crushers: Answer: 1) The inspector should regularly check the temperature and vibration at each bearing seat while the equipment is in operation. The temperature rise of the main bearing ≯ 400°C; the maximum temperature ≯ 800°C, and the maximum amplitude ≯ 0.03 mm. There is no powder or coal leakage at various inspection doors and the door to the iron removal chamber, and no oil leakage from the hydraulic coupler. Check whether the coal delivery pipes at the top and bottom are leaking coal. Check whether there are any abnormal noises inside the coal crusher, at each bearing seat, and in the motor. After the maintenance of the next level of belts (replacing the sealing material for belt #5), it is even more necessary to pay close attention to the coal feeding and discharging conditions of the coal crusher. Upon detecting a blockage, stop the machine immediately; it can be restarted only after identifying the cause. It is strictly prohibited to open the inspection door or the door of the iron removal chamber while the equipment is in operation or before it has come to a complete stop. It is strictly prohibited to rinse the motor directly with water. It is strictly prohibited to clean or wipe the rotating parts of the equipment while it is in operation. It is strictly prohibited to enter the coal crusher to carry out tasks such as cleaning or maintenance without proper safety precautions. It is prohibited to start the coal crusher under load. 285. What are the basic components and working principle of the impeller coal feeder? Answer: Basic components: The impeller coal feeder is mainly composed of a frame, a main drive system, a traveling drive system, a remote control device, a control box, and a dust removal system. The main drive system consists of a motor, reducer, drive shaft, impeller, electrical speed control system, etc ； The traveling drive system consists of a motor, a reducer (pinion cycloidal), traveling wheels, couplings, etc. Working principle: The motor is driven by an electrical control box; through a reducer and a drive shaft, the impeller inserted into the gap of the coal unloading chute rotates, causing the leaf claws to move in a rotational motion that pushes the coal out of the chute. The coal then falls onto the belt conveyor below via a coal discharge pipe. During the coal feeding process carried out by the impeller feeder, it is possible to feed coal while the machine remains in place, or it is also possible to feed coal while the machine is in motion. The movement of the entire unit is achieved by the forward and reverse rotation of a motor with a constant speed. When the impeller coal feeder reaches one of the ends or when the two impeller coal feeders come close to each other, their travel switches or proximity switches activate, causing the impeller coal feeder to operate in the reverse direction automatically. The speed of the impeller is controlled by an inverter, which enables the coal feeding amount of the impeller coal feeder to be adjusted. 286. What are the precautions for operating the impeller coal feeder? Answer: Whether the impeller coal feeder is operated locally or remotely via program control, the following operating methods are strictly prohibited (except in abnormal situations): 1) It is strictly forbidden to change the direction of movement of the impeller coal feeder while it is in motion. When it is necessary to change the direction of travel, the traveling system must first be stopped; then, pressing the button corresponding to the opposite direction will cause the equipment to change its direction of travel. It is strictly prohibited to start the impeller coal feeder without setting the impeller speed to “zero”. It is strictly prohibited to operate the traveling drive system when the coal feeding mechanism is not functioning properly. It is strictly prohibited to activate the impeller coal-shifting mechanism when the lower belt conveyor is not operating properly. It is strictly prohibited to stop the operation of the impeller coal feeder without first setting the impeller speed to “zero”. It is strictly prohibited to stop the operation of the impeller coal feeder while in motion. It is strictly prohibited to place other items on the tracks, such as tools or clothing. During operation, pay attention to checking the coal feeding rate and ensure even coal supply to guarantee normal unloading from the coal chute. 287. What is the composition and working principle of a roller screen? Answer: The roller screen mainly consists of a transmission mechanism and the screen body, as well as an electrical control system. The transmission mechanism is made up of ten sets of motors plus cycloidal pinwheel reducers (for single-axis drive), while the screen body is composed of metal components, shafts (ten in total), and screening elements. The electrical control system includes frequency converters, PLC programmable controllers, and other components. Working principle: The roller screen operates through 10 screening shafts arranged side by side, rotating in the same direction. When the material to be screened (coal) falls onto the first three shafts on the screen surface, it spreads out quickly; the rotating shafts and screen plates then push this material forward, causing it to roll. Meanwhile, the material particles that are smaller than the size of the screen holes fall downward due to their own weight and the rotational force of the screen plates, while those particles that are larger than the screen hole sizes move forward along the screen surface until they reach the outlet of the roller screen and fall into the coal crusher. 288. Basic components and working principle of the bucket wheel conveyor: Answer: Components: The bucket wheel stacker-reclaimer is mainly composed of a cantilever belt conveyor, a bucket wheel mechanism, a rotating mechanism, a tilting mechanism, a traveling mechanism, a tail car mechanism, a gantry frame, a dust removal device, an operator’s cabin, a hydraulic system, power supply units, cable winding mechanisms for communication cables, various protection devices, and an electrical system (upper electrical room and lower electrical room). Working principle: The bucket wheel mechanism is installed at the front end of the cantilevered belt conveyor and rises and falls together with the conveyor in order to accommodate coal at different heights. As the bucket wheel rotates, when the buckets reach the lower portion, they scoop coal into the buckets. As the bucket wheel continues to rotate until it reaches its highest point, the coal falls due to its own weight. An arc-shaped coal deflector then guides the coal into the receiving chute, from which a boom conveyor transports it to the central coal drop pipe. Below the coal dropping pipe is the tail car belt conveyor that is connected to the surface belt; coal falls from the central coal dropping pipe onto this tail car belt conveyor, and from there it is transported via the surface belt to the coal transportation system, thereby completing the material collection process by the bucket wheel conveyor. When stacking coal is required, the tail car is raised to above the cantilevered belt conveyor. The coal supplied by the system falls onto the cantilevered belt conveyor via the surface belt and the tail car belt. The belt conveyor then reverses direction, transporting the coal to the front end where it is deposited in the coal yard, thus completing the stacking process. 289 What are the precautions during the operation of a bucket wheel conveyor? Answer: It is necessary to contact the programmed control operator before stacking or removing coal. It is strictly prohibited to consume alcohol within 8 hours prior to operating the stacker-reclaimer at work. It is strictly prohibited to move the heavy vehicle without activating the audio alarm. It is strictly prohibited to change the operating mode of the bucket wheel conveyor’s tail car while the #3 belt is in use. It is strictly prohibited to start belt #3 during the process of changing the tail car of the bucket wheel conveyor. It is strictly prohibited to move the main crane or start belt #3 until it is confirmed that the tail car of the bucket wheel conveyor is properly connected. When performing rapid shunting with the heavy haul vehicle, the cantilever frame must be positioned at an angle of less than 300 degrees with respect to the conveyor belt track. The coal intake depth of the bucket wheel shall not exceed 1000 mm. It is strictly prohibited to reverse the rotation, movement, or tilt of the bucket wheel loader while it has not come to a complete stop. In winter, when a collapse at the coal extraction site presses down on the bucket wheel, it is strictly prohibited to operate the lifting and lowering mechanism as well as the rotating mechanism. It is strictly prohibited to operate the rotation and tilting mechanisms of the bucket wheel loader while the vehicle is in motion. It is strictly prohibited to operate the bucket wheel conveyor beyond its capacity. It is strictly prohibited for the cantilever frame to pass over the rear vehicle. Before operation, it is necessary to check that all protective devices are in good condition and operate smoothly and reliably before proceeding with the procedure. When electrical or mechanical faults such as those in motors or reducers are detected, the machine must be stopped for repair before operation can resume. The bucket wheel crane operator should conduct a thorough inspection every hour; additional inspections should be carried out when operating the crane while it is malfunctioning. The main checks include monitoring vibration and temperature rise in various areas; the temperatures should be within specified ranges (700 for motors, 750 for bearings, and 700 for reducers). The integrity of all components in the hydraulic system is also checked, as well as whether the system’s oil pressure is within the specified limits. Additionally, it is ensured that there is no vibration or abnormal noises in the pipes. Regularly inspect the cable reel mechanism: check whether the exterior of the cable reel is scratched, crushed, or broken, whether there is any jamming in the reel, and whether the rotation of the cable reel is synchronized with the movement. During coal loading and unloading operations, if large iron pieces, wooden pieces, stones, or large coal chunks (the four types of large objects) are detected, the machine must be stopped immediately for cleaning, to prevent damage to the conveyor belt or blockage of the coal discharge pipes. During operation, if a situation that endangers the safety of personnel and equipment is detected, the machine should be stopped immediately by pressing the emergency stop button. When the wind force reaches level 6, operations of the bucket wheel conveyor must be stopped. Take wind protection measures: clamp the rail clamps, park the cantilever frame facing the wind on top of the coal pile, and anchor it with an anchor. When operating in windy conditions, it is necessary to first check the brake and rail clamp systems of the bucket wheel loader. Drain all the water from the dust removal system before the temperature drops below 0°C. When the temperature is below 15°C, the heater must be turned on before operating the bucket wheel loader. The two bucket conveyors should have one in the stacking mode and the other in the unloading mode, with the switch being made twice a week. All lighting of the bucket wheel conveyor should be turned on at night. 290. What tasks should be carried out after the bucket wheel conveyor is shut down? Answer: 1) Check whether there are any dents or scratches on all rotating parts. Check the hydraulic system for oil leaks or other abnormalities. Check that all protective devices, limit switches, proximity switches, etc., are free from defects or malfunctions. Before leaving the machine, check whether the rail clamps and anchoring devices are properly clamped and anchored. Check whether the cable is in good condition. Check each cutting point for coal sticking; remove any stuck coal immediately. Clean the sanitary areas under the responsibility of this position. Contact the program-controlled duty officer to fill out the equipment defect form. Basic components and working principle of the dust collector: Answer: Basic components: The water bath type dust collector is mainly composed of a dust collector housing, air inlet pipe, water inlet pipe, air outlet pipe, water barrier plate, motor, fan, water inlet valve for cleaning, slurry discharge valve, water level detection device, overflow valve, etc. Working principle: The motor drives the fan to rotate, creating a negative pressure at the inlet of the fan. Under this negative pressure, a negative pressure is generated on the side containing clean air inside the housing, while the side with dusty gas has positive pressure. As a result of this pressure difference, irregular ripples are formed on the water surface. At the same time, a gap is formed between the dusty gas side and the clean air side. The dusty gas rapidly passes through the water surface and makes its first contact with it; the water absorbs the dust present in the dusty gas, simultaneously carrying away a large number of water droplets. These water droplets come into contact with the dusty gas on the clean air side, and once again the dust comes into contact with the water droplets. The dust is absorbed by the water droplets and continues to rise, only to be stopped by the water baffle and then return to the water surface. During the two contacts with water, the majority of the dust in the dusty gas is adsorbed by the water and settles in it; as a result, the dusty gas becomes cleaner and is discharged into the atmosphere by a fan. 291. What are the basic components and working principle of bag filters? Answer: This dust removal unit consists of an air intake chamber, a ash discharge chamber, a filtration chamber, a clean air chamber, a fan, and ash cleaning components. Working principle: When dust-laden gas enters the filtration chamber through the air inlet and passes through the filter bags from the outside inward, the dust is trapped on the outer surface of the filter bags. The clean air enters the bags and is then discharged into the atmosphere through the air outlet via an ejector and a clean air chamber. As the dust on the surface of the filter bags increases, causing the equipment resistance to rise to the set value, the differential pressure controller sends a signal. The controller then activates the blowing system, and compressed air is ejected through the outlet pipe. It enters the annular channel of the ejector tangentially via the insertion pipe, and is sprayed downward at the speed of sound within this annular space, creating a vacuum at the upper part of the ejector. Some of the air in the clean air chamber is drawn in as a secondary airflow. The compressed air together with this secondary airflow enters the filter bags, causing them to expand rapidly, which generates shock vibrations and creates an external airflow that blows away the dust adhering to the outside of the filter bags and between their fibers, thereby cleaning the filter bags. The cleaned dust falls to the ash discharge port and is removed; after the injection process is complete, the filter bags return to their filtering state. 292. What are the steps for local start/stop operation of a belt-type magnetizer? Answer: 1) Set the transfer switch “Programmed/Local” to the “Local” position. Open the door of the control cabinet and sequentially close the air switches QF1, QF2, QF3, and QF4. Start the belt first, then start the excitation. 4) Rotate the “adjustment knob” (clockwise to increase), gradually raising the current to 10–15A. 5) When shutting down, first stop the excitation, then stop the belt. 293. Basic components and working principle of the disc type iron remover: It consists of an excitation coil, a housing, a suspension device, a traveling mechanism, a locking device, and a control cabinet. Working principle: The magnetic field generated by an electromagnetic magnet remover is a non-uniform magnetic field. When ferromagnetic objects enter this non-uniform magnetic field, they experience different degrees of magnetization depending on their position; the strength of the magnetic field also varies. The end with a higher degree of magnetization experiences a greater force, while the opposite end experiences a smaller force. Therefore, the force exerted on an object in a non-uniform magnetic field is uneven; its resultant force is greater than 0, causing the object to move toward the side where the force is stronger. This is how ferromagnetic objects move in a directed manner within a magnetic field. After the iron remover has been in operation for a while, another iron remover moves to its working position and starts to function, while the current iron remover moves to the waste-iron disposal location to discard the iron. 294. Inspection before handover and startup of the sewage pump: Answer: 1) Check that the foot screws of the motor and pump body, as well as all the connection bolts, are tight and not loose. Check whether the motor’s wiring and grounding wires, as well as the protective cover, are in good condition. Check whether the automatic start-stop device of the sewage pump is functioning properly and whether the water level is at the normal level. The coupling connection bolts are intact, and the rotor rotates smoothly. There is no leakage of water or air from the pump body, the outlet pipe, or the inlet pipe. The sludge in the sump wells and coal settling tanks is in normal condition. 295. What is “four standards in one”? Answer: It is a comprehensive management system established within the framework of the ISO9001, ISO14001, OHSAS18001, and NOSA Five-Star safety, health, and environmental management systems. Based on the GB/T19001-2000 standard, it integrates the requirements of GB/T24001-2004, GB/T28001-2001, and CMB253 2004 management standards, thereby enabling integrated management of quality, environment, and occupational health and safety. 296. The policy of the company’s quality, safety, health, and environment management system is: people-oriented, a combination of prevention and control, safety and reliability, energy conservation and environmental protection, health and civilization, integrity and compliance, the pursuit of excellence, and spreading light. 297. What are hazard sources, hazard identification, risk, and risk assessment? Answer: Hazard source: A source or condition that may cause injury or occupational disease to persons, property damage, or impairment to the workplace environment, or a combination thereof. Hazard identification: The process of recognizing existing hazards and determining their characteristics. Risk: The combination of the likelihood of a specific hazardous event occurring and its consequences. Risk assessment: The entire process of evaluating the level of risk and determining whether it is acceptable. What does 298.5W1H mean? What–What to do? Why—why do this? When–When should it be done? Where – Where to do it? Who—who will do this work? How – What method should be used to do it? 299. What are the ‘four musts’ principles that are adhered to regarding issues of quality, safety, health, and environmental protection? Answer: Everything has a responsible person, everything follows established rules, everything is under supervision, and everything can be traced back to evidence. 300. Under what circumstances should braking devices be installed? Answer: When the inclination angle of a belt conveyor exceeds 40 degrees, a braking device is generally installed to prevent reverse rotation in the event of a shutdown under heavy load