500 Short-Answer Questions on Coal Transportation in Power Plants----(III)

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201. What damage can occur if a steel-ring type spiral cleaning idler does not rotate for an extended period of time? Answer: Worn belts reduce cleaning efficiency. In severe cases, it is possible to scratch or cut the belt ； The sticky coal gets caught in the drum or weight, causing the belt to deviate from its path. 202. The belt does not deviate from its path when it is 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) Deflected 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 iron removers, affecting 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 coupler, 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 an empty section cleaner, and where is it usually installed? Answer: It is used to remove material stuck on 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 provided, and the hydraulic coupling has a fuse-based overload protection. 209. What are the consequences of clogged screen 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 breaking 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 pre-startup inspections of 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 cloth 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 tearing 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 should 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 supervisors, 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 cleaning is required. 220. What are the limit protections available for 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, limits for rotation and movement within the 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 facilities. 222. Why is it required that the angle between the cantilever frame and the belt conveyor on the ground be less than 30° when the bucket wheel loader is moved quickly? Answer: To ensure the stability of shunting operations and prevent the bucket wheel 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 broken, whether there is any jamming in the reel, and whether the reel rotates smoothly and in sync with the movement. 224. Requirements for parking the bucket wheel loader. Answer: 1) Place the bucket wheel facing the wind on top of the coal pile; it is strictly prohibited to suspend it above the ground conveyor belt or with its arm hanging 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 conveyor in the 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 lose its effectiveness, 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 catch on the tracks or tip over. 227. What does the programmed duty operator use to select the system operation mode? Answer: Based on the operation of equipment in the coal transport system, its availability, the presence of equipment defects, coal quality requirements, the economic efficiency of the operating mode, and instructions 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 the components, prevent rust on 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 vapor 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 that allows on-site operators to stop the operation of the equipment at any time when they detect equipment failures or threats to personal 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 transmit 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 sieve with holes to sort materials according to 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 creating 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 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 particles 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 the particles are discharged through the openings in the screen. 241. What are the basic principles for setting up interlocks between various devices 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 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 control, the coal crusher can be started first and stopped last; otherwise, the proper operation 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 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 mill, 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 screen 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. Processing: 1) Tighten screws ； 2) Replace the impeller claws ； 3) Remove large 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 implemented in work related to work safety? Answer: When planning, arranging, checking, summarizing, and evaluating production, safety work is also planned, arranged, checked, summarized, and evaluated at the same time. 247. How to prevent electric shock accidents? Answer: 1) Strictly implement electrical safety regulations. 2) Carry out thorough electrical safety education and outreach efforts. 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 detected 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) If 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 clogs or it gets stuck by foreign objects, 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 indication 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 the various inspectors so as to carry out inspections and preparatory work before the system starts operating. 2) Check that the power connections for each component are correct, have 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 areas), 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 joint surfaces or shaft ends. 3) The foundation screws of the motor and reducer, as well as the connection bolts of each drive drum, are all tightened properly 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 stuck to the drum walls, nor any damage. 10) The coal plows are flexible and reliable when in the raised position. 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 piers 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 conveying system are in good condition, reliable, and functioning properly. 21) The dust collectors and iron removers 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 rises 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, the higher the volatile matter content, the faster the ignition speed and the lower the ignition temperature; as a result, the loss from incomplete combustion of the ash and the combustible content in the fly ash are reduced. Therefore, the volatile matter content of coal has a significant impact on the selection of boiler equipment design, the layout of heating surfaces, and 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, the combustion stability of the boiler is poor. 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. Increased wear on the heating surfaces also 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 fusion 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 transportation system: the impact of changes in calorific value on the coal transportation 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 load, and even lead to the shutdown of the furnace. 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 correspondingly. High moisture content during coal use reduces the efficiency of heat utilization and increases coal consumption. 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. When the moisture content in coal exceeds 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 transport 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 substances 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 on the coal conveyor belt? Answer: To ensure safe operation, all the equipment in the coal transport system is started and stopped in a specific sequence according to certain operational requirements, with one device regulating the operation of another. 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 stopped, it is shut down 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 come before it in the interlock sequence shut down automatically, while the devices that follow continue to operate. This helps to avoid or reduce 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 toward the discharge side. Solution: 1) Replace the plow blade or remove debris ； 2) Correcting plowshare ； 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) Offset adjustment. 261. What are the causes of belt breakage? How to handle it? Answer: Reasons: 1) Poor quality of the adhesive used 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 chutes ； 5) Remove coal accumulation at the head and tail to prevent blockages ； 6) Clear blockage ； 7) Reduce the transport 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 of it 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 the front end. 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 ensure that the distance between the sealing strip and the belt is at least 5 cm. Inspect the drive rollers and all direction-changing rollers for any hardware or debris inside them. Check all belts in the system (especially those behind the empty-section sweepers) for any debris. Verify that none of the idler rollers have misaligned shafts or missing dust covers. Also, check whether there is any debris trapped 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 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 situation that could lead to belt tearing is detected, the emergency stop button must be pressed immediately to shut down the equipment ； 2. During operation, it is strictly prohibited to operate the equipment beyond its capacity. If any abnormal objects or \"four large pieces\" are found on the belt, contact the programming operator promptly. In emergency situations, the emergency stop cable must be pulled immediately to shut down the machine ； 3. When the programmed duty officer receives a report of an abnormal situation from the inspector, they should closely monitor the operating 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 unattended, or engage in any activities unrelated to work while on duty ； 5. In addition to strictly adhering to operational safety measures, the bucket wheel crane 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 drop pipes ； 7. During operation, the programmed main and auxiliary duty officers 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 duty officer 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 should be contacted for resolution ； 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. Strict monitoring should be exercised for equipment with serious defects (belts that are severely worn and scratched) ； 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 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 specified 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 ensure there are no abnormalities before checking their temperature and vibration levels ； 266. Measures to prevent electrical fires in coal conveying 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 repair ； Upon discovering arcing at the cable connections on site, it is necessary to report to the team leader immediately and contact the relevant maintenance departments promptly for handling ； 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 wires, iron wires, 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 required 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 screens, safety measures must be taken; there must be at least one supervisor to prevent 3) the cleanup workers 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 wash water to splash onto the MCC cabinets and various local control boxes ； 2. After use, the door of the on-site MCC cabinet must be closed tightly ； 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 inspect the 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 cabinets 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 wires made of iron, copper, 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 feeding 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 avoid situations that could affect the load of the units ； 270. What are the main functions of coal conveying program 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 mixing methods 271. What is the activation mode for the interlock system of the coal conveying system? Answer: When programmatic interlock automatic control is used, the interlocks between devices are automatically activated. When manual control via program interlock is used, the interlock between devices is activated automatically. When manual control for unlocking is used. Interlock between devices is released. Unlocking for 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 (the 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 are consistent with 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 surveillance system is working properly. The equipment was put into trial operation; it started and stopped properly, and operated normally. The coal feeding mechanisms were intact (except for the equipment under maintenance), and all displays as well as electrical panels and cabinets 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 one sign to take over the shift. If problems arise after taking over, the person who took over shall be held responsible. Upon taking over, the coal level in the coal bins was checked; the inspections carried out on site showed that the coal levels were normal, all being above 8 meters, and all the coal shovels 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 sanitary areas under the responsibility of this position are kept clean, meeting 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 prior to system operation. 2. Check that the power connections for all components are correct, have 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 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 determined 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 tested motor and cable. Select the appropriate measuring tool and check that it is in good condition; also 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, redirecting drum, tensioning drum, sets of parallel idlers, sets of trough idlers, sets of buffer idlers, trough-type self-aligning idlers, parallel-type self-aligning idlers, tensioning devices, cleaners, empty-section cleaners, guide channels, frame, safety guards, protective covers at the head and tail ends, 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 displacement should be ≤2 mm. The temperature of the reduction gear 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 amount. 5) During operation, close attention should be paid to the condition of the belt at the outlet of the feed chute and at the point where coal is discharged from the conveyor belt. If abnormal coal discharge or 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 operating properly, the inspector shall report to the shift 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 operator determines the operating mode and frequency of the vibrators based on the quality of the coal. 9. The tensioning device is working properly; the weight should not reach its extreme position, the track should be smooth without any deformation, there should be no sticking in the ropes or wheels, and the steel wire rope should not have any short strands. 10. All protective devices should operate properly. 11. When a cut on the belt is detected, stop the machine immediately by pulling the emergency stop cord, and report to the team 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 spray device at the outlet of the material guide chute promptly. The water spray volume must not be too high, to avoid affecting 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 adhering to 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, and other debris from beneath the belt conveyor. 16. It is strictly prohibited to cross the belt at any time; if it is necessary to pass over it, a walkway bridge must be used. 17. When the sealed leather strip comes out, it must not be adjusted by a single person. 18. It is strictly prohibited to use belt conveyors as other means of transportation. 19. It is strictly prohibited to start the belt conveyor under heavy load. 20. In case of the following situations, the emergency stop switch should be activated immediately to shut down the machine. (1) The motor overheats and starts smoking. (2) There are phenomena that pose a threat to personal safety. (3) Blockage of the coal dropping pipe. (4) Scratches or tears in the belt. (5) A fire breaks out in the system (e.g., the belt catches fire, electrical equipment catches fire, 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 dealing with 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, economical, 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 cannot operate, it is necessary to report to the shift supervisor as well as the company’s and department’s on-duty managers first, and actively work to restore system operation to ensure a supply of coal for the boiler. Any equipment malfunctions or potential hazards discovered should be promptly reported to the shift supervisor and the PLC operator, so that the cause of the malfunction can be identified as soon as possible. Enter equipment defects into the MIS promptly and contact the maintenance department to address 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 rectified. Equipment that must operate despite having defects should have appropriate safety measures put in place depending 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 go of any aspect.\" 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 in sequence, starting from the bin with the lowest coal level (except for the maintenance bin), moving upward. The programmed duty operator then manually activates another belt conveyor in the coal bin using programmed interlocking, and by clicking on the “Programmed Allocation” system, the coal is allocated to the bins in order, starting with the lower ones 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 detecting 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 impact forces in order to break up coal lumps. When these coal lumps enter the 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. Hard-to-break 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. If a blockage is detected, stop the machine immediately; it can be restarted only after the cause has been identified. 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 wash 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 cleaning, maintenance, or other tasks 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 composition: 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 electric control box controls the rotation of the motor; through a reducer and a drive shaft, the impeller inserted into the gap of the coal unloading chute is made to rotate, which in turn causes the leaf claws to move rotatably and push the coal out of the chute. The coal then falls onto the belt conveyor below via the 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 get close to each other, their travel switches or proximity switches activate, causing the impeller coal feeder to move in the opposite direction automatically. The speed of the impeller is controlled by an inverter, which enables the coal feeding amount supplied by 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 programmed 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. To change the direction of movement, it is necessary to first stop the operation of the moving system, then press the button for the opposite direction, and the device will change its direction of movement. 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 start the impeller coal-shifting mechanism when the lower belt conveyor is not operating properly. It is strictly prohibited to stop the impeller coal feeder without 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 maintain 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 by having 10 parallel screening rollers rotate in the same direction. When the material to be screened (coal) falls onto the first three rollers on the screen surface (the inclination angle of the first six rollers gradually changes from 150° to 0°, while the last four rollers maintain a 30° angle), the material spreads out quickly and is propelled forward by the rotating rollers and screening blades. Meanwhile, particles smaller than the size of the screen openings fall through those openings due to their own weight and the rotational force exerted by the blades. Particles larger than the openings move along the screen surface toward the outlet of the roller screen, where they are fed into a 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, a communication cable reel mechanism, 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 bucket turns downward, it scoops coal into the bucket; when the bucket wheel continues to rotate to its highest position, the coal falls due to its own weight, and the arc-shaped coal guide plate directs the coal toward the receiving chute, from where it is transported to the central coal discharge pipe by a cantilevered belt conveyor. 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 transmission system, thereby completing the coal retrieval process by the bucket wheel conveyor. When stacking is required, the tail car is raised to the upper part of the boom conveyor. The coal fed into the system travels via the ground conveyor and the tail car conveyor before falling onto the boom conveyor. The conveyor then reverses direction, transporting the coal to its head end where it drops into the stockpile, 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 duty operator before stacking or taking coal. It is strictly prohibited to consume alcohol within 8 hours before operating the bucket wheel loader at work. It is strictly prohibited to move the heavy vehicle without activating the sound 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 large vehicle, the cantilever frame must be positioned at an angle of less than 300 degrees 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 hauler is in motion. It is strictly prohibited for the bucket wheel conveyor to operate under overload conditions. 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 function smoothly and reliably before proceeding with the operation. When electrical or mechanical faults such as those in motors or reducers are detected, the machine must be stopped for repairs 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 tightness 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 drum mechanism. Check whether the surface of the cable drum shows any scratches, dents, or cracks; whether there is any jamming in the drum; and whether the rotation of the cable drum is synchronized with the movement of the equipment. During coal loading and unloading operations, when larger pieces of iron, wood, stone, or large coal blocks (the four types of large debris) are detected, the machine must be stopped immediately for cleanup 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, position the cantilever frame on top of the coal pile facing the wind, 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 wheel conveyors should have one in loading mode and the other in unloading mode, with the roles switched twice a week. All lighting of the bucket wheel conveyor should be turned on at night. 290. What tasks should be performed after shutting down the stacker-reclaimer? Answer: 1) Check whether there are any bruises or scratches on all rotating parts. Check the hydraulic system for oil leaks or other abnormalities. Check whether there are any defects or malfunctions in various protective devices, limit switches, proximity switches, etc. Before leaving the machine, check whether the rail clamps and anchoring devices are securely clamped and anchored. Check whether the cable is in good condition. Check each blanking point for coal sticking; remove it immediately if any is present. Clean the sanitary areas under the responsibility of this position. Contact the programming operator to fill out the equipment defect form. Basic components and working principle of dust collectors: Basic components: A water-bath dust collector mainly consists of a dust collector housing, air inlet pipe, water inlet pipe, air outlet pipe, water shield baffle, motor, fan, water inlet pipe, servo-controlled water inlet valve, sludge 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 numerous 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 before being stopped by the water baffle and returning 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 a bag filter? Answer: This dust removal unit consists of components such as an inlet chamber, ash discharge chamber, filtration chamber, clean gas chamber, fan, and ash cleaning system. Working principle: When dust-containing 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, creating a vacuum at the upper part of the ejector. Some of the air in the clean air chamber is drawn in (referred to as 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, thus cleaning the filter bags. The cleaned dust falls to the ash discharge port and is removed; after the spraying is completed, the filter bags return to their filtering state. 292. What are the steps for local start/stop operation of a belt-type iron remover? Answer: 1) Set the changeover 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, stop the excitation first, and 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 mechanism, 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 greater 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 working, while the current iron remover moves to the waste-iron discharge position 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 with no signs of looseness. 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 are no leaks of water or air in the pump body, discharge pipe, and suction 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 environment 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 achieving 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 diseases to people, property damage, or issues related to the workplace environment, or a combination of these. 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