Equipment Technical Question Bank (with Answers)

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Question bank for the technical theory exam: I. Fill-in-the-blank questions. (Total 60 questions) 1. A directional control valve utilizes the relative motion between the spool and the valve body to change the direction of oil flow, thereby opening or closing the oil circuit. 2. Common sealing elements include: (O-ring), Y-ring, V-ring, etc. 3. The greater the viscosity of engine oil, the poorer its flowability; the lower the viscosity, the better the fluidity, but its (lubricating properties) deteriorate. 4. The lubricity of lubricating oil changes with temperature; when the temperature is too high, the adsorbed film decomposes and is destroyed. 5. Dynamic sealing refers to a type of sealing in which there is (relative motion) between the sealing surface and the mating parts. 6. Helical and spur cylindrical gear transmissions have a higher load-carrying capacity, but they generate (axial thrust). 7. Based on the shape of their axis, shafts can be divided into two main categories: crankshafts and straight shafts. 8. The power transmitted by a V-belt is transferred through friction; therefore, the greater the tension of a belt of the same specification, the greater the power that can be transmitted. However, excessive tension can cause excessive forces on the components and lead to faster belt wear. 9. Rigid couplings can be classified into (fixed) and removable types based on their structural characteristics. 10. (Static seal) refers to a seal in which there is no relative movement between the sealing surface and the mating parts. 11. (Dynamic seal) refers to a seal in which there is relative motion between the sealing surface and the mating parts. 12. The hydraulic losses of centrifugal pumps include impact loss, vortex loss, and (friction loss along the flow path). 13. Excessive clearance in rolling bearings can cause load concentration, resulting in shocks and vibrations, as well as severe friction, wear, and heating. 14. The hazards that can occur when a centrifugal pump operates at a low flow rate for an extended period of time include: an increase in the pump’s temperature, an increase in radial thrust, and the occurrence of cavitation. 15. When starting a centrifugal pump, the inlet valve should be opened first, followed by the (outlet valve). 16. The maximum axial movement of one ring of a rolling bearing while the other ring is fixed is called (axial clearance). 17. The dynamic balance of the rotor is achieved by adding or removing weight, so that the amplitude of vibrations when the rotor rotates at its operating speed remains within acceptable limits. 18. Rotor mass imbalance is one of the main causes of machine vibration. The method of static balancing of a rotor involves reducing or increasing the weight on one side or the opposite side of the imbalanced mass, so that the rotor can remain stationary in any position. 19. The basic performance parameters of commonly used centrifugal pumps include (flow rate), head, power, rotational speed, etc. 20. When it is necessary to adjust the flow rate in the pipeline of a centrifugal pump, and given the fixed conditions of the equipment, it is common to adjust the outlet valve of the pump; the inlet valve of the pump should not be adjusted to reduce the flow rate, as this may lead to cavitation. 21. After the rolling bearing is assembled, the inner ring of the bearing will expand while the outer ring will (shrink); therefore, the assembly clearance should be smaller than the original value. 22. The function of the direction control valve is to control the flow direction of the oil in the hydraulic system, thereby changing the (movement direction) of the actuator. 23. Depending on the movement mode of the spool, directional control valves can be divided into slide valve type and (rotary valve type). 24. The installation of couplings requires that the (concentricity) of the two shaft axes be within a certain error range. Excessive deviation will impose excessive additional loads on the coupling, shafts, and bearings, resulting in heating, accelerated wear, and even fatigue fracture. 25. The two parameters used to measure coupling deviation are (axis offset) and axis skew. 26. The main failure modes of parts are wear, (deformation), fracture, and erosion. 27. Compression equipment is generally divided into five systems: the drive system, the compression system, the cooling system, the lubrication system, and the conveying system. 28. Piston compressors can be classified by the number of stages into single-stage and (multi-stage) compressors. 29. The glass plate level gauge operates on the principle of a (communicating vessel). 30. Rolling bearings should have the necessary clearance to compensate for (manufacturing and assembly) deviations and thermal expansion, allowing an oil film to form and ensuring smooth and flexible motion; otherwise, seizure may occur. 31. Under a certain load, the total number of revolutions experienced by any rolling element in the bearing or by the raceways of the inner and outer rings before fatigue pitting occurs, or the number of operating hours at a certain speed, is referred to as the bearing’s lifespan. 32. Sealing ring cooling can promptly dissipate the (friction heat) of the mechanical seal. 33. The slide valve consists of a valve body section, a (transmission section), and a control section. 34. Based on their working principle, compressors can be divided into two main categories: speed-type and (volume-type). 35. Positive-displacement compressors reduce the volume by means of a piston that moves (back and forth) or rotates inside the cylinder, thereby increasing the gas pressure. 36. A piston compressor relies on the reciprocating motion of the piston within the cylinder, in combination with the corresponding opening and closing actions of the air valves, to enable the gas inside the cylinder to go through four processes: expansion, intake, compression, and exhaust. 37. The critical speed of a rotor mainly depends on the rotor’s (mass) and stiffness. 38. The main parameters of a centrifugal compressor include (flow rate), outlet pressure or pressure ratio, power, efficiency, speed, critical speed, and energy head. 39. The thermodynamic processes of centrifugal compressors include (isothermal compression process), adiabatic isentropic compression process, and polytropic compression process. 40. There are many types of agitators; the commonly used ones include turbine type, (impeller type), anchor type, and frame type. 41. Stirrers typically use methods such as installing baffles or guide cylinders to enhance the mechanical stirring effect. 42. Chain drives are mainly used in situations where an accurate gear ratio is required, when the two shafts are far apart and gear drives are not suitable, as well as in other cases where gear drives cannot be employed. 43. When a skeletal rubber seal is used to prevent oil leakage, its sealing lip should face the bearing; when it is used to prevent the ingress of external contaminants, its sealing lip should face away from the bearing. 44. Reducers can be classified according to the type of transmission as: (gears), worm gears, planetary gears, and planetary cycloidal pin gears. 45. In belt drives, the wrap angle of the belt around the pulleys must not be too small; for V-belts, this angle should not be less than (120°), otherwise slipping is likely to occur. 46. Cylindrical gear reducers can be classified according to their transmission layout into: open-type, split-type, and shaft-connected type. 47. The operating speed of rotating machinery should not be equal to or close to the critical speed, otherwise it will cause resonance in the rotor, leading to serious consequences. 48. The adjustment of the tightness of a triangular belt is mainly achieved by changing the distance between the two shafts or by adjusting the tension. 49. The lubricating oil film in sliding bearings has vibration-damping capabilities, allowing them to withstand large (impact) loads. 50. Stirrers for low-viscosity fluids generally operate in turbulent conditions, and they can also be divided into two types: axial flow type and radial flow type. 51. The function of a hydraulic oil pump is to convert mechanical energy into (hydraulic) energy, while cylinders and pistons transform the pressure energy of the oil into mechanical energy for the movement of the mechanism. 52. Bearings are generally divided into two main categories: (sliding bearings) and rolling bearings. 53. In mechanical seals, if the specific pressure on the end faces caused by the high-pressure medium exceeds its acceptable range, it will lead to the breakdown of the fluid film, resulting in seal failure. 54. Viscosity is a parameter used to evaluate the fluidity of oils. 55. The common lubricants used for equipment lubrication are (lubricating oil) and grease. 56. A gear pump transports liquid by utilizing the changes in working volume that occur during the process of gear meshing. 57. Under normal circumstances, the (impellers) of a multi-stage pump are installed symmetrically to eliminate axial forces. 58. The bearings of a centrifugal pump are the components that support the rotor, while also bearing axial loads. 59. After wear and tear, the (clearance) of bearings increases, and their precision decreases. 60. When rolling bearings are in operation, fatigue (pitting) may occur on the varying contact surfaces between the rolling elements and the rings. II. True or False questions. (Total of 40 questions) 1. When the agitator rotates, the impeller exerts two main effects on the fluid: one is shearing the fluid, and the other is promoting its circulatory flow. (√) 2. Mechanical natural wear is the gradual wear of a metal surface that occurs under normal operating conditions. (√) 3. If the adsorption force between the oil film and the interface is strong, and the boundary film does not easily break, then the lubricant has poor quality. (×) 4. Viscosity is a key factor in selecting lubricants; lubricants with high viscosity have poor fluidity, can handle only low loads, and it is difficult for them to form an oil film. (×) 5. The smaller the surface roughness of the two relatively sliding surfaces in a sliding bearing, the higher the machining precision, and the easier it is to achieve fluid friction. (×) 6. The service life of a rolling bearing refers to the time it can operate properly under a certain working load, or the number of revolutions it can make while operating normally. (√) 7. Viscosity has a significant impact on the flow rate and pressure drop during fluid flow and transportation. (√) 8. The lubrication oil level of the pump should be maintained within the range of 1/3 to 1/2. (×) 9. A blocked oil inlet pipeline in the oil pump will cause the oil pump’s temperature to rise. (√) 10. When cavitation occurs in the pump, the outlet valve can be opened wider to eliminate it. (×) 11. Do not fill the centrifugal pump with liquid before starting it. (×)12. The ability of the active molecules in lubricants to form a high-pressure-resistant chemical reaction film on the friction surfaces is known as extreme pressure property. The better the extreme pressure property, the stronger the capacity to resist high pressures from destroying the oil film. (√) 13. According to the performance curve of centrifugal pumps, as the flow rate increases, the head also increases. (×) 14. The torque-transmitting capability of gear couplings is superior to that of other couplings. (√) 15. Hydraulic transmission enables stepless speed control over a wide range in a convenient manner. (√) 16. At present, it is not possible to choose a too high pressure for the hydraulic system, and the main reason is that the sealing technology does not meet the required standards. (√) 17. Mechanical natural wear is the gradual wear of a metal surface that occurs under normal operating conditions. (√) 18. Sleeve bearings can operate at high speeds and can withstand significant impact and vibration loads. (√) 19. If there is air in the hydraulic system, the hydraulic actuator may experience crawling motion. (√) 20. Before starting to introduce steam, check the status of all valves in the process flow, and isolate the steam pipeline from other parts of the process to prevent steam from entering those pipelines during steam introduction. (√) 21. Rigid couplings are prone to shock and vibration when the load changes significantly. (√) 22. In both ordinary flat keys and wedge keys, the working surfaces are the sides of the key; during operation, motion and torque are transmitted through the compression between the key and the sides of the keyway. (×) 23. Under high-speed and heavy-load conditions, the local contact areas of gears experience high temperatures that cause softening or melting; as a result, the gears stick together. The softened tooth surfaces are then torn away, forming adhesion grooves. In gear drives under heavy loads, the pressure on the tooth surfaces is very high, making it difficult for an oil film to form, or oil deficiency can also lead to adhesion. (√) 24. Components with uneven mass distribution generate inertial forces and moments during rotation, which result in additional forces. These additional forces have a significant impact on high-speed, heavy-duty, and precision mechanisms. (√) 25. To prevent surging, a flow return valve is primarily used to control the compressor’s flow rate. (√) 26. The disadvantage of the cross-slider coupling is that at high rotational speeds, the eccentricity of the intermediate disc results in significant eccentric inertial forces, which impose additional loads on the shafts and bearings. (√) 27. Changing the pump’s speed actually means changing its characteristic curve. (√) 28. Under high-speed and heavy-load conditions, the local contact areas of gears can become softened or even melted due to high temperatures, causing the gears to stick to each other. The softened tooth surfaces get torn off, resulting in scuffing marks. In gear transmissions subjected to heavy loads, the pressure on the tooth surfaces is very high; as a result, an oil film fails to form, or there may be insufficient lubrication, both of which can also lead to scuffing. (√) 29. Pressurized filters can be classified into plate and frame filter presses, chamber filter presses, pressurized liquid filter presses, drum filters, etc. (√) 30. The solidification of lubricating oil is caused by the presence of paraffin in the oil; at low temperatures, paraffin crystallizes out. (√) 31. The spring-type safety valve is the only type of safety valve. (×) 32. Flow rate is divided into volumetric flow rate and mass flow rate. (√) 33. The solubility of gases in a solution increases as pressure rises and decreases as temperature increases. (√) 34. For impellers with balance holes, generally speaking, the closer the balance holes are to the seal ring, the better the balancing effect. (√) 35. When a single-suction pump is in operation, axial thrust is inevitably generated. The direction of this thrust is the same as the direction of water inflow; it points from the inlet toward the impeller. (×) 36. When components with uneven mass distribution rotate, inertial forces and inertial moments are generated, which result in additional forces. These additional forces have a significant impact on high-speed, heavy-duty, and precision mechanisms. (√) 37. Based on the corresponding position of the gear shaft, reducers can be classified into horizontal and vertical types. (√) 38. The failure modes of belt drives include slippage and fatigue failure. (√) 39. The control operation modes of pressure filter machines can be divided into batch and continuous types. (√) 40. The radial bearings of centrifugal compressors use tilting-pad bearings, which can eliminate oil film oscillations. (√) III. Multiple-choice questions. (100 questions in total) 1. Reducing the flow rate of a centrifugal pump (B) will affect the pump’s cavitation performance, leading to cavitation occurring. A. Outlet valve ； B. Inlet valve ； C. Connecting valve 2: In accordance with the standards for functional pumps, a centrifugal pump should achieve (　C　) of its nameplate capacity. A: 70% B: 80% C: 90% 3. The temperature of rolling bearings should not exceed (B). A: 65℃　　B: 70℃　　C: 75℃　　D: 80℃ 4. When starting a metering pump, it is better to set the stroke to (　A　). A: 0% B: 10% C: 50% D: 100% 5. The purpose of turning the standby pump is (A). A. Preventing the shaft from bending B. Preventing the shaft from getting stuck C. Preventing poor lubrication. 6. \"Shaft seizure\" is mainly caused by wear of (B). A abrasive wear ； B-glue wear ； C Pitting corrosion wear 7. The head of a pump refers to the (B) provided by the pump per unit weight of liquid. A. Energy B. Effective energy 8. The power of a pump refers to the (B) provided by the motor to the pump per unit of time. A. Energy ； B. The effective energy is 9. The temperature of the pump’s bearing housing should not exceed (A). A. 65°C B. 70°C C. 80°C. 10. After the pump starts, it is not allowed to use (A) to adjust the flow rate, in order to prevent the pump from experiencing vacuum conditions. A. Pump inlet B. Pump outlet 11. The function of the power part in hydraulic transmission is to convert mechanical energy into the (C) of the liquid. A. Thermal energy B. Electrical energy C. Pressure potential energy 12. The viscosity of lubricating oil indicates its flow properties and thickness; lubricating oil with high viscosity can withstand greater loads (A). A. Poor flow properties B. Good flow properties 13. Practice has shown that helical cylindrical gear transmissions are more stable and have greater load-bearing capacity compared to straight cylindrical gear transmissions. The main reason for this is the (C) of helical gears, along with the larger number of teeth in contact at any given time. A. Higher material strength B. Lower load-sharing coefficient than straight gears C. Higher load-sharing coefficient than straight gears 14. Key connections are mainly used to connect shafts and components mounted on them, providing circumferential fixation and (B). A. Positioning B. Transmitting torque C. Combining them into one unit 15. The pump’s suction height refers to the difference in height between the horizontal plane passing through the pump axis and (C). When this horizontal plane rises above the maximum suction height, the pump can no longer draw in liquid. A. Pump discharge port B. Pump body outlet C. Suction level 16. During pump operation, the uneven pressures on the outer surfaces of the impeller’s front and rear sections, along with the axial component of the hydrodynamic pressure on the inner surface of the impeller, create an axial force directed towards (B). A. Discharge port B. Suction port 17. Bearings that use the rotational motion of the shaft journal to bring oil between the friction surfaces, thereby creating a pressure oil film that separates these surfaces, are known as (B). A. Hydrostatic bearings B. Hydrodynamic bearings 18. Bearings that use lubricating oil under sufficient pressure to balance external loads and separate the friction surfaces, thereby enabling liquid friction, are known as (A). A. Hydrostatic bearings B. Hydrodynamic bearings 19. When the outlet valve of a centrifugal pump is opened or closed, (B). A. The pump’s performance curve changes ； B. The pipeline characteristics were changed, thus altering the shaft power ； C. The efficiency of the pump remains essentially unchanged. 20. During operation, a centrifugal pump generates not only axial force but also (B). A. Lateral force B. Radial force C. Centrifugal force D. Centripetal force. 21. The total amount of fluid that passes through any cross-section of a pipeline per unit of time is called (C). A. Flow velocity B. Head C. Flow rate D. Pressure. 22. The function of the working part in hydraulic transmission is to convert hydraulic potential energy into (A). A. Mechanical energy B. Nuclear energy C. Light energy. 23. (B) is the pressure control valve used to regulate system pressure and prevent overloading of the system. A. Rotary cylinder B. Relief valve C. Directional control valve. 24. Centrifugal pumps belong to (C). A Reciprocating pump B Positive-displacement pump C Vane pump. 25. The flow control valve operates by changing (C) in order to regulate the flow rate of the fluid through the valve, thereby causing the actuator to move at a corresponding speed. A. The pressure of the liquid B. The velocity of the liquid C. The size of the opening in the channel. 26. When one ring of a rolling bearing is fixed, the maximum radial movement of the other ring is referred to as (B). A. Radial displacement B. Radial play C. Axial play. 27. During use, the rollers and raceways in bearings wear out; when the wear reaches a certain level, the rolling bearing will (C) and become unusable. A. Overheat B. Get stuck C. Operate unevenly. 28. The characteristics of a screw pump are (B). A. Poor self-priming ability, low efficiency, and relatively quiet operation ； Model B has good self-priming capability, high efficiency, and produces low noise during operation ； C has poor self-priming ability, high efficiency, and produces loud noise during operation ； D has good self-priming ability, low efficiency, and produces loud noise during operation. 29. The shaft power of a pump generally increases as the flow rate increases (A). A. Increases B. Remains unchanged C. Decreases. 30. A rack can be considered as a gear of (B) type. A. Not a gear B. With an infinitely large diameter. 31. Different materials have different thermal conductivity values; generally, those with (D) have the lowest thermal conductivity. A Metal B Non-metal C Liquid D Gas 32. The purpose of operating centrifugal pumps in parallel is to achieve a larger (C) at the same head. A Energy B Efficiency C Flow rate D Shaft power. 33. Before starting a centrifugal pump, it is necessary to (B). A Open the outlet valve B Fill the pump with liquid C Fill it with lubricating oil D Turn off the power. 34. The impeller of a centrifugal pump is generally of type (B). A Open-type B Closed-type C Semi-open-type. 35. Lubricating oil has many functions, including the function of (A). A. Lubrication B. Sealing C. Improvement in the pump’s quality. 36. When the unit operates at its critical speed, (C) occurs; prolonged operation can lead to damage to the unit. A. Over-temperature B. Over-pressure C. Severe vibration 37. Based on the duration of wear, it can be classified as (B). A. Abrasive wear, adhesive wear B. Natural wear, accidental wear C. Fatigue wear, corrosion wear D. Abrasive wear, accidental wear 38. The appropriate temperature of the oil in the hydraulic system’s tank is generally within the range of (B). A. 40–50°C B. 55–65°C C. 65–75°C 39. The accumulator in a hydraulic system is a device used to store and release (A). A. Liquid pressure energy B. Liquid thermal energy C. Electrical energy 40. When starting up cooling equipment, (C) should be done: A. First introduce the hot material, then the cold material B. Introduce both simultaneously C. First introduce the cold material, then the hot material 41. During a hydrostatic test of a pressure vessel, the holding time at the test pressure should be (C). A. 10 minutes B. 15 minutes C. 30 minutes D. 60 minutes 42. The function of the water line on the flat flange sealing surface is (C). A. Fixed gasket, to facilitate installation; B. To protect the seal from damage; C. To improve sealing performance; D. No effect. 43. Under normal circumstances, the most commonly used type of head in pressure vessels is (B). A. Hemispherical B. Elliptical C. Disc-shaped D. Sphere without seams 44. Theoretically, within the same compression range, the work required for isothermal compression in a piston compressor is (A). A. Minimum B. Maximum 45. Theoretically, within the same compression range, the work required for adiabatic compression in a piston compressor is (B). A. Minimum B. Maximum 46. To adjust the clearance of the thrust bearing, it can be done by thickening or thinning the (A) shims. A. Non-working side B. Working side C. Both sides 47. For the thrust bearings, only (A) may be used as adjustment shims on the working and non-working sides, and the thickness must be uniform throughout the entire circumference. A. 1 piece B. 2 pieces C. 3 pieces D. Any 48. Among the 4 types of labyrinth seals used in centrifugal compressors, the one with the best sealing performance is (C). A. Smooth type B. Stepped type C. Honeycomb type D. Twisted type 49. The rotor has a certain protruding section at each bearing end, and the length of this protruding section has a significant impact on the rotor’s second-order critical speed, causing it to increase substantially (A). A. Decrease B. Increase C. Neither decrease nor increase. 50. Usually, oil film damping (B) the critical speed of the shaft, and it also (B) the resonance amplitude. A. Increase, increase B. Increase, decrease C. Decrease, increase D. Decrease, decrease 51. The advantage of radial tilting bearings is that each bearing pad can move freely, allowing for the formation of an optimal oil wedge under any conditions; they offer good stability at high speeds and are less prone to oil film oscillations. They are commonly used in (A) industrial steam turbines. A. High speed, light load B. High speed, heavy load C. Low speed, light load D. Low speed, heavy load 52. For rigid rotors, low-speed dynamic balancing is sufficient; the balancing speed is generally chosen to be the first-order critical speed (C). A. 40% B. 40%—50% C. Below 40% 53. When calculating the compression ratio of a compressor, both the discharge pressure and the suction pressure must be used (B). A. Gauge pressure B. Absolute pressure C. Both gauge pressure and absolute pressure 54. In a centrifugal compressor, the requirement for the contact surface of the radial bearing shells is (D). A. ≥50% B. ≥60% C. ≥75% D. ≥85% 55. The assembled gas valve is subjected to a airtightness test using kerosene; discontinuous droplet-like leaks are allowed in (C). A. Within 3 minutes B. Within 10 minutes C. Within 5 minutes D. Within 15 minutes 56. Generally, the larger the capacity of the pipeline network, the greater the surge amplitude (B), and the higher the frequency (B). A. Large ； High B. Large ； Low C. Small ； High D. Low ； At 57 below, the general pipe network capacity is low; thus, the surge amplitude is (A) and the frequency is (A). A. Small ； High B. Low ； Low C. Large ； High D. Large ； 58. In condition monitoring, the fundamental frequency refers to the frequency that is related to the rotational speed (A) of the rotor in a rotating machine. A. Equal B. 2 times C. 3 times 59. Currently, centrifugal compressors generally use (B) impellers. A. Forward bend type B. Rearward bend type C. Radial type 60. When the high-temperature butterfly valve is in the fully open position, the emergency shutdown time when the solenoid valve is activated should be (A). A. Less than 15 seconds B. Equal to 15 seconds C. More than 15 seconds. 61. The surfaces of the partition in a centrifugal compressor should be tightly fitted, with the maximum gap not exceeding (C). A. 0.05mm B. 0.15mm C. 0.10mm 62. Worm gears are used for transmission between two (C) shafts. A Parallel B Intersecting C Crossing 63. Under certain conditions of the system, the flow velocity in areas with a larger cross-section is (B) A High B Low C Unchanged 64. There are two ways for the flushing fluid to enter the sealed chamber: (C) A Radially and axially B Radially and tangentially C At a single point or at multiple points D In the forward direction and in the reverse direction 65. When using a belt drive, the wrap angle of the belt around the pulley must not be less than (D). A 135o B 130o C 125o D 120o. 66. Stirrers used for viscous fluids generally operate in a turbulent flow regime, and the ratio of the impeller diameter d to the tank diameter D lies within the range of (A). A 0.3-0.6 B1-2 C 0.5-0.9 D 0.9-0.98 67. Which of the following is not part of an axial flow fan? (C) A. Air collector B. Impeller C. Volute D. Diffuser 68. When performing a low-speed static balance test on the impeller of a centrifugal fan, the mass deviation at a speed of 1500 r/min or less should be no more than (A) A. 10g B. 8g C. 6g D. 5g 69. Mechanical transmission makes use of mechanical components such as pulleys, shafts, and gears to achieve (A) of energy A. Transmission B. Conversion C. Delivery D. Exchange 70. Which of the following is not a cause of high bearing temperature in centrifugal blowers? (D) A. Excessive grease B. Scorch marks on the bearings C. Poor alignment D. Leaks in the system 71. Classified by structure, which of the following does not belong to the turbine type? (D) A. Centrifugal B. Axial flow C. Mixed flow D. Positive displacement 72. Classified by structure, which type of fan belongs to the positive displacement category? (D) A. Centrifugal B. Axial flow C. Mixed flow D. Reciprocating 73. Based on the principle of separation, centrifuges can be divided into three types; which of the following is not one of them? (C) A. Centrifugal filtration B. Centrifugal sedimentation C. Centrifugal washing D. Centrifugal separation 74. Which method is used to separate materials with a high solid content and large solid particle sizes in a suspension? (A) A. Centrifugal filtration B. Centrifugal sedimentation C. Centrifugal separation D. Centrifugal washing 75. Which method is used to separate materials with a low solid content, small solid particle sizes, and a large difference in specific gravity between the solid and liquid phases? (B) A. Centrifugal filtration B. Centrifugal sedimentation C. Centrifugal separation D. Centrifugal washing 76. Which method is used to separate emulsions composed of two liquids with different specific gravities that are immiscible with each other, or to clarify suspensions with a low solid content and very small solid particles? (C) A Centrifugal filtration B Centrifugal sedimentation C Centrifugal separation D Centrifugal washing 77. The transmission ratio i of a certain transmission mechanism