Source: Thermal Power Plant Technology Alliance
1. What is a pump?
Answer: A pump is a kind of machinery that converts the mechanical energy of the prime mover into pumping liquid energy.
2. What is power?
Answer: The work done per unit of time is called power.
3. What is effective power?
In addition to the energy loss and consumption of the machinery itself, the actual power of the liquid is obtained by the pump per unit time, which is called the effective power.
4. What is shaft power?
Answer: The power transmitted by the motor to the pump shaft is called shaft power
5. Why is the power transmitted by the motor to the pump always greater than the effective power of the pump?
Answer: 1) When the centrifugal pump is running, a part of the high-pressure liquid in the pump will flow back to the inlet of the pump, or even leak out of the pump, so that a part of the energy must be lost;
2) When the liquid flows through the impeller and pump casing, the change of flow direction and velocity, as well as the mutual impact between fluids, also consume a part of the energy;
3) The mechanical friction between the pump shaft and the bearing and the shaft seal also consumes a part of the energy, so the power transmitted by the motor to the shaft is always greater than the effective power of the shaft.
6. What is the total efficiency of the pump?
Answer: The ratio of the effective power of the pump to the shaft power is the total efficiency of the pump.
7. What is the flow rate of a pump and what symbols are used?
Flow is the amount (volume or mass) of liquid that flows through a section of a pipe per unit of time. The flow rate of the pump is indicated by "Q".
8. What is the head of the pump and what symbol is it used for?
Answer: Head refers to the increment of energy gained by a fluid per unit weight. The head of the pump is indicated by "H".
9. What are the characteristics of chemical pumps?
Answer: 1) It can adapt to the requirements of chemical technology, 2) It is corrosion resistant, 3) It is resistant to high temperature and low temperature, 4) It is wear-resistant and erosion-resistant, 5) It is reliable in operation, 6) It has no leakage or less leakage, 7) It can transport liquid in a critical state, and 8) It has anti-cavitation performance
10. How many categories are commonly used mechanical pumps according to their working principles?
A: 1) Vane pump. When the pump shaft rotates, various impeller blades are driven to deliver liquid to pipelines or containers with centrifugal force or axial force, such as centrifugal pumps, vortex pumps, mixed-flow pumps, and axial flow pumps.
2) Positive displacement pumps. Pumps that use the continuous change of the volume of the pump cylinder to transport liquids, such as reciprocating pumps, piston pumps, gear pumps, and screw pumps;
3) Other types of pumps. For example, electromagnetic pumps that use electromagnetic to transport liquid electrical conductors, and pumps that use fluid energy to transport liquids, such as jet pumps, air boosters, etc
11. What aspects should be treated before the chemical pump is overhauled?
Answer: 1) Before the maintenance of machinery and equipment, it must be stopped, cooled, depressurized, and cut off the power supply;
2) Machines and equipment with flammable, explosive, toxic and corrosive media must be cleaned, neutralized and replaced before inspection and inspection before construction;
3) To overhaul flammable, explosive, toxic, corrosive media or steam equipment, machines and pipelines, the material exit and inlet valves must be cut off, and blind plates must be added.
12. What process conditions should be met before the chemical pump is overhauled?
A: 1) Stop, 2) Cooling, 3) Pressure relief, 4) Power cut-off, 5) Replacement
13. What are the general principles of mechanical disassembly?
Answer: Under normal circumstances, it should be disassembled first outside and then inside, first up and then down, and the whole parts should be disassembled as a whole as much as possible.
14. What are the causes of power loss in the centrifugal pump?
A: There are three kinds of losses: hydraulic loss, volume loss, and mechanical loss.
1) Hydraulic loss: When the fluid flows in the pump body, if the flow channel is smooth, the resistance will be smaller, and if the flow channel is rough, the resistance will be greater, and the water flow will enter the rotating impeller or the water flow will come out of the impeller and cause collision and vortex loss. The above two types of losses are called hydraulic losses.
2) Volume loss: the impeller is rotating, and the pump body is stationary, and a small part of the fluid flows back to the inlet of the impeller in the gap between the impeller and the pump body; In the case of a multistage pump, a portion of the balance disc will also be missing. These losses are called volume losses;
3) Mechanical loss: the shaft should be rubbed with the bearing, packing, etc. when rotating, the impeller rotates in the pump body, and the front and rear covers of the impeller should rub against the fluid, all of which consume a part of the power, and these losses caused by mechanical friction are always mechanical losses.
15. In production practice, what is the basis for the rotor to find balance?
Answer: According to different revolutions and structures, static balance method or dynamic balance method can be used. The static equilibrium of a rotating body can be solved by the static equilibrium method. Static equilibrium can only balance the imbalance of the rotating center of gravity (i.e., eliminate the moment), but not the unbalanced couple. Therefore, static equilibrium is generally only suitable for disc-shaped rotating bodies with relatively small diameters. For rotating bodies with relatively large diameters, the problem of dynamic balancing is often more common and prominent, so it is necessary to carry out dynamic balancing treatment.
16. What is equilibrium and what are the types of equilibrium?
Answer: 1) The work of eliminating the imbalance of rotating parts or parts is called balance, and 2) Balance can be divided into two types: static balance and dynamic balance.
17. What is static equilibrium?
Answer: Where in some special tooling, do not need to rotate the state to determine the front position of the unbalanced rotating parts, and at the same time can determine the position and size of the balance force, this method of finding balance is called static balance.
18. What is dynamic balancing?
Answer: When the part rotates over the part, it is necessary to balance not only the centrifugal force generated by the weight, but also the balance of the moment composed of centrifugal force is called dynamic balance. Dynamic balancing is generally used for parts with high speed, large diameter and particularly strict working accuracy requirements, and accurate dynamic balancing must be done.
19. When doing the static balance of rotating parts, how to determine the bias orientation of the balanced parts?
Answer: first let the balanced part roll freely on the balance tooling several times, if the last time is clockwise rotation, the center of gravity of the part must be located on the right side of the vertical center line (due to friction resistance), at this time at the lowest point of the part with white chalk to make a mark, and then let the part roll freely, the last roll is completed in the counterclockwise direction, then the center of gravity of the balanced part must be located on the left side of the vertical center line, and then use white chalk to make a mark, then the center of gravity of the two records is the bias direction.
20. How to determine the size of the counterweight when doing the static balance of rotating parts?
Answer: First of all, turn the partial weight orientation of the part to the horizontal position, and add the appropriate weight to the maximum circle of the opposite symmetrical position. When choosing the right weight, you should take this into account the part, whether you can carry out counterweight and weight reduction in the future, and after the weight is added, still maintain a horizontal position or a slight swing, and then reverse the part 180 degrees to keep it in a horizontal position, repeat it several times, after the weight is determined to remain unchanged, the weight will be taken off and weighed, which determines the gravity of the balance weight.
21. What are the types of mechanical rotor imbalance?
Answer: Static unbalanced, dynamic unbalanced, and mixed unbalanced.
22. How to make the pump shaft bent to measure?
Answer: after the shaft is bent, it will cause the imbalance of the rotor and the wear of the dynamic and static parts, put the small bearing on the V-shaped iron, the large bearing on the roller support, the V-shaped iron or the bracket should be placed firmly, and then the dial gauge is supported, the gauge is pointed to the shaft, and then slowly disc the pump shaft, if there is a bending, each revolution of the micrometer has a maximum and minimum reading, the difference between the two readings indicates the maximum radial runout of the shaft bending, also known as shaking. The bending degree of the shaft is one-half of the shaking, and the radial runout of the general shaft is not more than 0.05mm in the middle and 0.02mm at both ends.
23. What are the three types of causes of mechanical vibration?
Answer: 1) Structure: caused by manufacturing design defects;
2) Installation: mainly caused by improper assembly and maintenance;
3) Operation: due to improper operation, mechanical damage or excessive wear.
24. Why is rotor misalignment an important reason for abnormal rotor vibration and early bearing damage?
Answer: due to the influence of factors such as installation error and rotor manufacturing, deformation after bearing, environmental temperature change, etc., may cause poor alignment, poor rotor alignment, due to the force change of the coupling, the actual working position of the rotor journal and the bearing is changed, which not only changes the working state of the bearing, but also reduces the natural frequency of the rotor shafting, so the rotor misalignment is an important reason for the abnormal vibration of the rotor and the early damage of the bearing.
25. What is the standard for measuring and reviewing the ellipse and taper of the journal?
Answer: The ovality and taper of the shaft diameter of the sliding bearing should meet the technical requirements, and generally shall not be greater than one thousandth of the diameter. The ovality and taper of the shaft diameter of the rolling bearing are not more than 0.05mm.
26. What should be paid attention to when assembling chemical pumps?
Answer: 1) Whether the pump shaft is bent or deformed;
2) Whether the rotor balance is in line with the standard;
3) the gap between the impeller and the pump casing;
4) Whether the compression amount of the buffer compensation mechanism of the mechanical seal meets the requirements;
5) Concentricity of pump rotor and volute;
6) Whether the centerline of the pump impeller runner and the centerline of the volute runner are aligned;
7) Gap adjustment between bearing and end cover;
8) Gap adjustment of the sealing part;
9) Whether the assembly of the transmission system motor and the variable (increase and reducer) speed changer meets the standard;
10) The coaxiality of the coupling is aligned;
11) Whether the mouth ring clearance meets the standard;
12) Whether the tightness of the connecting bolts of each part is appropriate.
27. What is the purpose of pump overhaul and what are the requirements?
Answer: Purpose: Through the maintenance of the pump, the problems existing after long-term operation are eliminated. The requirements are as follows:
1) Eliminate and adjust the large gap caused by wear and corrosion in the pump;
2) Eliminate dirt, dirt and rust in the pump;
3) repair or replacement of non-conforming or defective parts;
4) Qualified rotor balance test;
5) Check the coaxiality of the pump and the drive machine and meet the standard;
6) The test run is qualified, the information is complete, and the process production needs are met.
28. What is the reason for the excessive power consumption of the pump?
Answer: 1) The total head and the head of the pump do not match;
2) The density and viscosity of the medium are inconsistent with the original design;
3) The pump shaft is inconsistent or bent with the axis of the prime mover;
4) There is friction between the rotating part and the fixed part;
5) Impeller mouth ring wearing;
6) Improper installation of seals or mechanical seals.
29. What are the causes of rotor imbalance?
Answer: 1) Errors in manufacturing: uneven material density, different axiality, non-roundness, uneven heat treatment;
2) Incorrect assembly: the center line of the assembled part is different from the axis;
3) Deformation of the rotor: uneven wear, deformation of the shaft under operation and temperature.
30. What is a dynamic unbalanced rotor?
Answer: There are rotors of equal magnitude and opposite directions, where the unbalanced particles are combined into two couples that are not in a straight line on a day.
31. How to prevent evacuation and cavitation during operation?
Answer: Evacuation: There are gases and liquids in the pump, the pump cannot work, and the flow and pressure tend to zero. Cavitation: It occurs in the pump during operation, and the flow rate and pressure from the pump change and fall, resulting in hydraulic shock. Usually the pumping of the pump refers to a cavitation phenomenon that occurs in the pump, and the evacuation caused by the leakage of the installation technical pipeline and the inhalation of gas is rare, and most of them are caused by changes in operation and process. In the process of operation, the operating conditions should be stabilized, the operating temperature should be taken the lower limit, the pressure should be taken the lower limit, in order to avoid or control the occurrence of cavitation, the flow rate of the pump should be moderate in operation, and the pressure and temperature should be minimized to minimize large changes. The suction line of the pump should prevent the retention of gas, and the inlet of the backup pump should be closed if the inlet pressure is negative.
32. What is a dynamic fit and a static fit, and what is the obvious difference between them?
Answer: 1) dynamic fit: the actual size of the hole is greater than the actual size of the pump; 2) static fit: the actual size of the shaft is greater than the actual size of the hole; 3) obvious difference: dynamic fit, the shaft can do relative motion to the hole; static fit: the shaft and the hole do not have relative motion.
33. What are the four basic requirements for equipment maintenance?
A: Neat, clean, lubricated and safe
34. How does a labyrinth seal work?
Answer: Labyrinth sealing: there are a number of sequentially arranged annular sealing teeth, between the teeth and the rotor to form a series of throttling gaps and expansion space, the fluid through many tortuous channels, through many throttling and produce great resistance, so that the fluid is difficult to leak, to achieve the purpose of sealing.
35. What is the interchangeability of parts?
Answer: 1) The parts can be used interchangeably with each other, and can meet the requirements of the original parts, which is called the interchangeability of parts. 2) It mainly plays a role in facilitating maintenance, reducing maintenance time, improving equipment utilization rate and work efficiency.
36. What is a power pump?
Answer: The power pump continuously transmits energy to the liquid to be conveyed, so that its velocity kinetic energy and pressure energy potential energy are increased, mainly the speed increases, and then its speed is reduced, so that most of the kinetic energy is converted into pressure energy, and the pressure of the conveyed liquid has been raised to transport, such as: 1) vane pump, which includes centrifugal pump, mixed-flow pump, axial flow pump, vortex pump, etc.; 2) jet pump, including gas jet pump, liquid jet pump, etc.
37. What is a positive displacement pump?
Answer: In the process of periodically changing the volume of the pump chamber, the positive displacement pump transmits the capacity to the conveyed liquid with the periodic change of action and displacement, so that the pressure is directly raised to the required pressure value and then conveyed, such as: 1) reciprocating pumps, including piston pumps, piston pumps, diaphragm pumps, extrusion pumps, etc.; 2) rotary lobe pumps, including gear pumps, screw pumps, roots pumps, rotary piston pumps, sliding vane pumps, crankshaft pumps, flexible rotor pumps, peristaltic pumps, etc.
38. What are the main performance parameters of the pump?
Answer: It mainly includes: flow, head, NPSH, speed, power and efficiency.
39. Why should the spare equipment be rolled regularly, and what should be paid attention to when winding?
Answer: 1) For the standby equipment to roll the car regularly, one is to check whether the equipment is flexible and whether there is any jamming, and the other is to prevent the bearing from bending and deforming, so as to really play a standby role.
2) Attention should be paid to the following: first, the stop position of the rotor after the cranking is at an angle of 180 degrees to the original position;
40. What is the harm of exceeding the rated current to the pump?
Answer: the rated current is the current of the motor to do normal work under the condition of rated voltage and rated power, if the rated current is exceeded, the motor is easy to overheat, and the relay protection device acts, so that the pump stops, if the relay protection device does not act or the action is not good, it is easy to burn the motor and damage the pump.
41. What are the main contents of pump inspection?
Answer: 1) Check whether the indicated value of the pressure gauge and ammeter is in the specified area and remains stable;
2) Check whether the operating sound is normal and whether there is any noise;
3) Whether the temperature of the bearing and motor is normal (no more than 60 degrees);
4) Check whether the cooling water is unblocked, whether the packing pump and mechanical seal are leaking, such as whether the leakage is within the allowable range;
5) Check whether the connection parts are tight and whether the anchor bolts are loose;
6) Check whether the lubrication is good and whether the oil level is normal;
42. What work should the device operator do when the maintenance personnel arrive at the post for maintenance?
Answer: 1) Check whether the maintenance work ticket is consistent with the actual equipment number to be repaired;
2) Contact the shift leader and find an electrician in the special area to cut off the power;
3) Provide the maintenance personnel with the damage to the equipment and the specific parts of the maintenance;
4) Cooperate with the maintenance and supervise the quality of the maintenance on site;
5) After the overhaul is completed, contact the power transmission and test run;
6) After the operation is normal, report to the shift leader and make a record at the same time.
43. What is the function of the pump in and outlet valves?
Answer: 1) The pump inlet valve is a part that isolates or cuts off the slurry pump from the system during maintenance, and cannot be used to adjust the flow rate, so it should be fully opened;
2) The outlet valve is a component that regulates the flow rate and isolates the pump from the system and cuts off when it is turned on and off for maintenance.
44. What is the basis for the selection of seals for pumps in chemical production?
Answer: It is selected according to the process conditions, working pressure, and the rotation speed of the medium.
45. What are the types of flat gasket seals?
Answer: 1) Non-metallic gasket sealing;
2) Non-metallic and metal composite gasket sealing;3) Metallic gasket sealing.
46. What are the main causes of gasket leakage?
Answer: 1) Leakage caused by design, improper selection of flange and flange sealing surface form, improper selection of gasket B, improper selection of flange and bolt materials;
2) Leakage caused by manufacturing, installation and operation; a. The machining accuracy of the flange and gasket does not meet the technical requirements; b. When tightening the bolt, the improper operation causes the gasket to deviate; c. The flange seal face is clean and there are impurities.
47. What is a mechanical seal?
Answer: Mechanical seal, also known as face seal, is composed of at least one pair of end faces of vertical rotation axis, under the action of fluid pressure and compensation mechanism, so that the two end faces are tightly fitted and slide relative to each other to form a device to prevent fluid leakage.
48. How many sealing forms are commonly used in pumps?
A: There are two kinds, dynamic seal and static seal.
49. What are the main causes of leakage of mechanical seals?
Answer: 1) There is excessive wear on the sealing end face between the moving ring and the static ring, and the load factor is unreasonable during the design, which causes cracks, deformation, and damage to the sealing end face.
2) Several auxiliary seals are defective or due to improper assembly, and the selection of auxiliary seals is not suitable for working conditions.
3) The spring preload is not enough or after a long period of operation, fracture, corrosion, relaxation, coking, and the suspended particles or crystals of the working medium accumulate for a long time and are blocked in the spring gap, resulting in spring failure, compensation sealing ring can not float, and leakage;
4) Due to the excessive perpendicularity deviation between the sealing end face of the dynamic and static ring and the center line of the shaft, the sealing end face is not tightly bonded and causes leakage;
5) Due to the large axial channeling momentum of the shaft, the fittings related to the seal are not well matched or of good quality, and it is easy to leak.
50. What is the material of the friction pair of the mechanical seal?
Answer: It should be selected according to the nature of the medium, working pressure, temperature, sliding speed and other factors, and sometimes the ability to withstand short-term dry friction when starting or liquid film breaking.
51. What are the effective ways for labyrinth sealing to increase the resistance of the medium?
Answer: 1) reduce the gap, 2) strengthen the vortex, 3) increase the number of sealing teeth, 4) try to convert the kinetic energy of the air flow into heat energy
52. How does a floating ring seal work?
Answer: The floating ring sealing is based on the throttling effect generated in the narrow gap between the shaft and the floating ring, and the sealing oil higher than the gas pressure is injected into the gap to achieve the purpose of sealing the gas.
53. What is the reason for the increase in the leakage of the floating ring seal?
Answer: 1) The floating ring is used for a long time, and the normal wear and tear increases the gap;
2) The surface of the lining of the floating ring hole is rough, the precision is low, and the gap increases due to short-term wear;
3) Deflection caused by improper assembly, the centering accessories fall off, so that the oil flows out from other gaps, and the leakage increases;
54. What is the function of the oil stop, and how to measure and adjust the oil block clearance?
Answer: 1) The function of the oil stop is to prevent the bearing lubricating oil from flowing along the journal to the outside of the bearing, and there are two installation positions of the oil baffle: one is on the bearing seat, and the other is on the bearing;
2) The oil block clearance can be measured with a measuring tape when the oil block is disassembled or assembled. For the bearing pad in the oil gear clearance can be appropriately relaxed, the face of the bearing seat on the oil gear clearance requirements are more stringent, generally the lower part is 0.05-0.10mm, the two sides are 0.10-0.20mm, and the upper part is 0.20-0.25mm.
55. What are the factors that affect the sealing of the labyrinth?
Answer: 1) The radial clearance is too large, or the clearance of the newly replaced air sealing ring is too small;
2) The sealing sheet or air seal ring and between the teeth become dull due to wear, or deformed after long-term wear and heat, resulting in damage and cannot be used;
3) After long-term use, the spring becomes relaxed and deformed, so that the air sealing ring can not be in place, after operation, the precipitation and accumulation of dust and dirt are the pressure of the sealed medium is lower than the pressure of the working medium or the pressure is unstable.
56. What are the common types of dynamic seals?
Answer: Leather bowl seal, expansion ring seal, spiral seal, pneumatic seal, hydraulic seal, centrifugal seal, packing seal, labyrinth seal, mechanical seal, etc.
57. What are the main factors that affect sealing?
Answer: 1) the quality of the seal itself, 2) the process operation conditions, 3) the assembly and installation accuracy, 4) the accuracy of the host itself, 5) the sealing auxiliary system
58. What are the components of mechanical seals?
Answer: The mechanical seal is composed of a static ring, a moving ring, a compensation buffer mechanism, an auxiliary sealing ring and a transmission mechanism. The end faces of the static ring and the moving ring are perpendicular to the axis of the pump and fit each other to form a rotating sealing surface. The static ring and the gland, the moving ring and the shaft are all sealed with auxiliary sealing rings, so as to compensate for the action of the buffer mechanism to promote the sealing ring to move along the axial direction, keep the end face of the moving ring and the static ring close to each other, and compensate for the wear of the end face of the sealing ring.
59. What are the characteristics of mechanical seals?
Answer: 1) The sealing performance is good, the leakage of the mechanical seal is generally 0.01-5ml/h, according to the special requirements, after special design, the leakage of the mechanical seal manufactured is only 0.01ml/h, or even smaller, and the leakage of the packing seal is 3-80ml/h (according to the relevant regulations of the mainland, when the shaft diameter is not greater than Φ50mm, it is less than or equal to 3ml/h, and when the shaft diameter is equal to Φ50mm, it is less than or equal to 5ml/h);
2) Long service life, generally more than 8000h;
3) The friction power is small, only 20%-30% of the packing seal;
4) There is no relative movement between the shaft and the bushing and the seal, no friction will be generated, and the service life of the shaft and the sleeve is long;
5) The sealing surface of the mechanical seal is perpendicular to the pump axis, and the seal displaces at any time when the pump shaft vibrates, so the vibration can still maintain good sealing performance when the vibration is in a certain range; 6) The mechanical seal relies on the pressure of the sealing fluid and the spring force to keep the static and dynamic ring sealing surfaces fit, and relies on the spring force to compensate for the amount of wear, so once the deployment is appropriate, the pump generally does not need to be adjusted frequently in operation, which is easy to use and has a small maintenance workload;
7) It can be used in a wide range of working conditions, which can be used under high temperature, low temperature, high pressure, high speed and strong corrosion conditions;
8) Troubleshooting and parts replacement are inconvenient, and maintenance can only be carried out after stopping;
9) The structure is complex, the assembly accuracy is high, and the assembly and installation have certain technical requirements;
10) High manufacturing price
60. What are the main characteristic parameters of mechanical seals?
Answer: 1) Shaft diameter: The shaft diameter range of the pump mechanical seal is generally 6-200mm, and the special shaft diameter can reach 400mm, and the shaft diameter of the pump is usually determined by the strength requirements and rounded or modulated with a shaft sleeve to meet the standard shaft diameter of the mechanical seal;
2) Speed: generally the same as the speed of the pump, the speed of the general centrifugal pump is less than or equal to 3000r/min, the high-speed centrifugal pump is less than or equal to 8000r/min, and the special pump is less than or equal to 4000r/min;
3) Average circumferential linear velocity of sealing surface: refers to the circumferential linear velocity of the average diameter of the sealing end face. The average linear velocity of the sealing surface is greater, and the heating and wear of the sealing surface (i.e., the friction pair) are larger. Generally, the circumferential linear velocity of the receiving and unloading seal is less than or equal to 30m/s, the circumferential linear velocity of the spring-static mechanical seal is less than or equal to 100m/s, and the special can be less than or equal to 150m/s.
4) Specific pressure of the end face: The specific pressure of the end face Pc is the contact pressure (MPa) on the sealing surface. The specific pressure of the end face seal should be controlled within a reasonable range, too small will reduce the sealing performance, too much will aggravate the heating and wear of the sealing cover. Reasonable specific pressure value of the end face of the mechanical seal for pump: built-in mechanical seal, generally take Pc=0.3-0.6MPa; Externally mounted, take Pc=0.15-0.4MPa. When the lubricity is good, the specific pressure of the end face can be increased appropriately, and the specific pressure of the end face can be increased for the liquid with large viscosity, which can be taken Pc=0.5-0.7MPa, and the liquid with volatile and poor lubrication should take a smaller specific pressure of the end face, which can be taken Pc=0.3-0.45MPa.
61. What are the contents of the inspection before the assembly of the mechanical seal?
Answer: 1) General inspection: mainly check the model, specification, performance, fit size of each part and whether there are gaps, pits, deformation and cracks and other damages.
2) Inspection of dynamic and static rings: the sealing end face should be smooth and bright, and defects such as material collapse, pits, grooves, and scratches should be present. For graphite rings, it is also necessary to dip and not check for cracks.
62. How to check the parallelism, perpendicularity and surface roughness of the end face?
Answer: 1) The flatness of the end face is 0.0006-0.0009mm for liquid medium and 0.0001-0.0004mm for gas medium;
2) Tolerance of balance: the parallelism deviation of the sealing end face to the contact surface of the sealing ring, generally the sealing ring is less than or equal to 0.04mm. The parallelism deviation of the two end faces of the inlay ring (ceramic ring and cemented carbide ring) should be less than or equal to 0.03mm;
3) Perpendicularity tolerance: for the perpendicularity deviation of the center line of the outer diameter at the installation sealing ring, the full diameter should be less than or equal to 0.03mm;
4) Surface roughness: the hard material of the sealing surface (obtained by the method of removing the material) the dark glossy surface (obtained by grinding), the soft material (obtained by the method of removing the material) can not see the processing traces, the processing direction is slightly distinguished (grinding, fine turning is obtained), the contact with the auxiliary sealing ring is (obtained by the method of removing the material) the processing traces are invisible, the processing direction is micro-identified (grinding, fine turning is obtained), and the rest is (obtained by the method of removing the material) micro knife marks (knife twisting, fine turning is obtained).
63. What are the requirements for the inspection of mechanical seals and auxiliary seals?
Answer: 1) The surface of the auxiliary sealing ring is smooth and flat, and there shall be no bubbles, cracks, notches and other defects; the size of the end face should be uniform; the burr of the "O" seal ring should be at an angle of 45 degrees with the working surface;
2) The hardness of the auxiliary sealing ring should be selected according to the pressure, the higher the sealing pressure, the higher the hardness, the lower the hardness. Synthetic rubber is commonly used in auxiliary sealing rings;
3) The inner diameter of the "O" shaped sealing ring on the cylindrical surface should be 0.5-1mm smaller than the outer diameter of the sealing point. The inner diameter of the "O" ring of the moving ring is relatively small, and the inner diameter of the "O" ring of the static ring is smaller than that of the static ring;
4) The compression amount of the auxiliary seal should be appropriate, the compression amount is too large, the sealing effect is good, but the friction resistance is large, the assembly is difficult, and the swimming compensation ability is poor in work. The compression amount is too small, the frictional resistance is small, the assembly is easy but the sealing effect is poor. The "O" ring of the dynamic and static ring of the mechanical seal is a cylindrical seal, and its compression is about 8%-23% of the diameter of the cross-sectional smooth surface. If the diameter is small, take a percentage, and if the diameter is large, take a smaller percentage.
5) The compression of the "O" ring should consider its other functions, such as the static ring without anti-repinning, the static ring "O" ring plays the dual role of sealing and anti-rotation, and the compression amount of the "O" ring should be larger, so as to avoid the rotation of the static ring and the failure of the seal. The "O" shaped sealing ring of the moving ring, under the premise of ensuring the sealing effect, the compression amount should be smaller, so as to avoid excessive compression and excessive resistance, and cannot be floated to compensate.
64. What are the contents of the inspection of mechanical seal springs?
Answer: The inspection of the spring includes: the total number of turns, the number of effective turns, the free height, whether the axial end face is perpendicular, and the direction of spring rotation. But springs must check the direction of rotation, and multi-springs do not need to check the direction of rotation. The original free height of the new spring should be checked, the free height should be measured and compared with the original record, and the residual deformation should be replaced if it is too large. After the old spring is cleaned, its elasticity should be measured, and the elastic force should be replaced if the elasticity is reduced by 20%. For multi-spring mechanical seals, the free height difference of each spring shall not be less than 0.5mm.
65. What are the requirements for the inspection of the shaft and bushing before the installation of the mechanical seal?
Answer: 1) Check the matching size, surface roughness, chamfering, axial momentum and radial runout of the shaft (or bushing), etc., and check the mating clearance between the shaft and the bushing. The surface roughness of the shaft diameter (or bushing) of the installed mechanical seal should be less than 1.6, and the axial channeling of the shaft should not be greater than 0.25mm. The shaft sleeve shall not be axial axial channeling, and the radial circular runout of the shaft or shaft sleeve shall be allowed.
2) Check the wear of the shaft and bushing. Because of the mechanical vibration and the floating of the compensation of the moving ring, the shaft and shaft sleeve may also be worn by the "O" ring, if it is worn, it should be repaired or replaced;
3) The shaft sleeve seat and shaft sleeve should be in good condition
66. What are the inspection contents of the sealed end face or sealed box?
Answer: The roughness of the surface in contact with the static ring sealing ring is 1.6, and the round runout of the end face shall not be greater than 0.06mm after assembling the static ring. The sealing end face or sealing cavity should be free of burrs, and the chamfer radius should be too sufficient, and it should be smooth. The size of the sealing end face or the inner diameter of the sealing cavity shall meet the requirements.
67. What is the "six determinations" of pump patrol inspection?
Answer: Set the route, set the person, time, set the point, set the responsibility, and set the requirements for inspection.
68. How many types of maintenance are there for chemical machine pump maintenance?
A: There are three main forms: 1) maintenance and overhaul, 2) unplanned overhaul, and 3) planned overhaul.
69.What are the precautions for assembling the auxiliary seal?
Answer: 1) The rubber auxiliary sealing ring cannot be soaked and washed with gasoline and kerosene, so as to avoid expansion and deformation and premature aging;
2) The "O" shaped sealing ring is installed on the static ring assembly, which should be logical and not distorted, and is the cross-section when the burr is in a free state;
3) When advancing the assembly, it is necessary to prevent damage to the "O" seal. The main forms of damage are: lumps, tears, bruises, crimping, and twisting.
70. What are the causes of the tear of the "O" ring of the mechanical seal?
Answer: The surface of the shaft is rough or burr, the old shaft or bushing is injured by the fastening screw, and it is not polished and smooth before assembly, and the edges of the keyway and anti-reeling groove are not properly trimmed.
71. What are the requirements for the debugging of the compression amount of mechanical seal springs?
Answer: The mechanical seal spring transmission screw compresses an amount, which is called the compression amount of the spring. After all the mechanical seals are installed, there is another amount of compression relative to the spring, which is called the compression of the mechanical seal. The total compression of the mechanical seal spring is the sum of the compression of the transmission screw and the spring's own elastic force. During assembly, the greater the compression of the mechanical seal, the less force the spring exerts on the moving ring. Therefore, the working principle of the mechanical seal, the size of the spring has a great impact on the performance and life of the mechanical seal, so the assembly must adjust the compression amount according to the technical requirements.
72. What are the precautions for the installation of static ring components?
Answer: 1) Put the inspected static ring sealing ring from the tail of the static ring, and load the static ring assembly into the gland or sealing cavity. Under no circumstances should impact force be applied to mechanical seal parts or components. The pressed surface should be padded with clean cardboard or cloth to avoid damaging the sealing end face.
2) After assembling into a rotating dynamic ring assembly or a static static ring assembly, press the compensation ring by hand to check whether it is installed in place and whether it is flexible, and whether the elastic opening is positioned reliably.
3) Whether the perpendicularity between the sealing end face and the center line of the shaft or shaft sleeve meets the requirements.
4) For static mechanical seals, the anti-transfer pin lead of the static ring assembly should be accurate, and when the static ring group is promoted, the pin groove of the component should be aligned with the pin, and after advancing in place, the distance from the end face of the component to a certain end face of the sealing cavity should be measured to judge whether it is installed in place;
5) When tightening the bolt to press the end cover, the force should be uniform and symmetrical, and it should be screwed several times, and it should not be tightened at one time, so as not to deflect or even crush the graphite ring.
73. What are the requirements for the inspection of mechanical seals after assembly?
A: After the mechanical seal is assembled, two inspections should be done.
1) Turning inspection. Because it has not been filled with liquid, there is only a small amount of lubricating oil on the end face of the dynamic and static ring seal, so it is not advisable to turn more than one car, so as not to damage the seal end face.
2) Filling test. Check whether there is leakage, if there is no leakage, you can do a test test.
74. What is the inspection standard for the leakage point of the dynamic seal?
Answer: 1) The sealing point of the packing is not more than 15 drops per minute;
2) The mechanical seal point is not allowed to leak at the beginning, and no more than 15 drops per minute at the end of the period;
3) The gear oil pump allows micro-leakage, no more than 1 drop per minute;
4) Micro leakage is allowed in all kinds of oil injectors, and it should not exceed 1 drop per minute.
75. What are the requirements for the filling of the pressure flange filler?
Answer: 1) The packing should be cut into a 45-degree angle, the incision should be pressed into the upper and lower towers, and the fractures of the adjacent two circles should be staggered at an angle of about 90 degrees;
2) The packing should not be pressed too tightly, the gland bolt should be symmetrically closed, evenly pressed, and the depth of the gland pressed into is generally the height of a circle of packing, but not less than 5mm.
76. What preparations should be made before mechanical installation of packing?
Answer: 1) Selection of filler: according to the form of filler and the pressure, temperature and corrosion performance of the medium, the medium, form, size and performance of the filler should meet the requirements and standards of the equipment;
2) Before the packing is installed, the packing box should be cleaned, inspected and trimmed, and the damaged parts should be replaced;
3) Check the fitting gap between the shaft, gland and packing.
77. What are the types of lubrication forms?
Answer: 1) drip oil lubrication, 2) oil mist lubrication, 3) splash lubrication, 4) pressure lubrication, 5) dry oil cup lubrication;
78. What factors should be considered in the selection of lubricating oil?
Answer: 1) Motion speed, 2) Motion properties, 3) Operating temperature, 4) Pressure relationship, 5) Mating properties of friction surfaces, 6) Surface roughness
79. What are the functions of lubricants?
Answer: 1) Cooling effect, 2) Anti-rust effect, 3) Cooling effect, 4) Flushing effect, 5) Friction control effect, 6) Wear reduction effect, 7) Vibration damping effect, 8) Sealing effect;
80. What are the applications of calcium-based grease, sodium-based grease and lithium-based grease?
Answer: 1) Calcium-based grease: water-resistant, can be used in humid working places, but not high-temperature resistance, the temperature range of use is -10-60 degrees;2) Sodium-based grease: high temperature resistance, but not water resistance, the temperature range of use is -10-110 degrees;3) Lithium-based grease: with heat resistance, water resistance, the temperature range of use is -20-1200 degrees;
81. What are the "five determinations" of pump lubricating oil management?
Answer: The pump should be fixed, timed, qualitative, quantitative, fixed, and checked to ensure the normal operation of the pump;
82. What is the basic principle of the importance of lubrication to pumps?
Answer: The lubricant can be firmly attached to the friction surface of the parts to form an oil film, which is strongly combined with the friction surface of the parts, and the two lubricating surfaces are separated by lubricants, so that the friction of the parts becomes the friction of the lubricant molecules, so as to reduce friction and wear and extend the service life of the parts.
83. What are the causes of oil leakage from oil-lubricated pumps?
Answer: 1) The oil level is too high, and the inner holes of the bearing cover at both ends of the bearing box leak oil; 2) The static sealing point leaks, such as the oil drain wire plugs the oil leakage; 3) The bearing gland and the bearing joint surface leak oil;
84. What role does the lubricant play during the rotation of the bearing?
Answer: 1) lubrication, 2) cooling, 3) washing, 4) rust prevention, 5) sealing, 6) buffering and vibration damping, 7) anti-friction and wear;
85. What are the main properties of lubricating oil?
Answer: Acid number, viscosity, viscosity index, flash point, mechanical impurities, freezing point, carbon residue, ash.
86. How many ways are there to measure the clearance of radial plain bearings?
Answer: There are three commonly used methods: lead pressing method, shaft lifting method, and false shaft method. Shaft lifting method: install a dial gauge at the shaft diameter close to the bearing pad, install a dial gauge at the top of the bearing shell when used, gently lift the shaft diameter until it touches the upper pad, but can not make the movement of the upper tile shell too large, at this time the dial gauge reading on the shaft diameter minus the movement of the upper tile shell is the bearing clearance.
87. What are the faults of sliding bearings and how to deal with them?
Answer: Fault: gluing.
Treatment measures: 1) Ensure the correct installation position and clearance requirements, 2) Ensure good lubrication of the rotor. Fault: Fatigue rupture. Treatment measures: 1) the bearing surface should be kept smooth, 2) to ensure a good balance of the rotor.
Faults: Wear and tear.
Treatment measures: 1) avoid insufficient lubrication, 2) clean the lubrication system in time.
Fault: Abrasion.
Treatment measures: 1) Prevent instantaneous oil cut-off, 2) Avoid bumps during installation or disassembly.
Fault: Brushing. Treatment measures: pay attention to the cleanliness of the oil circuit to prevent dirt from entering. Fault: Cavitation.
Treatment measures: 1) increase the oil supply pressure, 2) modify the shape of the bearing oil groove and oil groove, 3) reduce the bearing clearance.
Fault: Electrical erosion.
Treatment measures: 1) ensure that the insulation condition and protection device of the machine are good, 2) ensure that the grounding of the machine is intact, 3) check the shaft diameter, if there are electric erosion pits on the shaft diameter, the shaft diameter should be polished to remove the pits.
88. What are the reasons for the gluing phenomenon of sliding bearings in use?
Answer: 1) The bearing is overheated, 2) The load is too large, the oil quantity is insufficient, 4) The operation is improper or the temperature control is out of order.
89. What are the causes of abnormal noise when rolling bearings are running?
Answer: 1) The rolling element or raceway is seriously peeled off and the surface is uneven. 2) The bearing accessories are not properly installed, loose or friction. 3) There are iron filings or dirt in the bearing. 4) Lack of lubricant.
90. What are the types of radial clearance of rolling bearings?
Answer: 1) Original clearance: the clearance in the free state before the bearing is installed. 2) Fitting clearance: the clearance after the bearing is installed on the shaft or in the hole, its size is determined by the interference, and the fitting clearance is less than the original clearance. 3) Working clearance: Some bearings, due to the characteristics of the structure, the clearance can be determined by adjusting the mutual position of the bearing rings in the process of assembly or use, such as radial thrust ball bearings.
91. What problems should be paid attention to when selecting rolling bearings?
A: 1) The direction and nature of the load. 2) Requirements for self-alignment performance. 3) Bearing speed. 4) Economy. 5) High or low accuracy.
92. How to choose the lubrication method of rolling bearings?
Answer: The normal operation of the bearing is related to lubrication, the temperature of the conveyed medium is 80 degrees, and the speed is below 2950r/min, dry oil lubrication is used, and when the temperature of the conveying medium exceeds 80 degrees and the power is large, thin oil lubrication is used.
93. How to check the quality of rolling bearings?
Answer: There should be no holes, dents, peeling and peeling on the surface of the rolling element and raceway. The rotation is flexible, and after turning by hand, it should be decelerated and stopped smoothly and gradually, and it cannot be stopped suddenly or vibrate. There should be a certain gap between the cage and the inner and outer rings, and the isolation rack can be pushed radially by hand for experiments. The clearance is suitable within the standard range and is measured by the lead pressing method.
94. What should be paid attention to when disassembling and assembling rolling bearings?
Answer: 1) The force application part should be correct, the principle is that the shaft should match the inner ring and the outer ring with the shell to avoid deformation or bump of the rolling element and the raceway. 2) To apply force symmetrically, not only one side, causing the bearing to deviate and gnaw the journal. 3) Before disassembly, the shaft and bearing should be cleaned, and there should be no rust and burrs.
95. What happens if there is too much oil in the bearing box?
Answer: The bearing box is filled with too much oil, and the bearing has no space for heat dissipation, which will cause the bearing to heat up.
96.How do I check the radial clearance of a rolling bearing?
Answer: with the lead pressure method and feeler gauge method for measurement, the radial clearance translation is not marked in the bearing code, the clearance of the bearing is different according to the size of its inner diameter, check the table to determine, under normal circumstances, the radial clearance of the rolling bearing can not be greater than three thousandths of the inner diameter of the bearing, and the radial clearance of the centripetal short cylindrical bearing can not be greater than two thousandths of the inner diameter of the bearing.
97. Why should rolling bearings be preloaded?
Answer: When assembling a radial thrust ball bearing or a radial ball bearing, if a certain axial load is applied to the inner and outer rings of the bearing, the relative displacement of the inner and outer rings will occur, which eliminates the gap between the inner and outer rings and the rolling elements, and produces the initial elastic deformation, and the preloading can improve the rotation accuracy and life of the bearing, and reduce the vibration of the shaft.
98.How to achieve rolling bearing preload?
Answer: 1) Preload with the thickness difference between the inner and outer gasket rings of the bearing. 2) Use a spring to achieve preloading, and rely on the spring acting on the outer ring of the bearing to make the bearing preload. 3) Grinding and narrowing the inner or outer rings used in pairs to achieve preloading. 4) Adjust the axial position of the inner ring of the bearing tapered bore to achieve preload.
99. What is the principle of substitution for rolling bearings?
Answer: 1) The technical parameters such as the working capacity coefficient and allowable static load of the bearing should be equal to or higher than the technical parameters of the original bearing.
2) The allowable limit speed should be equal to or higher than the actual speed of the original bearing.
3) The accuracy grade of the substitute bearing should not be lower than the accuracy grade of the original bearing.
4) The size should be the same, and the size of the machine and the bearing should not be changed arbitrarily because of the replacement of the bearing.
5) For bearings using the nesting method, the concentricity of the inner and outer cylindrical surfaces of the nesting should be ensured, and the tolerances and fits should be correctly selected.
100. What are the fixing methods of rolling bearings?
Answer: 1) Unilateral force bidirectional fixation, 2) Bilateral force single fixation, #) Mixed fixation
101. On what basis is the bearing oil level determined?
Answer: For rolling bearings, the lowest bead centerline of the bearing is the normal oil level, the lower third of the ball is the low oil level, and the two-thirds above the centerline of the ball is the high oil level, and the oil ring is generally 1.5-2 times the diameter of the lubricated spindle than the lubricated spindle. The oil level of the oil chamber should be a certain distance from the spindle oil, which is generally about half of the diameter of the spindle or about 5mm below the high oil level from the bearing.
102. Why is it not good for the bearing oil level to be too high or too low?
Answer: 1) The oil level of the bearing is too low, so that some parts of the bearing cannot be lubricated, so the bearing will produce wear and heat, so that the bearing burns out. 2) The oil level is too high, with the rotation of the spindle, the rolling bearing and the oil ring are easy to leak oil from the shaft seal in the process of oil; the oil level is too high, and the rotation of the oil ring is also hindered, resulting in the bearing heating.
103. What are the requirements for oil filling for bearings lubricated with grease?
Answer: 1) For low speed (speed less than 1500r/min) mechanical filling oil volume is generally not more than two-thirds of the whole bearing chamber; 2) for mechanical filling oil volume above 1500r/min generally should not be more than half of the whole bearing chamber.
104. What are the causes of high bearing temperature?
Answer: 1) The oil level is too low, and the amount of oil entering the bearing is reduced. 2) The oil quality is unqualified, water or impurities enter, and the oil emulsion deteriorates; 3) The oil ring does not rotate, and the oil supply of the bearing is interrupted. 4) Insufficient bearing cooling water, 5) Bearing damage, 6) Bearing gland exerts too much or too little tightening force on the bearing, or crushes the radial clearance, and loses flexibility.
105. What are the requirements for the performance of the plain bearing lining material?
Answer: 1) There should be enough strength and plasticity, and the bearing lining can not only withstand a certain working pressure, but also evenly distribute the pressure between the journals. 2) It has good foaming and abrasion resistance. 3) Good lubrication and heat dissipation performance. 4) It is necessary to have good process performance.
106. What material is used to make the tile shell of the sliding bearing?
A: Cast steel, forged steel, cast iron
107. As a rule of thumb, how much is the radial clearance of the bearing?
Answer: According to the bearing of different structural forms, one thousandth to three thousandths of the shaft diameter can be taken.
108. What is the effect of the clearance size of the plain bearing?
Answer: 1) The gap is small and the precision is high, but too small can not ensure lubrication and cannot form an oil film. 2) The gap is large, the precision is low, it is easy to run out, and the oil film is unstable.
109. What are the items of bearing inspection?
Answer: 1) Whether the position of the journal friction mark on the tungsten gold surface is correct, and the scraping knife flower at the place is polished or rubbed.
2) Whether the tungsten gold surface is scratched, damaged and corroded.
3) Tungsten gold has numerous cracks, local spalling and degeneration (can be tested by wooden stick percussion or oil immersion method).
4) Whether there is wear and corrosion on the bearing force or spherical surface of the horn, whether the horn screws are loose and whether the horn is intact.
110. What are the advantages of tilt pad bearings?
Answer: The advantage of tilting tile is that each tile can swing freely, which can form the best oil film in any situation, and the high-speed rotation stability is good, and the oil film is not easy to oscillate.
111. What kind of bearing position is not qualified bearing?
Answer: 1) Loss of original rotation accuracy, 2) Noise in operation, 3) Large rotation resistance.
112. What are the causes of overheating of the rolling bearings of centrifugal pumps?
Answer: 1) The axial clearance of the rolling bearing is small, 2) The installation direction is incorrect, 3) Dry wear or looseness, 4) The lubricating oil quality is not good, the oil quantity is insufficient or the circulation is not good, 5) The oil slinger ring is deformed and cannot be oiled.
113. What is the scrapping standard for rolling bearings for pumps (radial ball bearings)?
Answer: 1) The inner and outer ring raceways are peeling off, seriously worn or cracked. 2) The rolling element is out of roundness or the surface is peeling off and there are cracks. 3) The cage is seriously worn or deformed, and the rolling elements cannot be fixed. 4) There is noise or vibration when rotating, braking phenomenon and reverse reversal when stopping. 5) The fitting clearance of the bearing exceeds the maximum value of the specified clearance.
114. What is the reason for the phenomenon of fish scale peeling on the track surface of the inner ring and outer ring of the bearing or the rolling surface of the rolling element?
Answer: 1) excessive load, 2) poor installation, 3) foreign matter intrusion, lubricant is not suitable, 4) bearing clearance is not suitable, 5) shaft, bearing box accuracy is not good, bearing box rigidity is uneven, shaft deflection is large, 6) rust, erosion points, abrasions and indentation.
115. What are the properties of bearing alloys?
Answer: 1) low coefficient of friction to reduce the wear of the shaft, 2) high plasticity, so that the shaft and bearing pads are well run-in, 3) good thermal conductivity, 4) sufficient compressive strength and fatigue strength.
116. What are the properties of high-speed rotating plain bearings?
Answer: 1) It should be able to bear radial and axial loads, 2) It also requires a small friction coefficient, 3) It has a long service life and stable and reliable operation under the command.
117. What are the causes of rolling bearing vibration?
Answer: 1) Random vibration transmitted by rolling elements. 2) Random vibration due to improper installation and lubrication. 3) Vibration from the outside of the bearing.
118. What are the assembly requirements for rolling bearings?
Answer: 1) The end face marked with the model number on the bearing should be installed in the visible part for easy replacement.
2) The arc radius at the shoulder of the journal or shell hole should be less than the arc chamfer radius of the bearing end face, so as to ensure that the bearing is close to the shoulder and the shell hole shoulder after assembly.
3) The fixing device of the bearing must be intact and reliable, with a moderate degree of tightness and reliable relaxation.
4) During the assembly process, keep it clean to prevent debris from entering the bearing;
5) After assembly, the bearing rotates flexibly, without noise, and the general temperature rise does not exceed 50 degrees.
119. What are the lining materials of common sliding bearings, and what are the characteristics of each?
Answer: 1) Gray cast iron, which is used in the case of low speed, light load and no impact load, commonly used are HT15-33 and HT20-40.
2) Copper-based bearing alloys. ZQSn10-1 phosphor tin bronze and ZQA19-4 aluminum bronze are commonly used, which are suitable for medium speed, high turbidity and impact load conditions.
3) Oil-impregnated bearings: generally made of bronze, cast iron powder and an appropriate amount of graphite pressed into shape, sintered at high temperature into porous materials. It is often used in low-speed or medium-speed, light-load, and inconvenient lubrication occasions.
4) Nylon. Nylon 6, nylon 66 and nylon 1010 are commonly used, and nylon bearings have the advantages of good running and harmony, the soft surface of debris after wear does not hurt the journal, good corrosion resistance, poor thermal conductivity, and will expand after water absorption.
5) Bearing alloy (babbitt). It is an alloy of tin, lead, copper, antimony, etc., which has good wear resistance, but has low strength and cannot be made into bearings alone, and is usually cast on bronze, cast iron, steel and other bearing substrates.
6) Three-layer load bearing material. There are two commonly used types: polypropylene fluoride steel body composite material and polyoxymethylene steel body composite material.
120. What is the reason for the high temperature rise of rolling bearings?
Answer: 1) During installation and operation, there are impurities or dirt invading.
2) Use inappropriate lubricants or insufficient lubricating oil.
3) Friction occurs between sealing devices, hot rings, bushings, etc., or the fit is loose, causing friction.
4) Incorrect installation, such as the inner and outer rings are deviated, the mounting seat holes are not concentricity, the raceway is deformed and the gap is not adjusted properly.
5) When the wrong type is selected, when the inapplicable bearing is selected, it will heat up due to overload or high speed.
121. How to install a radial ball bearing on the shaft, if the knocking method is adopted?
Answer: Hit the bearing ring symmetrically with a steel sleeve, copper sleeve or copper rod, evenly knock into the specified position, it is forbidden to knock on the outer ring of the bearing, so as not to damage the bearing, after the installation is completed, check that the outer ring of the rotating bearing should be flexible and free, without blockage.
122. What are the common disassembly methods of rolling bearings?
Answer: percussion method, pull out method, push method, hot dismantling method.
123. What should be paid attention to when disassembling a rolling bearing (bearing on the shaft) by percussion method and pull-out method?
Answer: 1) The knocking force should generally act on the inner ring of the bearing, and should not be knocked on the rolling element and cage, and the outer ring of the bearing is not allowed. 2) When using the pull-out method, the inner ring of the bearing should be pulled, and the outer ring of the bearing should not be pulled only to avoid excessive loosening or damage to the bearing.
124. How to set up a dial gauge when the sliding bearing uses the shaft lifting method to measure the clearance?
Answer: install the bearing, do not tighten the bolts, set the dial gauge on the back of the upper tile, set the dial gauge at the shaft diameter, and gently lift the shaft not too high, until the dial gauge pointer on the back of the tile can move.
125. What are the assembly requirements for split radial plain bearings, bearing covers and bearing housings?
Answer: When assembling, the bearing back should be in good contact with the cover and seat hole, and the contact area should not be less than 40%-50% of the entire area, and there should be no gaps in the uniform distribution, otherwise it will need to be repaired. The fixing pins and screws of the fixed sliding bearing should be buried 1-2mm in the bearing body. The gasket should be the same as the shape of the tile mouth, and its width should be less than 1mm on the inside of the bearing. The gasket should be flat and free of edges, and the thickness of the gasket on both sides of the tile mouth should be consistent.
126.How to adjust the clearance of split radial plain bearings?
Answer: 1) Adjust the gasket at the joint surface to make the top clearance and side clearance of the shaft and bearing meet the requirements. In the absence of regulations, one to two thousandths of the journal can be taken as a rule of thumb, and should be selected within this range according to speed, load and lubrication.
2) The side clearance is generally one-half of the top clearance.
3) If the structure does not allow the gasket, it is necessary to adjust the clearance by repairing the tile mouth of the bearing. While repairing and studying the adjustment gap of the tile, it is necessary to ensure that the lower and upper tiles should be tightly fitted, not more than 0.05mm.
127. What are the main forms of rolling bearing damage?
Answer: 1) fatigue pitting, 2) abrasion, 3) burns, 4) electrical erosion, 5) cage damage, 6) inner and outer ring fracture, 7) ball loss of roundness, 8) raceway surface peeling.
128. What are the characteristics of the key connection?
Answer: Relying on the side of the key to transmit torque, the parts on the shaft are only circumferentially fixed, and can not bear the axial force.
129. What are the assembly requirements for loose key connections?
Answer: For ordinary flat keys, semi-circular keys and guide keys, after assembly, it is required that there should be some interference on both sides of the key, the top surface of the key should leave a certain gap, and the bottom surface of the key should be in contact with the bottom surface of the shaft groove. For slide keys, the side keys are in contact with the bottom surface of the wheel groove, while the key has a gap with the bottom surface of the shaft groove.
130. What are the preparation steps for loose key connections?
Answer: 1) Clean the burrs on the keys and keyways.
2) The file is matched with the key length, and there should be a gap of about 0.1mm between the key head and the shaft groove.
3) Use the key head and keyway to match, for the ordinary flat key, flat round key and guide key, the key can only be embedded in the shaft groove, and the slide key should be embedded in the wheel groove.
4) Cooperate with the surface to add oil, and install the key on the shaft with a copper rod or a hammer cushion.
131. Precautions for installation and disassembly of ordinary flat keys and shaft grooves?
Answer: Before installation, check and remove the burr and flash of the keyway, check the straightness of the key, leave a gap of 0.1mm between the key head and the length of the keyway, and add oil on the mating surface to press the key into the keyway. Before disassembly, the key should be gently struck, loosened and used a small flat shovel or screwdriver to pick up the key from the end of the key, and it is strictly forbidden to hit or lift out from the side of the key.
132. What are the requirements for the coordination of the key and the shaft?
Answer: 1) The fit between the key and the keyway should not have problems on both sides, and there should generally be a gap of 0.1-0.4mm at the top. 2) Do not use the method of padding or twisting to increase the tightness of the key.
133. What are the four forms of coupling alignment and analysis deviation?
Answer: Concentric parallel, concentric non-parallel, parallel non-concentric, non-concentric.
134. What is a one-point measurement?
Answer: The method of measuring the axial and radial clearance of a certain position of the coupling at the same point at the same time is called one-point measurement.
135. What is the principle of coupling alignment?
Answer: coupling alignment mainly measures its radial displacement and angular displacement, when the two axes are in different axes, the relative deviation between the outer ring or the end face of the two couplings, according to the measured deviation value can calculate the deviation value of the axial line, in order to obtain the correct measurement results, the two rotors must be rotated at the same angle, to ensure that the relative position of the measuring point on the coupling is variable, so that the error caused by the unclean surface of the coupling and the axial line of the end face is not perpendicular.
136. What is the premise of the coupling to find the center?
Answer: 1) The axis of the coupling and the rotor coincides. 2) The outer diameter of the journal and the coupling are perfectly round. 3) The end face of the coupling is perpendicular to the axis. 4) Before the coupling is found, the runout of its radial and end face must be measured, and whether the runout of the journal meets the requirements.
137. What are the requirements for coupling assembly?
Answer: Strictly ensure the coaxiality of the two axes, so that there is no unilateral load during operation, so as to maintain balance and reduce vibration.
138. What are the methods for measuring radial displacement and angular displacement of coupling alignment?
Answer: 1) Use support and feeler gauge measurement. 2) Measure with center card and feeler gauge. 3) Measure with center card and dial gauge.
139. How does the safety valve work?
Answer: The safety valve is a kind of valve that automatically opens and closes according to the working pressure of the medium, when the working pressure of the medium exceeds the specified value, the safety valve can automatically open the valve disc and discharge the excess medium (gas). When the pressure returns to normal, the valve disc closes automatically.
140. What are the requirements for valve assembly?
Answer: 1) Assembly conditions: After all valves are cleaned, inspected, repaired or replaced, their dimensional accuracy, mutual position accuracy, finish, material properties and heat treatment and other mechanical properties should meet the technical requirements before assembly.
2) Assembly principle: the general situation is to disassemble the first and then install, after the disassembly of the first installation, to find out the nature of the match, do not knock and beat, the operation is in order, first inside and then outside, from the bottom up, first easy and then difficult, first parts, components, mechanisms, and then the upper cover pressure test.
3) The effect of assembly: proper matching, correct connection, complete valves, bolt tightening, flexible opening and closing, accurate indication, reliable sealing, and adaptable to working conditions.
141. What are the inspection methods for valve quality?
A: 1) Visual inspection. 2) Dimensional inspection. 3) Assembly inspection. 4) Disintegration examination. 5) Pressure test check.
142. How many types of valves are divided into according to their structural characteristics?
Answer: 1) Cut-off type, 2) Gate shape, 3) shape, 4) Butterfly shape, 5) Swing up type, 6) Spool valve shape.
143. What are the basic parameters of the valve?
Answer: 1) the nominal diameter of the valve, 2) the nominal pressure of the valve, 3) the relationship between the working pressure and the working temperature of the valve, 4) the medium used by the valve.
144. What are the characteristics and uses of gate valves?
Answer: 1) Advantages: the sealing performance is better than that of the globe valve, the fluid resistance is small, the opening and closing is more labor-saving, the sealing surface is less eroded by the medium when fully opened, it is not limited by the flow direction of the medium, it has a double flow direction, the structure length is small, and the application range is wide.
2) Disadvantages: high dimensions, a certain space is required for opening, long opening and closing time, the sealing surface is easy to erode and abrasion when opening and closing, and the two sealing pairs bring difficulties to processing and maintenance.
3) Use: Gate valve is generally used in pipelines and equipment with a diameter of DN15-1800mm, and its dosage is very large, mainly for shut-off, and it is not allowed to be used for throttling.
145. What are the functions of valves?
1) opening and closing, 2) regulation, 3) throttling
146. What should be paid attention to when installing a globe valve?
Answer: 1) Due to the asymmetry of the inlet and outlet of the globe valve, the medium should flow through the valve port from bottom to top during installation, that is, low in and high out, so that the valve can be opened with less effort and the packing is not easy to leak. It really plays the role of cutting off, adjusting pressure and flow.
2) If the globe valve is installed in the opposite direction, the inlet pressure will apply pressure to the middle flange base packing part of the valve body, and the design pressure of these two parts of the valve is low, which will cause the leakage of the middle flange and packing of the valve body.
147. What are the general requirements for valve installation?
Answer: 1) Before the valve is installed, the inside of the pipeline should be cleaned to prevent iron oxide filings, welding slag, hard particles or other foreign objects from scratching the sealing surface of the valve. At the same time, carefully check the model and specifications of the valve, and carefully check whether the valve is closed tightly.
2) Pay attention to the installation direction of the directional valve, and do not install it in reverse.
3) Due to the asymmetry of the valve cavity of the globe valve, the fluid flows through the mouth from bottom to top after installation.
4) The gate valve should not be inverted, otherwise the medium will stay in the valve cavity for a long time and it is easy to corrode the valve stem. The open rod gate valve should not be installed at the bottom to avoid rust of the wheel column rod.
5) There are two types of check valves: lifting type and swing type. The lifting check valve can only be installed horizontally, and the swing-open check valve must ensure that its pivot pin is installed horizontally. Swing check valves can be used on horizontal and vertical pipes.
6) Generally, it should be installed in a closed state.
7) When installing or replacing the heavier door, the lifting lock should not be tied to the handwheel or valve stem, but should be tied to the valve body to avoid damage to the handwheel or valve stem and other parts.
8) When the pressure reducing valve is installed, it should be equipped with a shut-off valve and a pressure gauge before and after, and a safety valve should be set behind the valve.
148. What are the general valves with directionality?
Answer: Directional valves generally include globe valves, throttle valves, pressure reducing valves, check valves, etc.
149. What is the strength test process (hydrostatic test) of the valve?
Answer: 1) Drain the internal air after filling the valve with water. 2) The valve is open. Slowly ramp up to test pressure. 4) After reaching the test pressure, the pressure should be maintained for more than 5min, and there should be no leakage at the valve cover of the shell packing.
150. How should the safety valve be transported to the site for installation after the calibration is completed?
Answer: After the safety valve is calibrated, the lead seal should be added, and it should be kept upright during transportation and installation, and it is strictly forbidden to collide with other objects to ensure the calibration accuracy of the safety valve.
151. A Z41H-25, DN80 large gate valve, the bonnet is M16, the packing pressure flange is M12 bolts, what tools need to be prepared for dismantling and overhauling and replacing the packing and bonnet gasket?
Answer: a live wrench 250-300mm, a 24-27 plum wrench, a 17-19 plum wrench, a screwdriver 8 inches, a hammer 1.5P, a plane scraper.
152. What tests should be carried out during valve testing?
A: The hydrostatic strength test is carried out first, and then its air tightness is checked.
153.What does Z44B-16, DN150 mean?
Answer: Z-Gate Valve, 4-Flange Connection, 4-Plane Double Gate, B-Babbitt Seal, 16-Nominal Pressure: 1.6MPa, DN150-Nominal Diameter: 150mm.
154.What does A41T-10, DN100 mean?
Answer: A-safety valve, 4-flange connection, 1-angle type, T-sealing surface is copper mouth, 10-nominal pressure 1.0MPa, DN100-nominal diameter 100mm.
155. What is assembly, and how many steps are there in the general assembly process?
Answer: In the production process, according to the provisions of the drawings and technical requirements, the parts that have passed the inspection are connected in various forms to become components, components, and finally form a complete machine, which is called assembly. The assembly process can generally be divided into component assembly, component assembly and general assembly.
156. How is the assembly work divided?
Answer: For some parts that need to be heated are large and the parts with which they are very small, it is more appropriate to adopt cold installation due to the limitation of heating equipment. There are also parts with special materials or parts that require high precision after assembly, and parts that require very small deformations must be cold assembled.
157. How is the assembly work divided?
Answer: 1) assembly of components, 2) assembly of components, 3) assembly of components, 4) assembly and commissioning.
158. What are the assembly methods for interference connectors?
Answer: 1) Press-in matching method: This method can be divided into two types: hammering method and press press-in method.
2) Thermal expansion matching method: it is the method of hot charging. It is often used in the assembly of interference connections with the largest interference.
3) Cold shrinkage fit method: It is the method of cold installation. It is characterized by a small amount of shrinkage, and is generally used for interference fitting occasions where the amount of interference is small and limited by its method.
4) Hydraulic sleeve method: The method of using hydraulic pressure is hole expansion. Interference fit for shaft shrink assembly.
159. What are thread leads and pitches, and what is their relationship?
Answer: Lead: is the distance that a point on the thread moves along the axis when the point is rotated along the helix. Pitch: is the axial distance between the corresponding points of two adjacent teeth. Relationship: The lead of a single head bolt is equal to the pitch, and the lead of a long thread is equal to the product of the number of heads and the pitch.
160. Why should the threaded connection be prevented from loosening, and what are the commonly used room loosening methods?
Answer: Generally, the threaded connection can meet the self-locking conditions and cannot fall off automatically, but when it is subject to vibration and shock load or temperature changes, the connection may be self-loosening, in order to connect reliably, the design should consider anti-loosening. Method: 1) Friction anti-loosening. 2) Mechanical anti-loosening. 3) Other anti-loosening methods. Such as: pins, nails, pads, caps, etc.
161. What are the four principles that should be followed in the occurrence of equipment accidents?
Answer: 1) The cause of the accident will not be let go until it is investigated. 2) The person responsible for the accident and the public were not spared by the Ministry of Education. 3) Don't let go without precautions. 4) The responsible person has not been punished.
162. What is the content of the four understandings and three meetings of the operator?
Answer: 1) Four understandings: understand the structure of the equipment, understand the performance of the equipment, understand the principle of the equipment, and understand the use of the equipment. 2) Three will: will use, will repair, will troubleshoot
163. What is the "five-character" patrol inspection method for pumps?
Answer: The "five-character" patrol inspection method is listening, touching, measuring, seeing, and smelling.
164. What is the "cross" maintenance method of chemical centrifugal pump?
Answer: The "cross" maintenance operation method is cleaning, sorting, lubrication, tightening, and adjustment
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