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 time is called power.

3. What is effective power?

In addition to the energy loss and consumption of the machine itself, the actual power of the liquid obtained by the pump per unit time is called 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 delivered by the motor to the pump always greater than the effective power of the pump?

Answer: 1). During the operation of the centrifugal pump, a part of the high-pressure liquid in the pump will flow back to the inlet of the pump, or even leak to the outside of the pump, so some energy must be lost; 2). When the liquid flows through the impeller and the pump casing , The change of flow direction and speed, as well as the mutual impact between fluids also consume a part of energy; 3). The mechanical friction between the pump shaft and the bearing and shaft seal also consumes a part of energy; therefore, the power transmitted by the motor to the shaft 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 the pump? What is the symbol?

Flow rate refers to the amount of liquid (volume or mass) flowing through a certain section of the pipe per unit time. The flow rate of the pump is represented by "Q".

8. What is the head of the pump? What is the symbol?

Answer: The head refers to the increase in energy obtained per unit weight of fluid. The pump head is represented by "H".

9. What are the characteristics of chemical pumps?

Answer: 1). Can adapt to chemical process requirements; 2). Corrosion resistance; 3). High temperature and low temperature resistance; 4) Wear resistance and erosion resistance; 5) Reliable operation; 6) No leakage or less leakage; 7) Can be transported Critical state liquid; 8) Has anti-cavitation performance

10. How many types of commonly used mechanical pumps are classified according to their working principles?

Answer: 1) Vane pump. When the pump shaft rotates, it drives various impeller blades to give the liquid centrifugal force or axial force, and transport the liquid to the pipeline or container, such as centrifugal pump, vortex pump, mixed flow pump, and axial flow pump. 2) Positive displacement pump. Pumps that use continuous changes in the volume of the pump cylinder to deliver liquids, such as reciprocating pumps, piston pumps, gear pumps, and screw pumps; 3) other types of pumps. Such as electromagnetic pumps that use electromagnetic to transport liquid electrical conductors; pumps that use fluid energy to transport liquids, such as jet pumps, air lifts, etc.

11. What should be done before chemical pump maintenance?

Answer: 1) Before overhauling machinery and equipment, stop, cool down, relieve pressure, and cut off the power supply; 2) For machinery and equipment with flammable, explosive, toxic, and corrosive media, it must be cleaned, neutralized and replaced before overhaul Construction can only be carried out after passing the analysis and testing; 3) For maintenance of flammable, explosive, toxic, corrosive media or steam equipment, machinery, and pipelines, the material outlet and inlet valves must be cut off, and blind plates must be installed.

12. What process conditions should be met before chemical pump maintenance?

Answer: 1) Stop; 2) Cool down; 3) Relieve pressure; 4) Cut off the power; 5) Replace

13. What is the general mechanical disassembly principle?

Answer: Under normal circumstances, you should firstly disassemble the parts from outside, then inside, up and down, and disassemble the whole parts as much as possible.

14. What is the power loss in the centrifugal pump?

Answer: There are three kinds of losses: hydraulic loss, volume loss, and mechanical loss. 1) Hydraulic loss: When fluid flows in the pump body, if the flow channel is smooth, the resistance will be smaller, and the flow channel will be rough, and the resistance will be larger. When the impeller or water flow comes out of the impeller, collisions and vortices will cause losses. The above two losses are called hydraulic losses. 2) Volume loss: the impeller is rotating, and the pump body is static fluid in the gap between the impeller and the pump body, a small part of the fluid flows back to the inlet of the impeller; in addition, a part of the fluid flows back to the inlet of the impeller from the balance hole, or Leakage from the shaft seal. If it is a multi-stage pump, a part of the balance plate will also leak. These losses are called volume losses; 3) Mechanical losses: When the shaft rotates, friction occurs with bearings, packing, etc., the impeller rotates in the pump body, and the front and rear cover plates of the impeller have friction with the fluid, which consumes part of the power. Loss caused by friction always becomes mechanical loss.

15. In production practice, what is the basis for the rotor to find balance?

Answer: According to different speeds and structures, static balance method or dynamic balance method can be used. The static balance of the rotating body can be solved by the static balance method. Static balance can only balance the unbalance of the rotating center of gravity (that is, eliminate the torque), but cannot eliminate the unbalanced couple. Therefore, static balance is generally only suitable for disk-shaped rotating bodies with a relatively small diameter. For a rotating body with a relatively large diameter, the dynamic balance problem is often more common and prominent, so dynamic balance treatment must be performed.

16. What is balance? How many types of balance are there?

Answer: 1) The work to eliminate the unbalance of rotating parts or components is called balance; 2) Balance can be divided into static balance and dynamic balance.

17. What is static balance?

Answer: In some special tooling, the front position of the unbalance of the rotating part is measured without rotation, and the position and size of the balance force should be determined at the same time. This method of finding balance is called static balance.

18. What is dynamic balance?

Answer: When the parts are rotating through the components, not only the centrifugal force generated by the partial weight must be balanced, but also the balance of the couple moment composed of the centrifugal force is called dynamic balance. Dynamic balancing is generally used for parts with high speed, large diameter, and particularly strict requirements for working accuracy, and precise dynamic balancing must be done.

19. When doing static balancing of rotating parts, how to determine the weighted 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 centerline (due to frictional resistance), at this time it is at the lowest part Mark the point with white chalk, and then let the part roll freely. The last roll is done in the counterclockwise direction, then the center of gravity of the balanced part must be on the left side of the vertical centerline. Also use white chalk to make a mark, then The center of gravity of the two records is the orientation.

20. When doing static balance of rotating parts, how to determine the size of the balance weight?

Answer: First, turn the weight of the part to the horizontal position, and add appropriate weight to the largest circle at the opposite symmetrical position. This should be taken into account when selecting the appropriate weight. Whether the weight can be weighted or reduced in the future, and after the appropriate weight is added, the position should be kept horizontal or slightly swing, and then the part should be reversed 180 degrees to make it Keep the horizontal position, repeat several times, after the proper weight is determined unchanged, remove the proper weight and weigh it, which determines the gravity of the balance weight.

21. What are the types of mechanical rotor imbalance?

Answer: Static imbalance, dynamic imbalance and mixed imbalance.

22. How to measure the bending of the pump shaft?

Answer: After the shaft is bent, it will cause the unbalance of the rotor and the wear of the dynamic and static parts. Put small bearings on the V-shaped iron and large bearings on the roller bracket. The V-shaped iron or bracket should be stable, and then the dial indicator Point to the shaft, and then slowly rotate the pump shaft. If it is bent, the micrometer will have the maximum and minimum readings per revolution. The difference between the two readings indicates the maximum radial runout of the shaft bending, also known as shaking degree. The shaft curvature is one-half of the sway. Generally, the radial runout of the shaft is no more than 0.05mm in the middle and 0.02mm at both ends.

23. What are the three main causes of mechanical vibration?

Answer: 1) Structure: caused by manufacturing design defects; 2) Installation: mainly caused by improper assembly and overhaul assembly; 3) Operation: due to improper operation, mechanical damage or excessive wear.

24. Why is the rotor misalignment an important reason for abnormal rotor vibration and early bearing damage?

Answer: Due to the installation error between the rotors, the manufacturing of the rotor, the deformation after load, the change of the ambient temperature and other factors, it may cause poor alignment, poor rotor alignment of the shaft system, due to the change of the coupling force, Changing the actual working position of the rotor journal and the bearing not only changes the working state of the bearing, but also reduces the natural frequency of the rotor shaft system. Therefore, the rotor misalignment is an important cause of abnormal rotor vibration and early bearing damage.

25. What is the standard for measuring and reviewing the ellipticity and taper of the journal?

Answer: The ellipticity and taper of the shaft diameter of the sliding bearing should meet the technical requirements, and generally should not be greater than one thousandth of the diameter. The ellipticity and taper of the shaft diameter of the rolling bearing shall not be greater than 0.05mm.

26. What should be paid attention to when assembling chemical pump?

Answer: 1) Whether the pump shaft is bent or deformed; 2) Whether the balance of the rotor meets the standard; 3) The gap between the impeller and the pump casing; 4) Whether the compression of the mechanical seal buffer compensation mechanism meets the requirements; 5) The pump rotor and Concentricity of the volute; 6) Whether the center line of the pump impeller flow channel and the center line of the volute flow channel are aligned; 7) the gap adjustment between the bearing and the end cover; 8) the gap adjustment of the sealing part; 9) the transmission system motor Whether the assembly of the speed changer (increasing or decelerating) conforms to the standard; 10) Coaxiality alignment of the coupling; 11) Whether the gap between the mouth ring conforms to the standard; 12) Whether the tightening force of the connecting bolts of each part is appropriate.

27. What is the purpose of pump maintenance? What are the requirements?

Answer: Purpose: To eliminate the problems that exist after long-term operation by overhauling the pump. The requirements are as follows: 1) Eliminate and adjust the large gaps in the pump due to wear and corrosion; 2) Eliminate dirt, dirt, and rust in the pump; 3) Repair or replace non-compliant or defective parts; 4 ) The rotor balance test is qualified; 5) The coaxiality between the pump and the driving machine is checked and meets the standard; 6) The test run is qualified and the data is complete, meeting the technological production requirements.

28. What is the reason for the excessive power consumption of the pump?

Answer: 1) The total head does not match the pump head; 2) The density and viscosity of the medium do not match 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) The impeller port Ring wear; 6) Improper installation of seal or mechanical seal.

29. What are the reasons for the imbalance of the rotor?

Answer: 1) Errors in manufacturing: uneven material density, different axis degrees, out-of-roundness, uneven heat treatment; 2) incorrect assembly: the center line of the assembly part is different from the axis; 3) the rotor is deformed : Uneven wear and deformation of the shaft under operation and temperature.

30. What is a dynamic unbalanced rotor?

Answer: There are rotors that are equal in size and opposite in direction, and the unbalanced mass points are integrated into two couples that are not on a straight line in one day.

31. How to prevent evacuation and cavitation during operation?

Answer: Pump down: There are gas and liquid in the pump, the pump cannot work, and the flow and pressure tend to zero. Cavitation: It occurs in the pump during operation and comes from the medium in the pump. The flow and pressure change and drop, resulting in hydraulic shock. Generally, pump evacuation refers to a kind of cavitation phenomenon that occurs in the pump. The evacuation caused by the inhalation of gas due to the leakage of the installation technology pipeline is not common, and most of them are caused by operation and process changes. In the operation process, we should start with stable process operating conditions. The operating temperature should be lower limit, and the pressure should be lower limit. In order to avoid or control the occurrence of cavitation, the flow rate of the pump should be moderate during operation to minimize the pressure and temperature. The change. The suction pipeline of the pump should be prevented from remaining gas, and the inlet of the standby pump whose inlet pressure is negative should be closed.

32. What is dynamic fit and static fit? 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, shaft pair The hole can do relative movement; static fit: the shaft and the hole do not move relative to each other.

33. What are the four basic requirements for equipment maintenance?

Answer: neat, clean, lubricated and safe

34. What is the working principle of the labyrinth seal?

Answer: Labyrinth seal: There are a number of ring-shaped sealing teeth arranged in sequence. A series of throttling gaps and expansion spaces are formed between the teeth and the rotor. The fluid passes through many tortuous channels and generates a lot of resistance after multiple throttling. Make the fluid difficult to leak and achieve the purpose of sealing.

35. What is the interchangeability of parts?

What is the main function? Answer: 1) The parts can be interchanged and used, and can meet the various index requirements of the original parts, which is called the interchangeability of the parts. 2) Mainly play a role in facilitating maintenance, reducing maintenance time, improving equipment utilization and working efficiency.

36. What is a power pump?

Answer: The power pump continuously transfers energy to the liquid to be transported, so that both the speed kinetic energy and the pressure energy potential energy are increased, mainly because the speed increases, and then the speed is reduced, so that most of the kinetic energy is converted into pressure energy. Use the increased pressure of the liquid to be transported, such as: 1) vane pumps, which include centrifugal pumps, mixed flow pumps, axial flow pumps, vortex pumps, etc.; 2) jet pumps, including gas jet pumps, liquid jet pumps, etc. .

37. What is a positive displacement pump?

Answer: In the process of periodically changing the volume of the pump cavity, the positive displacement pump transfers the capacity to the liquid to be conveyed with the periodic change of action and displacement, so that the pressure can be directly increased to the required pressure value to realize delivery, such as : 1) Reciprocating pumps, including piston pumps, plunger pumps, diaphragm pumps, extrusion pumps, etc.; 2) Rotor pumps, including gear pumps, screw pumps, Roots pumps, rotary piston pumps, sliding vane pumps, crankshaft pumps, and Rotor pump, peristaltic pump, etc.

38. What are the main performance parameters of the pump?

Answer: It mainly includes: flow, head, cavitation margin, speed, power and efficiency.

39. Why should the spare equipment be cranked regularly? What should be paid attention to when cranking?

Answer: 1) For the regular cranking of the spare equipment, one is to check whether the equipment is running flexibly and whether there is jamming; the other is to prevent the bearing from bending and deforming, which really plays a backup role. 2) Attention should be paid when cranking: First, the stop position of the rotor after the cranking is at an angle of 180 degrees to the original position; second, the pump that is lubricated by the oil should be lubricated after the cranking to prevent damage to the bearings.

40. What is the harm to the pump if the current exceeds the rated current?

Answer: The rated current is the current that the motor normally does work under the condition of rated voltage and rated power. If the rated current is exceeded, the motor is likely to overheat and the relay protection device will act, causing the pump to stop. For example, the relay protection device does not operate or does not operate. It is easy to burn the motor and damage the pump.

41. What are the main contents of the machine pump inspection?

Answer: 1) Check whether the indicated values of the pressure gauge and ammeter are in the specified area and remain stable; 2) Check whether the running sound is normal and there is no noise; 3) Whether the temperature of the bearing, motor, etc. is normal (not exceeding 60 degrees); 4 1) Check whether the cooling water is unblocked, the packing pump and the mechanical seal are leaking, if 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 the oil level is normal;

42. When the maintenance personnel arrive on duty for maintenance, what should the equipment operators do?

Answer: 1) Check whether the maintenance work ticket is consistent with the actual equipment location number to be overhauled; 2) Contact the shift chief and find an electrician in the special area to cut off the power; 3) Provide the maintenance personnel with equipment damage and specific parts of the maintenance; 4) Cooperate on site Overhaul and supervise the quality of overhaul; 5) After the overhaul is completed, contact for power transmission and test run; 6) After the operation is normal, report to the shift leader and make records at the same time.

43. What is the function of the pump inlet and outlet valves?

Answer: 1) The pump inlet valve is a component that isolates or cuts off the slurry pump from the system during maintenance.

44. According to what seal should be used for chemical production pumps?

Answer: According to the process conditions, working pressure, and medium corrosion conditions, the rotation speed is selected.

45. What are the types of flat gasket seals?

Answer: 1) Non-metallic gasket seal; 2) Non-metallic and metal composite gasket seal; 3) Metallic gasket seal.

46. What are the main reasons for gasket leakage?

Answer: 1) Leakage caused by design; a improper selection of flange and flange sealing surface form; b improper selection of gaskets; c improper selection of flange and bolt materials; 2) leakage caused by manufacturing, installation and operation; a flange The processing accuracy of the gasket and the gasket does not meet the technical requirements; b. Improper operation when tightening the bolts, causing the gasket to deviate; c. The flange sealing surface is clean and contains impurities.

47. What is a mechanical seal?

Answer: Mechanical seal is also called end face seal. It is composed of at least one pair of end faces perpendicular to the axis of rotation. Under the action of fluid pressure and compensation mechanism, the two end faces closely fit and slide relative to each other to form a device to prevent fluid leakage.

48. How many types of seals are commonly used in pumps?

Answer: There are two types, dynamic seal and static seal.

49. What are the main causes of mechanical seal leakage?

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, causing the sealing end face to crack, deform, and break. 2) Several auxiliary sealing rings have defects or defects caused by improper assembly, and the selection of auxiliary sealing rings is not suitable for the working condition medium. 3) The spring preload is insufficient or after a long time of operation, breakage, corrosion, relaxation, coking, and long-term accumulation of suspended particles or crystals of the working medium are blocked in the spring gap, causing the spring to fail and the compensation seal ring cannot float , Leakage occurs; 4) Due to the excessive deviation of the verticality between the dynamic and static ring seal end faces and the shaft center line, the seal end faces are not tightly bonded and cause leakage; 5) Because the shaft has a large axial movement, it is matched with the fittings related to the seal Or the quality is not good, it is easy to cause leakage.

50. According to what material to choose mechanical seal friction pair?

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 during startup or when the liquid film is broken.