1. How is the first stage impeller of a multistage centrifugal pump centered with the vane?
Answer:
(1) Put the first stage impeller on the shaft and push it into position, and turn the rotor to the position opposite to the first stage impeller. At this time, the impeller front cover and the inlet guide vane joint remain. The guide vane covers the same gap.
(2) Marking on the shaft based on the end face of the tile, and then assembling. After assembly, the alignment of the first stage impeller can be determined according to the mark on the shaft. If it is not qualified, it can be readjusted.
2. How to overhaul the multistage centrifugal pump?
Answer:
(1) Disassemble the inspection of each component and make a test record of the inspection machine.
(2) Clean and repair the accessories that continue to be used, prepare or process the replacement parts.
(3) Whether the small assembly inspection meets the requirements.
(4) Perform overall assembly work.
(5) The pump is aligned.
(6) Commissioning handover acceptance.
(7) Fill in the inspection record and quality acceptance form carefully.
3. What are the faults of the multistage centrifugal pump?
Answer:
(1) The model of lack of lubricating oil, grease or lubricating oil and grease used does not meet the requirements of the pump.
(2) The process flow is not executed and the operation is incorrect.
(3) The pump is running in the wrong direction.
(4) Improper maintenance.
4. What are the non-human failures of multistage centrifugal pumps?
Answer:
It is not considered that the factor refers to the failure of the pump during operation.
(1) Various gaps change after normal wear.
(2) The strength and rigidity of each component are reduced.
(3) The composition of the conveying medium has changed, and some machine pumps have failed.
5. What are the causes of noise generated by multistage centrifugal pumps?
Answer:
(1) The pump and the prime mover are not aligned.
(2) The rotor and the housing are rubbed.
(3) Bearing wear.
(4) The NPSH of the pump is too small.
(5) The pump is turning incorrectly.
(6) A part of the impeller or the pump casing is embedded with solid foreign matter.
(7) Cavitation, burrs or sharp edges in the flow path cause cavitation.
(8) The impeller is damaged, and the solid debris is blocked by the suction filter.
(9) The suction pool is not arranged correctly.
(10) Loose bolts, etc.
6. What are the inspections of the pump body and the base when the multistage centrifugal pump is installed?
Answer:
(1) The pump body should be free from cracks, and the surface of the liquid flow path is cast smoothly without blisters and pores. The parallelism of the joint surface between the pump sections is 0.1 mm/m, and the joint surface and the flange are free from burrs and collision deformation.
(2) H7/h6 is used for the cooperation between the pump body and the impeller seal ring.
(3) The base and the base surface should be in close contact with each other. The horizontal installation level of the base is 0.05mm/m in the longitudinal direction and 0.10mm/m in the lateral direction.
(4) Pumps with axial expansion slide pins, sliding pin and pin groove should be smooth and burr-free.
(5) When assembling, tighten the total connection screw of the pump body to be symmetrical, and the force should be uniform.
7. What should be paid attention to during the use of multistage centrifugal pump rolling bearings?
Answer:
(1) Rollers and raceways of rolling bearings should have no pits, pitting and rust spots. The cage is intact, the contact is smooth, and there is no noise.
(2) The housing hole tolerance for the rolling bearing outer ring is H7.
(3) The clearance between the bearing gland and the end face of the rolling bearing should be no more than 0.10mm; the clearance between the bearing gland of the expansion side of the shaft and the end face of the rolling bearing should be sufficient to leave sufficient clearance according to the length of the shaft between the bearings and the temperature of the medium.
(4) Disassembly and assembly of rolling bearings should use special disassembly tools or presses. When the bearing is hot-mounted, it can be assembled by heating with a bearing heater or oil of 100~120 degrees Celsius. It is strictly forbidden to use direct flame heating and directly hit the bearing with a hammer.
8. What preparations should be made before the multi-stage centrifugal pump is tested?
Answer:
(1) Install the pressure gauge, vacuum gauge, ammeter and other instruments.
(2) Remove all debris from the pump and clean up the site.
(3) Check the tightening of the pump body and motor base bolts, pump body tension bolts and other connecting bolts.
(4) Add lubricating oil according to the requirements and check whether the cooling water system is unblocked.
(5) Check the shaft seal.
(6) Idle the motor, check the direction of rotation, and install the coupling pin after the error.
9. What are the requirements for multi-stage centrifugal pump test?
Answer:
(1) For two weeks, pay attention to whether there is any noise in the pump and whether the rotation is light. Install the coupling guard immediately after the drive.
(2) Introduce the liquid into the pump and drain the air.
(3) Start according to the installed operating procedures. When the pump is working at full speed and no abnormal conditions are found, the test can be run continuously.
(4) The test run time is 4h or more.
10. What are the requirements for acceptance after the overhaul of the multistage centrifugal pump?
Answer:
(1) The operation is smooth and no noise, and the lubrication and cooling system works normally.
(2) The flow and pressure are stable, and the nameplate capability or the ability to check is achieved.
(3) Under rated head and flow, the motor current does not exceed the rated value.
(4) The temperature of each part is normal.
(5) The vibration of the bearing parts and the casing does not exceed the specified requirements.
(6) There is no leakage at each joint and auxiliary pipeline, and the shaft seal leakage meets the requirements.
(7) The inspection records are complete and accurate, and the test runs are normal, and the inspection and acceptance can be carried out according to the regulations.
