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I N S T A L L A T I O N , O P E R A T I O N A N D M A I N T E N A N C E M A N U A L
8. The manometric suction head is too high.
9.
Suction pipe or suction strainer is blocked.
10. Insufficient immersion of foot valve or suction pipe during operation of the pump.
11. NPSH available too low.
12. Speed too high.
13. Speed too low.
14. Wrong sense of rotation.
15. Pump doesn't work at the right duty point.
16. Liquid density differs from the calculated liquid density.
17. Liquid viscosity differs from the calculated liquid viscosity.
18. Pumps works when the liquid flow is too low.
19. Wrong pump selection.
20. Obstruction in impeller or pump housing.
21. Obstruction in the piping.
22. Wong installation of the pump unit.
23. Pump and neither motor nor well alignment.
24. Rotating part running out of true.
25. Imbalance in rotating parts (for instance impeller, coupling).
26. Pump shaft is running out of true.
27. Bearing faulty or worn out.
28. Seals rings faulty or worn out.
29. Damaged impeller.
30. Pump shaft or shaft sleeve at shaft packing or running surfaces of the mechanical
seal are worn out or damaged.
31. Worn or dried up shaft packing.
32. Not well packed stuffing box or bad mounting of the mechanical seal.
33. Packing type of the mechanical seal not suitable for the operation liquid or operation
circumstances.
34. Gland of seal cover has been tightened too much or crookedly.
35. No water cooling of stuffing box at high temperatures.
36. The sealing or flushing liquid to the stuffing box or the mechanical seal is polluted.
37. Axial retaining of impeller or pump shaft is defective.
38. The bearings have been mounted wrongly.
39. Too much or too little bearing lubrication.
40. Wrong or polluted lubricant.
41. Impurities in the liquid get into the stuffing box.
42. Too high axial force because worn dorsal blades or excessive inlet pressure.
43. Excessive pressure in packing space due to much play in the smothering bush,
blocked by-pass pipe or worn dorsal blades.
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P a g e
D E C C A N I N D U S T R I E S
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