Centrifugal pump maintenance

1, centrifugal pump mechanical seal failure analysis Centrifugal pump shutdown is mainly caused by the failure of the mechanical seal. Mainly due to the failure of the performance of the leak, there are several reasons for leakage: ① static and dynamic ring sealing surface leakage, the main reasons are: flatness of the end surface roughness does not meet the requirements, or scratch the surface; particulate matter between the ends, resulting in two Face can not be the same run; installation is not in place, the way is not correct. ② compensation ring seal leakage, mainly due to: gland deformation, uneven pre-tightening; installation is not correct; seal quality does not meet the standards; seal selection wrong. The actual use of results show that the sealing element failure is the most dynamic parts of the static and static ring end, centrifugal pump seal, static ring end face cracking is a common phenomenon of failure, the main reasons are: ① mounting surface sealing gap is too large, Rinse liquid too late to take away the heat generated by the friction; Rinse liquid leak from the gap in the sealing surface, resulting in overheating and damage. ② vaporization of liquid medium expansion, so that the two ends by the expansion of vaporization and separation, when the two sealing surface force fit, the destruction of the lubricating film resulting in the end surface overheating. ③ liquid medium lubrication is poor, combined with the operating pressure overload, two sealing surface tracking rotation is not synchronized. For example, high-speed pump speed of 20445r / min, the center of the sealing surface diameter of 7cm, pump speed after the line up to 75m / s, when there is a sealing surface can not track the hysteresis rotation, instantaneous sealing surface damage caused by high temperature. ④ seal flushing fluid orifice or filter blockage, resulting in insufficient water, so that machine seal failure. In addition, the sealing surface of the surface of the groove, the end surface of the gap occurs when the gap sealing element failure, the main reasons: ① liquid medium is not clean, hard particles with a little hard, sliding surface with high speed, the end surface of the plan Injury and failure. ② poor coaxial pump drive parts, the pump is turned on each revolution after a week was shaking the friction end, moving the ring trajectory is not the same heart, resulting in end vaporization, overheating wear. ③ frequent occurrence of hydraulic properties of liquid medium caused pump vibration, resulting in seal surface dislocation and failure. Liquid medium on the sealing element corrosion, stress concentration, with hard and soft materials, erosion, auxiliary seal 0-ring, V-ring, concave ring and the liquid medium is not compatible, deformation and so will cause mechanical seal surface damage failure, so Damage to the form of a comprehensive analysis to identify the root causes, to ensure long-term mechanical seal operation. 2, Centrifugal pump requirements after stopping operation ① Centrifugal pump should be shut down after stopping the population of the valve valve, and then turn off the pump after cooling the ancillary system valves. ② high-temperature pump should be stopped according to the provisions of technical documents, after parking should be partial 20 -30 30min half a turn until the pump temperature dropped to 50 ℃ so far. ③ cryogenic pump parking, when no special requirements, the pump should always be filled with liquid; suction valve and the discharge valve should be kept normally open state; the use of double-end mechanical seal of the cryogenic pump, liquid level controller and seal the liquid seal chamber The pump grouting pressure should be maintained. ④ transport easy to crystallize, easy to coagulate, easy precipitation and other media pump, stop the pump should be blocked, and timely flush with water or other media pumps and pipes. ⑤ discharge liquid stored in the pump to prevent corrosion and cracking. 3, the preservation of centrifugal pump ① not yet installed pump unpainted surface should be coated with a layer of suitable anti-rust agent, lubricated bearings should be filled with the appropriate oil, grease-lubricated bearings should only be filled A grease, do not use mixed grease. ② a short time pump clean liquid, flushing, suction lines, discharge lines, pump housing and impeller, side by side net pump housing, suction lines and discharge lines in the flushing fluid. ③ drain the oil bearing box, then add clean oil, thoroughly clean the grease and then fill the new grease. ④ The suction port and exhaust port sealed up, the pump stored in a clean, dry place, to protect the motor windings from damp, with anti-rust liquid and anti-cavitation spray pump housing inside. ⑤ pump shaft rotation once a month to avoid freezing, and lubrication of bearings.

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