Q&A on pumps

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What impact does the quality of lubricating oil or grease have on pump bearings? (1) When using lubricating oil, if film or residue is found on the bearing surface, it indicates that the bearing temperature has exceeded the maximum allowable temperature for that lubricant. (2) When using grease, if the grease turns black, it indicates that the bearing is under heavy load. Turning blue indicates that its lubricating capacity has reached its limit. If it turns white, it means the amount used was too large. (3) If the bearing vibrates or is unbalanced, there will be red deposits on the friction surface; these are products of friction corrosion. The presence of metal particles indicates that insufficient amount of lubricant (grease) has been used, resulting in a loss of its lubricating effect. 2. What are the symptoms that occur when a centrifugal pump develops corrosion-related problems? If the materials used in manufacturing the pump are of poor quality, causing certain parts to suffer from pitting corrosion, cavitation corrosion, or intergranular corrosion, this will lead to a decrease in the pump’s flow rate and pressure; in some cases, vibration or noise may also occur. 3. What are the reasons that cause vibration and noise during the operation of a centrifugal pump? (1) The pump shaft and the motor shaft are not aligned properly, the foundation is not strong enough, or there are differences in the thermal expansion and contraction properties of the materials. (2) The pump has a low flow rate; the liquid flow within the pump is uneven, resulting in pressure variations that exert shock forces on the pump. (3) Corrosion of the pump’s rotor or bearings, as well as shaft bending, can cause imbalance. (4) Loose foundation bolts cause vibration in the pump or motor. 4. Why does the flow rate of a centrifugal pump gradually decrease during operation? (1) The check valve at the pump outlet is malfunctioning, resulting in poor flow in the system piping. (2) The components of the pump, such as mouth rings, shaft sleeves, and balancing devices, are corroded. (3) The pump’s speed is insufficient. (4) Clogged impeller or poor fixation to the bearings, etc. 5. Why does a centrifugal pump experience cavitation during operation? (1) The suction pipe is not inserted deep enough into the water tank or is above the water surface. (2) The liquid cannot be pumped up after the impeller is corroded. (3) The viscosity of the medium being transported is too high, the resistance in the suction pipe is large, the liquid temperature is high, and the pressure is low, etc. “The theme of “Questions and Answers about Pumps”: two articles per week. If you like it, please follow! Thank you!