Have you seen a high-flow, high-temperature pump fail to start? It won’t rotate – what should I do?
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This post was last edited by Zhongyuanren on 2015-12-26 at 16:00. Gentlemen, have you ever encountered a situation where a high-flow, high-temperature pump would fail to rotate? It won’t rotate – what should I do? Please speak, thank you
The diesel unit’s turbine disk would not rotate; upon disassembly and inspection, it was found that the balance drum and balance sleeve were stuck together.
Is it in hot standby or cold standby mode?
It won’t rotate anymore; what else can be done? The only option is to take it apart for inspection.
Our company encounters this situation frequently: in a gasification unit, the deoxygenation water pump operates with graywater at a temperature of around 90 degrees. When the pump is in a cold standby state for an extended period, graywater tends to accumulate inside it. To resolve this issue, a winch is used to force the pump shaft to rotate; after a few rotations, the pump can rotate normally again
The temperature of the hot standby can be slightly lower than the operating temperature, to prevent excessive expansion due to high temperatures that could prevent it from rotating. It is also possible to lower the temperature before attempting to turn the shaft. If it cannot be turned, there are several possible reasons: 1, rust and corrosion over time have caused it to stick; 2, the clearance during assembly is insufficient, leading to sticking due to expansion after heating; 3, increased friction in components such as bearings and shaft sleeves
Let’s analyze it: There are several possibilities: 1. The shaft has become rusted and stuck due to daily rotation – rust formation is unlikely in this case； 2. The assembly gap is insufficient, which causes jamming due to expansion after heating; the assembly is done at the factory, so the claim of insufficient gap is not a valid reason. 3. Friction in transmission components such as bearings and bushings increases. Additionally, the pre-heating element is functioning properly; please continue to analyze the causes.
High-flow, high-temperature pumps (1000 M3/h, for fluids at temperatures above 210°C) often fail to rotate. I urge experts to analyze the reasons for this issue and suggest solutions to improve manufacturing standards, operational efficiency, and equipment management practices.
1. The clearance of the mouth ring and other internal clearances are set too small; as a result, there is no clearance after thermal expansion (the manufacturer designed this to ensure the pump’s efficiency, but these clearances can be increased slightly without causing much loss in efficiency). 2. The materials used for the mouth ring, impeller, and pump casing are not well matched to each other, resulting in significant differences in their expansion coefficients. (This method is rather troublesome and not recommended.) 3. The material of the mouth ring is too soft (it is possible to replace it with a mouth ring made of a more suitable material). 4. As for the operational aspect, try to avoid rotating the pump before preheating; rotate it only when the temperature difference between the upper and lower parts of the pump casing is minimal. 5. The preheating circuit of the high-flow pump is not properly configured, resulting in a dead zone during preheating. For high-flow large pumps, it is recommended to use two pre-heating circuits to pre-heat both the top and bottom simultaneously.
Currently, with large-flow pumps, the use of two pre-heating circuits at the front and back of the bottom pump casing along with simultaneous pre-heating at the top still results in the inability to rotate the pump – what is the cause of this problem?