【Daily Question No. 342】December 14, 2018
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【Daily Question No. 342】December 14, 2018: Briefly explain why a centrifugal pump should not operate for too long with the outlet valve closed Because the outlet valve remains closed for too long, the impeller keeps rotating, causing the liquid inside the pump to be continuously stirred and rubbed, which generates high temperatures and leads to the deformation or damage of some components. (Unless otherwise specified, all questions and answers are based on hydrogenation units.) ) Correct: 3 wealth, Incorrect: 1 wealth ； Mass posting of posts – rated based on the lowest score ； Replies that are unrelated to the answer are considered spam and will be deleted immediately. For management purposes, if you need to view content from a few days ago, please go to https://bbs.hcbbs.com/home.php?mod=space&uid=3862647&do=thread&view=me&from=space through the summary post below
All operating equipment must function under its designed conditions in order to extend its service life and maintenance intervals； When the outlet valve is closed, the outlet pressure rises and the water flow rate decreases; the motor has to do a large amount of unnecessary work, which leads to an increase in current and higher heating of the coils. Prolonged operation can damage the pump’s sealing. So it has no advantages at all and only disadvantages.
Because the outlet valve remains closed for too long, the impeller keeps rotating, causing the liquid inside the pump to be continuously stirred and rubbed, which generates high temperatures and leads to the deformation or damage of some components.
1. Sudden increase in pump outlet pressure； 2. The pump body temperature rises.
It will cause continuous stirring and heating of the medium inside the pump, leading to cavitation in the pump； The pump is operating away from its set point, resulting in excessive vibration ； The axial and radial forces are high; excessive outlet pressure can cause damage to the outlet pipelines and valves ；
After a centrifugal pump operates with the outlet valve closed, the liquid is rapidly agitated by the impeller, causing it to vaporize quickly; as a result, areas with narrow gaps – such as those around the sealing rings – do not receive lubrication or cooling, which can easily lead to shaft seizure and serious accidents.
If it remains shut down for too long, the liquid inside the pump not only experiences increased pressure but also heats up and vaporizes, generating shock forces that can damage the impeller, the pump casing, or the shaft seal mechanism
When a centrifugal pump is in operation, the outlet valve can be closed for a short period of time, but the closing time should not be too long. If it is closed for too long, the liquid inside the pump will experience an increase in pressure, and it will also heat up and vaporize, generating shock forces that can damage the impeller, the pump casing, or the shaft seal mechanism.
Leaving the outlet valve closed for too long can cause the pressure inside the centrifugal pump to rise; if this pressure becomes too high over an extended period, it can lead to the pump exploding
Because the outlet valve remains closed for too long, the impeller keeps rotating, causing the liquid inside the pump to be continuously stirred and rubbed, which generates high temperatures and leads to the deformation or damage of some components.