Regarding the definition of \"pressure holding\"
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In the pump industry, the term \"pressure holding\" is rarely heard; one can roughly understand what it means, but not exactly. Could those who are familiar with this term explain its official definition and the reasons behind it? Thank you very much
The client needs to specify the exact field of application and scope before a response can be given. Pressure retention – no release of air, no pressure reduction, or exceeding the operating (control) pressure. By \"holding pressure in the pipeline,\" I understand it as maintaining a certain pressure and, after one cycle, checking for deformation and leakage in the pipeline. At this time, the pressure is generally the test pressure.
This post was last edited by ylb913 on 2015-7-3 at 16:24. Stagnation in the system usually occurs because of high pressure downstream (this is often caused by non-condensable gases; releasing such gases, reducing temperature, or switching to another tank can resolve the issue), or because the flow rate is too high while the pipelines are too narrow, resulting in insufficient delivery of material upstream. There are also some cases of pressure buildup in such devices; for example, the pump is located behind a device filled with liquid, and when the pump starts operating the outlet valve of that device remains closed. Another example: material is being transported normally, but later it needs to be directed into another tank – yet they close the valve first and then open it, which causes our safety valves to activate (this kind of thing happened frequently in previous years, and they never learned from their mistakes). There is also the case in summer, when a section of a gasoline or liquefied gas pipeline is not in use with valves closed at both ends; as a result of rising temperatures or exposure to sunlight, the gas inside vaporizes and its pressure increases, which can cause the gaskets to fail. The same phenomenon occurs in a section of pipeline filled with liquid when heating is applied. Finally, the backflow system or pipelines become blocked due to reasons such as impurity deposition, crystallization, and condensation, which leads to an increase in pressure ahead.
“\"Pressure buildup\" literally means that the pressure cannot be released and cannot escape. In some cases, \"pressure retention\" is normal, such as during pressure testing. In some cases, \"pressure buildup\" is not appropriate; for example, when a smooth pipeline gets blocked, pressure will build up within it. My personal understanding....
My understanding is to seal one end of the pipeline and apply pressure while maintaining it at a level higher than the normal operating pressure (but not exceeding the maximum allowable pressure)
Start the pump and build up pressure. When starting a centrifugal pump, the outlet valve must be closed (this is what is commonly referred to as building pressure). Why? Because the shaft power of a centrifugal pump increases as the flow rate increases. When the flow rate is zero, the shaft power is at its minimum; therefore, by closing the outlet valve and starting the motor, it is possible to prevent excessive starting current from damaging the motor