How to calculate the pressure for pipeline purging? ? Help needed
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As the title suggests, the pipeline specifications mention the following regarding pipeline purging: 1) the flow rate should be at least 20 m/s, or 30 m/s; 2) the purging pressure should not exceed the design pressure. So here’s the question: given the diameter of the pipeline, and assuming that the flow rate is at least 20 m/s, how can we determine the purging pressure? ? Are there any relevant calculation formulas? ? Or by experience? How do you proceed? 、
Calculate the Reynolds number based on the flow velocity and the roughness of the pipe, then consult a table to obtain the friction coefficient； The resistance can be calculated by adding the actual length of the pipe to its equivalent length, using a specific formula for pressure drop ； However, in engineering, estimates are usually based on empirical values. Typically, the gas pressure drop is in the range of a few thousand pascals to several tens of thousands of pascals. The liquid has a greater resistance drop, which is due to its high density.
Well, it seems that calculation is also quite troublesome
Is there any experience value, such as what percentage of the design pressure the purging pressure should be? 、
I’m afraid that’s not possible. The design pressure ranges from a few tenths of megapascal to ten or twenty megapascals; purging is used only to remove dirt and debris. There needs to be a specific relationship between the pressure and the design pressure, and it’s not suitable for high-pressure pipelines.
Is it by experience? The safety of the operations must be ensured
Who has the standards and information on this? Please provide it.
To be honest, it all relies on experience; it’s probably not something that requires strict adherence.
It’s hard to say exactly what the purging pressure should be; if the pipes are long, segmental purging can be used
In practice, it’s all based on experience: first warm up the pipes, then gradually open the valve to start blowing. After blowing for a while, reduce the opening of the end purge valve to create pressure buildup, and then open it fully again for further blowing
Is it calculated using PV=NRT?