How is the purging flow rate for process pipelines determined?
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The process pipelines need to be purged with nitrogen before startup. How is the nitrogen flow rate determined?
It’s not based on flow rate; instead, your company’s nitrogen pipeline is connected to the pipe that needs to be purged, and the pressure is increased to that of nitrogen (of course, your pipeline must be able to withstand the highest pressure of nitrogen; if not, low-pressure nitrogen should be used). Then, the release valves and other valves on that pipeline are opened and closed repeatedly until the gas coming out of the pipe no longer stains the white cloth at the exhaust outlet. For a regular flash, high-pressure air should suffice; if necessary, nitrogen can be used for displacement.
There are regulations regarding flow rate; I’m not sure if there are any regulations regarding volume flow!
I’m sorry, I didn’t explain clearly. For purging oxygen pipelines or fuel pipelines, what are the requirements regarding flow rate or velocity?
1. Purging is an operation carried out after the pressure test is completed. The flow rate of the gas used for purging shall be no less than 20 m/s ； Using a high flow rate is suitable for blowing out impurities in the pipeline. 2. If the medium requires degreasing of the pipeline, oil-free and water-free instrument air or nitrogen should be used for purging. If degreasing is not required, a normal air purge can be used, followed by nitrogen purging before starting up.
Compressed air can be used for purging, with a flow rate of not less than 20 m/s. The \"Code for Construction and Acceptance of Industrial Metal Piping Projects\" (GB 50235-97) specifies that nitrogen should be used only during displacement; there is no requirement regarding the flow rate, but the oxygen content at the outlet of the pipeline must be monitored, with it generally not exceeding 1%.
What should be the flow rate for purging with nitrogen? Where are the regulations specified?
In my opinion, when using nitrogen for purging, one simply needs to calculate the volume of the container and pipelines to be purged, multiply it by a safety factor, and then convert that value to the volume of nitrogen at the purging pressure – that amount represents the required quantity of nitrogen.
Compressed air can be used for purging, with a flow rate of not less than 20 m/s. The \"Code for Construction and Acceptance of Industrial Metal Piping Projects\" (GB 50235-97) specifies that nitrogen should be used only during displacement; there is no requirement regarding the flow rate, but the oxygen content at the outlet of the pipeline must be monitored, with it generally not exceeding 1%.
For oil pipelines, cleaning is carried out using cleaning balls – are there any regulations regarding the flow rate?
Piping purging requires no pressure; the purpose is to blow out the impurities inside the pipes. The basis for the inspection is that there are no obvious stains or dirt on the exported wet white cloth!