Problems with pipeline airtightness testing
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Beyond visual inspection, are there any more convenient calculation methods to determine the success of a pipeline airtightness test?
Since it is not a strength test but only a leaking test, no conclusions can be drawn through calculations; one can only visually check for leaks, as even the slightest leakage cannot be detected by a pressure gauge. :)
The flange was inspected with soapy water, and a precision pressure gauge was used for monitoring; as required by the standards
The flanges are easy to inspect, but what about tiny holes in the pipeline itself? How can those be detected?
Generally, soap water is applied to the welds and sealing points, along with maintaining pressure for a duration that meets the specified requirements or those outlined in the design documents; there is no room for shortcuts in this process.
The flanges are easy to inspect, but what about tiny holes in the pipeline itself? How can those be detected? Tiny pores in the pipes can cause a drop in pressure, and this can be detected :)
The tiny pores in the pipes are detected during the strength tests prior to ensuring airtightness; when checking for airtightness, it is sufficient to use soapy water to inspect the flange connections and welds – this is what is usually done
No, but it’s not necessary either; the gas changes with temperature anyway, so visual inspection plus soap water is enough
Chlorine can be introduced into the pipeline, and ammonia solution can be used for detection!
The strength of tiny pores in pipes cannot necessarily be detected during the pressure-sealing test; for process pipes, it is necessary to maintain pressure for a longer period of time, usually 2 hours. During pressure holding, check the flange joints and welds using soapy water. If there are no issues with those areas but the pressure still doesn’t hold, then consider whether there is internal leakage in the valve (especially in the drain valve), and only then consider problems with the pipes. When performing pipeline pressure testing, the connected pipes should be disconnected wherever possible to make it easier to locate leaks.
What kind of pipeline? The requirements for airtightness testing vary depending on the type of pipeline. For example, for overhead coal gas pipelines, in addition to reaching the specified pressure, the leakage rate also needs to be taken into account, as shown in the figure below: