Issues with leak testing of startup valves for new installations
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The new unit has been started up; pipeline purging is complete, and all pipelines are properly connected. Now, air tightness is maintained using compressed air and nitrogen. How can one determine whether there is internal leakage in the valves on the pipelines? The valve has been pressurized; the concern is that impurities might have entered during purging and were not removed properly, or that wear may have occurred after several openings and closings.
Then one can only check whether there are other interfaces, apply pressure to one side of the valve while connecting the other side to the atmosphere, and observe the pressure drop on the pressurized side.
This is still easier to detect during the steam purging phase; the processes need to be activated one by one, as the pipelines downstream of valves with internal leaks will heat up. It’s impossible to prevent further internal leakage later on. Once the valve is opened, it can no longer be closed tightly; there’s nothing that can be done about it. Over the years, we have had several instances where internal leakage affected startup or the normal operation of the equipment.
Conduct pipeline pressure testing in segments, and verify each one to ensure it’s OK! ! ! ! ! ! ! ! ! ! !
Make sure to purge the pipeline and then pressurize it as soon as possible; otherwise, things will go badly – the soft sealing surfaces will almost certainly be damaged.
After the purging is complete, close the valve that is to be tested for leaks. Feed gas at a certain pressure before the valve, then install a blind flange; by attaching a pressure gauge to this blind flange, it is possible to determine whether there are internal leaks in the valve.