Why is a small valve installed next to the hydrogen flow control valve, and could this pose a risk of leakage?
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I’m seeking advice from those with more experience (as shown in the figure below): (1) Why is a small valve installed next to the thin-film control valve (as indicated by the red arrow in the figure)? (2) Since the medium flowing in the pipeline is hydrogen, does this small valve pose a risk of hydrogen leakage? Is it necessary to cover it with a blind flange? Thank you all for your guidance. The pipe diameter in the above image is 125
(1) The small valve may be used for discharge, sampling, or to cut off flow during maintenance. (2) There is a risk of hydrogen leakage; the small valves should have good sealing properties, and they can be sealed with blind flanges if not in use. .
The small valve is used for pressure relief during the maintenance of control valves, and it is fitted with a wire plug, a pipe cap, or a flange cover.
It should be used for pressure relief during the maintenance of control valves
It’s the first time I’ve seen a small upward-facing valve installed in this location; usually, drain valves are placed at the bottom of the pipeline.
The vent valve is generally used for venting during the maintenance of control valves, and a blind flange needs to be installed when it is not in use.
When the control valve in the middle fails, the inlet and outlet valves must be closed first, after which the valve itself should be opened to allow pressure to be released, so that repairs can be carried out under pressure-free conditions. Under normal circumstances, this valve should be sealed with a plug to prevent leaks.
The third floor is correct: for gaseous media, it is venting, while for liquid media, it is drain condensate. The function of maintaining and adjusting the pressure relief and venting of valves