What type of automatic control valve is suitable for liquid chlorine and chlorine gas pipelines?
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On liquid chlorine and chlorine gas pipelines, diaphragm-sealed globe valves are commonly used for manual valves, while ball valves are rarely used! However, when selecting valves for automatic control, globe valves should not be used as cut-off valves; on the other hand, there is concern that automatic control ball valves may not provide adequate sealing, leading to leaks. So I would like to ask whether a bellows-sealed globe valve can be used as the cut-off valve for liquid chlorine pipelines? What is the shut-off time for a pneumatic bellows-sealed globe valve?
Hard-sealed bellows-sealed globe valves should not be able to achieve VI grade, while soft-sealed ones can. For the shutdown time, generally ≤5 seconds should be sufficient, right?
Yes, a soft seal should be used! But there is another issue: the specifications state that cut-off valves should not be used for automatic control, which seems contradictory
For shut-off valves, pressure drop is generally not desired; therefore, standards specify that “globe valves should not be used”. For liquid chlorine, external leakage is the primary concern, so a bellows should be used. If strict internal leakage prevention is required, a soft seal is an option. If that doesn’t work, two stop valves. A standard is a general principle; it is “generally” correct. For example, for a relief switch function valve that is supposed to experience pressure drop, would you still choose a ball valve?
AQ3051-2015: \"For liquid chlorine isolation valves, high-reliability single-seat valves equipped with both diaphragm and packing seals should be used, and the leakage level should be no lower than Class V.\" ”
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