When is the safety valve inlet check valve used?
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I would like to ask everyone: in some cases, when a shut-off valve is installed at the inlet of a safety valve, it is necessary to place a check valve between the shut-off valve and the safety valve. What is the function of this check valve, and what situations does it serve to monitor? When will it be practical specifically? Thank you.
If this is indeed to be called a check valve, there are two scenarios: First, before removing the safety valve without shutting down the operation, it is necessary to close the upstream manual valve in order to relieve pressure through this valve (this does not apply in cases where toxic substances are involved). If the pressure cannot be fully relieved, it indicates that the upstream manual valve is not sealed properly; in situations where internal leakage is severe, it is not advisable to remove the safety valve. However, there is now online verification, so it’s not necessary to remove it for inspection. Secondly, there is a concern that the valve disc of the upstream valve (gate valve) might fall off; this can be checked by opening it and seeing if there is any medium present.