Reciprocating Compressors – Slowdown Valve

A blowdown valve relieves trapped pressure when the compressor is shut down due to a malfunction or for maintenance. The flowsheet shows an automatic blowdown valve.

Most operators require automatic blowdown valves so that if the compressor shuts down due to a malfunction, the trapped gas will not become a potential hazard. On some small onshore compressors some operators prefer manual valves to make it easier to restart the compressor. The compressor is only blown down for maintenance.

Often, the blowdown valve is routed to a closed flare system, which services other relief valves in the facility to ensure that all the gas is vented or flared at a safe location. In such instances, a separate manual blowdown valve piped directly to atmosphere, with nothing else tied in, is also needed. After the compressor is shut down and safely blown down through the flare system, the normal blowdown valve must be closed to block any gas that may enter the flare system from other relief valves. The manual blowdown valve to atmosphere protects the operators from small leaks into the compressor during maintenance operations.

Example process flow diagram of reciprocating compressor


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