Experts, what procedures should be followed for operating the dry gas seal when the compressor shuts down as part of a shutdown sequence?
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The compressor shuts down in a interlocked manner, the inlet and outlet shut-off valves close, and the pressures of the primary seal gas and the isolation gas decrease. What actions can be taken to maintain the pressure in the balance line?
All compressors have been shut down via interlock; the main priority is to maintain the pressure of the isolation gas. It’s sufficient as long as there is flow in the inlet gases for the primary and secondary seals, and no action is needed regarding the pressure difference in the balance pipes after shutdown.
Dry gas seal systems typically have a supply of nitrogen for startup and for initiating interlock shutdowns; the pressure of this nitrogen is usually higher than the blocking pressure of the dry gas seal. When the compressor shuts down due to interlock, the dry gas seal pressure difference transmitter detects an excessively low pressure difference, and the solenoid valve that controls this nitrogen flow opens automatically to replenish the pressure in a timely manner.
What was said upstairs is correct; having isolation gas is sufficient, as long as oil doesn’t get into the unit. Generally, nitrogen is used, and as long as the pressure meets the requirements, that’s fine.
Dry gas seal systems generally come equipped with a pressurization system, and it is necessary to verify that this system starts automatically as soon as the compressor stops operating