An additional sealing system for shafts, which in the event of main seal failure performs the sealing function until the plant shuts down. Depending on the process in question, the emergency seal is designed for standstill or for operation and standstill.

Function: Given an unacceptably high leakage of the main seal, control equipment and auxiliary systems cause the emergency seal to close and commence operation. An alarm signal is given simultaneously in the control room.

Emergency seal arranged on the atmosphere side, using O-rings with pneumatic or hydraulic actuation (refer also to shut-down seal).
A: connection for monitoring the leakage
B: application of closing pressure