Pneumatically operated valves installed behind check valves on an ejector scrubber.
This is one of the 4 safety protections that avoid that scrubber liquid can be sucked in the direction of the gas lines to the scrubber.
In case of a disturbance, for example a power failure, the pump stops, and these valves open.
As a result an eventual vacuum at the ejectors is broken with gases coming from the gas phase of the scrubber tank.
While an eventual vacuum at the ejectors is broken, the vacuum within systems connected to the scrubber is maintained.