To be used to maintain the vacuum upstream of the first stage ejector rather than allowing the pressure to rise to atmospheric pressure. Note an isolation valve has to be present at suction. In this case the isolation valves should be closed in the following order.
- Close first stage (Y stage) suction valve.
- Close first stage (Y stage) motive inlet valve.
- Close first stage (Y stage) discharge valve.
- Close second stage (Z stage) suction valve.
- Close second stage (Z stage) motive inlet valve. Note: If more than two stages are present STOP HERE and continue to repeat steps, 3, 4, and 5 before proceeding to step 6
- Close second stage (Z stage) discharge valve (when present).
Note: If the system contains an isolating valve at the first stage suction only, the procedure would be to close this valve and then either shut off the motive to all ejectors at once or shut them off by stages, starting at the first stage. When all motive valves have been shut off, the cooling water may be turned off also. If the unit is going to be shut down for a short period of time to service the ejectors or for some other reason, it is not necessary to shut off the cooling water. Energy savings should be considered when making this decision. If the unit is going to be down and freezing of the cooling water is possible, then measures must be taken to prevent freezing or the unit drained as much as possible to prevent damage.