Where, how and when i must use doub

The double check valves piping setup was to be one of the acceptable mechanism for the system isolations and typically applied in the process system. But through the years, it was gradually replaced in the operation piping system with other more secured mechanism, such as blind, air gapped, etc.. It still uses in the temporary piping clean-up spool in shutdown.
You may want to review the piping systems in the next PHA study of the Ops Unit and discuss the required action to improve the plant safety.

maceca,

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