Normally Closed

Written by Jerry Ratzlaff. Posted in Valve

A valve that is designated on the P&IDs as normally closed is one that is closed during normal operating conditions.  A normally closed valve might be one that is used on the bypass of a piece of equipment or an isolation valve for a spare piece of equipment.  Under typical operation, this valve would be closed but during abnormal conditions, such as a maintenance event or shutdown, this valve might be opened up.

  • Abbreviated as NC

Tags: Valve Terminology