Does any one here know of an authoritative source (ASME, ISA, NFPA, OSHA, etc..) that gives a definition for the following in one of their standards or codes and the number for that standard or code:

  • LO (Valve Locked Open)
  • LC (valve Locked Closed)
  • CSO (Valve Car Sealed Open)
  • CSC (Valve Car Sealed Closed)

I'm not looking for an explanation, I'm looking for a citable code.


1 Answer 1


That would be Process Industry Practices, Practice Ref. PIC001. Issued 7/15/1998. Appendix A1 contains exactly what you listed.

Edit: I just came across this online: PIC001 Sample, Not for Commercial Use

  • $\begingroup$ I agree that PIC001 contains exactly what I listed, however I am looking for definitions, not what the abbreviations stand for. Thanks for looking though. $\endgroup$
    – Jrican
    Commented Dec 7, 2015 at 17:44

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