IIAR 6 Appendix B Pressure Vessels Checklist | Part 7

Part 7: This is a continuation of our blog series explaining how to perform an IIAR 6 Appendix B inspection of an ammonia pressure vessel.


Item I in the checklist inquires if the pipes are marked as required by IIAR Standard 2. Standard 2 requires piping mains, headers, and branches to be labeled with the following:

  • The word ‘AMMONIA’ should be printed in black letters
  • The physical state abbreviation ‘LIQ’ or ‘VAP’
  • The relative pressure ‘HIGH’ or ‘LOW’
  • An arrow depicting the direction of flow in the pipe.
  • A service abbreviation indicating the purpose of the pipe


Items J and K pertain to valves associated with the vessel. All valves should be visually inspected. Deficiencies that should be recorded include: Corroded or painted stems, missing handwheels, damaged seal caps, or excessive valve body corrosion. In this example, the King Valve has cobwebs on the handwheel which is an indication that the valve has not been exercised or lubricated for some time which should be recorded as a finding.

The vessel must have sufficient instrumentation for monitoring the vessel operating conditions per Item L in the checklist. For most situations, a pressure gauge is sufficient to satisfy this requirement.


The previous blogs in this series are available in the following links. You can watch our free video of how to perform an IIAR 6 Appendix B Pressure Vessel inspection here.

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