Ammonia Refrigeration Valve Tags
When reviewing an ammonia refrigeration Piping and Instrumentation Diagram (P&ID) and comparing to the actual refrigeration system, I am often surprised at how often valves have not been physically labeled to match the P&ID. One of the purposes of a P&ID is to aid emergency responders who may be asked to close an isolation valve under difficult circumstances (e.g. while wearing an SCBA, Level A suit, etc.). Even a “small” ammonia refrigeration system may have hundreds of valves, that without some type of identification, could easily contribute to a mistake. With that thought in mind, the following list is a summary of relevant codes and standards that address the topic of valve tagging:
2013 CMC §1112.4 Identification
Stop valves shall be identified by tagging in accordance with the reference standard for identification. A valve chart shall be mounted under glass at an approved location near the principal entrance to the machinery room.
2015 UMC §1110.5 Identification.
Stop valves shall be identified by tagging in accordance with the reference standard for identification. A valve chart shall be mounted under glass at an approved location near the principal entrance to a refrigeration machinery room.
2015 IMC §1107.8.3 Identification
Stop valves shall be identified where their intended purpose is not obvious. Numbers shall not be used to label the valves, unless a key to the numbers is located near the valves.
ANSI/IIAR 2-2014 §5.14.3 Emergency Shutdown Valve Identification and Tagging.
Valves required for emergency shutdown of the system shall be clearly and uniquely identified at the valve itself and in the system schematic drawings.
ANSI/IIAR 2-2014 §13.3.7
Valves required for system emergency shutdown procedures shall be readily accessible and identified in accordance with Sections 5.14.3 and 6.3.3.2. Other valves shall be accessible in accordance with Section 6.3.3.1 if installed in a machinery room.
IIAR Bulletin No. 109 §4.10.3
The main shut-off valve(s) (king valve(s)); hot gas defrost line main shut-off valve; and NH3 pump liquid main shut-off valve(s) and/or disconnects; of the ammonia system should be readily accessible and identified with a prominent sign having letters sufficiently large to be easily read.
ANSI/ASHRAE 15-2013 §9.12.6
Stop valves shall be suitably labeled if the components to and from which the valve regulates flow are not in view at the valve location. Valves or piping adjacent to the valves shall be identified in accordance with ANSI A13.1. When numbers are used to label the valves, there shall be a key to the numbers located within sight of the valves with letters at least 0.5 in. (12.7 mm) high.
While the codes and standards listed above do not align with each other in every aspect of valve tagging, they serve to demonstrate that the valves (particularly main shut off valves) associated with an ammonia refrigeration system must be identified in such a way to make the valve function known.
Has this changed at all since 2016? Currently evaluating tagging oil valves on the compressors.
The main change is that UMC, CMC, IMC, and ASHRAE all directly reference IIAR 2 now. So the IIAR 2 reference has not changed, but the other codes simply point to IIAR for compliance.
We are currently reviewing our P&IDs and noticed that the check valves do not have a tag on the physical valve or on the P&ID. Are check valves included to have valve tags?
Since a check valve is a type of valve, it should be treated the same as other valve types (globe, expansion, ball, etc.) relative to tagging. This applies to both your P&IDs and physical tags.