Ammonia Refrigeration Valve Tags

This is an update to a blog that was originally posted on 10/4/16. You can read the original blog here.

When reviewing an ammonia refrigeration Piping and Instrumentation Diagram (P&ID) and comparing it 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 the current relevant codes and standards that address the topic of valve tagging.

ANSI/IIAR 9-2020 §7.2.9.3 

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 2-2021 §5.14.4 Emergency Shut-off Valve Identification and Tagging.

Valves listed as emergency shut off valves in the system emergency shutdown procedure shall be clearly and uniquely identified at the valves themselves and in the system schematic drawings. 

ANSI/IIAR 2-2021 §13.3.2.8

Valves required for system emergency shutdown procedures shall be readily accessible and identified in accordance with Sections 5.12.5.2, 5.14.1, and 5.14.4. Other valves shall be accessible in accordance with Section 5.12.5.1 

It can be seen that both of the relevant standards (IIAR 9 for existing systems and IIAR 2 for new systems) include the same requirements for labeling emergency shutdown valves. Whether an ammonia refrigeration system is brand new, or 20 years old, the physical shutdown valve and the P&IDs must be clearly and uniquely identified. Here is an example of a P&ID that specifically identifies the king valve: 

Other valves required for system emergency shutdown may include hot gas defrost isolation valves or recirculator pump isolation valves. As indicated in ANSI/IIAR 2-2021 §5.14.4, the emergency shutdown procedures should be referenced when determining which valves would need to be operated in the event of an emergency shutdown.

When installing labels on emergency shutdown valves, it may be prudent to install large placards/signs similar to the labeling of a king valve. Facilities should consider that when ice develops on low-side valves, a small valve tag may be buried under ice and no longer accessible. In an emergency, every second counts. Clearly visible signage will aid emergency responders that are not familiar with your system, and help them more quickly mitigate an ammonia release.