The International Institute of Ammonia Refrigeration has released the latest version of IIAR-2, which covers the design of safe closed-circuit ammonia refrigeration systems. IIAR-2 was first released in 1974 and received its last major update in 2015.

“Any change is important for various reasons. The real reason is that sometimes it is a matter of safety, other times it is a matter of clarification,” said Eric Smith, IIAR’s vice president, and technical director. “This revision was the result of opening the entire document up for review and public comment as is required periodically according to IIAR and ANSI procedures. The committee addressed over 400 internal and external comments in painstaking detail, resulting in this latest version. The  volunteer committee members and the public reviewers deserve a great deal of
recognition for their years of hard work on this project.”

Tony Lundell, senior director of standards and safety for IIAR, said the latest version has an updated title: Standard for Design of Safe Closed-Circuit Ammonia Refrigeration Systems.
Previously it was called the Standard for Safe Design of Closed-Circuit Ammonia Refrigeration Systems. IIAR-2 addressed several issues, including a change in ammonia detection and alarms. “Essentially, through risk analysis, research, and a lot of discussion, the committee decided that it was critical for emergency ventilation systems to be more reliable,” Smith
said. “The National Electric Code requires that electrical equipment in a machinery room be either classified as Class I, Division II or that the room be ventilated upon detection of ammonia. Because it is critical that emergency ventilation systems are triggered by ammonia detection, these systems must be reliable and consequently, the requirements for ammonia detection have been
enhanced.” 

Therefore, with some exceptions, machinery rooms are now required to have at least two detectors that are triggered at the same level to activate emergency ventilation.

Another big change is that IIAR has integrated the fire code requirements for emergency pressure control systems. “The good news is that emergency pressure control systems (EPCS) will be
required only when the authority having jurisdiction requires them. An EPCS is presented as one option along with diffusion tanks as a means of mitigating relief valve system releases,” Smith said.
“By including this we are confident that fire codes will defer all ammonia refrigeration requirements to our standard beginning in 2024.”

The standard now permits discharge to the atmosphere, when permitted by the AHJ after an evaluation, or alternatively, providing an EPCS or a dilution tank (rather than both). Prior to this edition of IIAR-2, it was often required to provide both redundant systems.

There were many minor changes made to improve clarity, function, or safety, and users of the standard should review it in its entirety. But additional significant updates to IIAR-2 include:

• New and revised definitions.
• A new requirement is that evaporators and condensers must comply with ANSI B31.5, when not constructed to the Boiler and Pressure Vessel Code.
• Clarifications on the requirements for eyewash/safety showers.
• Changes to machinery-room exhaust and ventilation equipment requirements and proof of operationrequirements.
• New requirements for evaporators concerning design for freeze protection and design for frozen products.
• Revised requirements for equipment enclosures.
• • A new requirement to pressureprotect any equipment with a volume of greater than 0.5 Ft3, regardless of whether it is constructed per the ASME Boiler and Pressure Vessel Code.
• A significant revision of the appendix providing guidance on hydrostatic protection.

New appendices in IIAR-2 include:

• O: Designing to Avoid Component Failure Caused by Abnormal Pressure or Shock.
• P: Removal of Water from a Refrigeration System.
• Q: Guidelines for the Identification of Ammonia Refrigeration Piping and System Components.,