IIAR-2: Addressing the Machinery Room

The recent release of IIAR-2 provides an updated standard that clarifies previously cloudy codes and regulations and provides new information that enables facilities to meet the highest safety standards. Specifically where safe machinery room operation is concerned, the standard is critically important to the future of the ammonia refrigeration industry.

There are five key elements that increase safety in a machinery room:

  • construction;
  • ventilation;
  • the emergency detection system;
  • the emergency shutdown system; and
  • the relief systems. I

IAR-2 spells out the specific areas that facilities must address to operate safely, and, in the event of an ammonia leak, how the leak is mitigated.

The road to safety begins with the machinery room’s construction. IIAR defines a machinery room as an enclosed space that is designed specifically to safely house refrigerating equipment. That equipment includes compressors, refrigerant pumps or other refrigerant liquid transfer equipment that raises the pressure of the refrigerant.

The updated standard also requires that the machinery room be separated from the remainder of the building by tight-fitting construction of non-combustible materials with a one-hour fire-resistance rating. The fire rating also applies to doors and windows.

Doors that are used for emergency egress must be identified and equipped with panic hardware.

Piping that penetrates the walls or the ceilings of the machinery room must fit tightly and include fire-preventative material.

Machinery rooms must also be designed so that manually operated valves that are not accessible from floor level can be reached via portable or fixed platforms, ladders, or with a chain-operated system.

“These items were part of the previous standard but some of the provisions weren’t clear. IIAR-2 – 2014 has removed those ambiguities and provided clarification,” says Jack Piho, president of Piho Engineering, a company that assists facilities in understanding and addressing safety codes and regulations.

Ventilation can be the most confusing aspect of designing a machinery room because there have been so many different standards in place, said Piho. “The Fire Marshall or the Fire Chief has the final say, so facilities need to maintain a good working relationship with them.”

Machinery room exhaust to the outdoors must be at least 20 feet from a property line or from openings in the building, measured horizontally, vertically or a combination of both. Emergency exhaust fan motors located in the air stream or inside the machinery room should be totally enclosed but need not be explosion proof. Emergency mechanical ventilation systems should include a minimum of 30 air changes per hour based on the gross machinery room volume.

IIAR-2 has also provided clarification regarding the activation of visual indicators and the audible alarm regarding detection of ammonia concentrations. Detection reaching 25 parts per million (ppm) should activate the indicators and the alarm. Both can be automatically reset if the ammonia concentration drops below 25 ppm. Ammonia concentrations reaching 150 ppm require that the emergency ventilation system starts and continues to operate until it is manually reset by a switch located in the machinery room.

IIAR-2 requires emergency shutdown when detection of ammonia concentrations exceed the lower of the detection’s highest limit or 40,000 ppm. With that, machinery-room refrigerant compressors and pumps and normally closed automatic refrigerant valves must be de-energized. “What’s new is that you now only shut down the rotating refrigerant equipment in the machinery room,” Piho says. “In the old days you would shut down the entire room.”

The new standard requires this shutdown to be automated. Formerly this was not specified.

Finally, the updated standard provides clarification about relief systems. It states “pressure relief devices shall have sufficient mass flow carrying capacity to limit the pressure rise in protected equipment to prevent its catastrophic failure.” Simply, this means . . . protect all equipment.

One provision requires that the risk device capacity factor should be increased to 1.25 when combustible material is stored within 20 feet of a pressure vessel. “The reason is that you could be somewhere else in the facility or even outside where oil drums or other unprotected items are right next to a pressure vessel. In those cases you need to change the calculation method,” Piho says.

The new standard clarifies what a combustible material is and that the concern is about the storage of such materials.

Finally, atmospheric discharge vapor pressure relief devices should send vapor directly outdoors, although exceptions are permitted, and may be required by local jurisdictions.

So how does an existing facility address these new codes and regulations, which in some cases could require costly renovation and design? Facilities will need to evaluate the costs of updating against the risks of not doing so.

Facilities that have not yet been constructed should hire a designer who is familiar with all the current codes and regulations. “The bottom line is that a new facility won’t get a certificate of occupancy that allows it to operate if it doesn’t meet these standards,” Piho says.

Existing facilities that meet the codes on which they were built will typically be grandfathered unless there have been modifications. So why do it? “Owners will – in keeping with internal policy or possibly recommendations of outside resources – choose to update their refrigeration system to meet IIAR-2 and be current, and it’s the right thing to do,” said Piho.