Inspections to Promote a Safe Work Environment

Routine inspections of the compressor(s) in your ammonia refrigeration facility are important for safe and efficient operation. According to IIAR guidelines, at a minimum, the following should be checked: compressor speed, compressor ratio, design discharge pressure and design maximum crankcase/housing pressure. Photo courtesy of Vilter Manufacturing, Cudahy, Wis.
Routine equipment inspections are an important element of any facility's program to ensure the safe and efficient operation of an ammonia refrigeration system. Bulletin No. 109, "Guidelines for: IIAR Minimum Safety Criteria for a Safe Ammonia Refrigeration System," from the International Institute of Ammonia Refrigeration (IIAR), Arlington, Va., is an excellent roadmap for the inspection process. If you use ammonia at your plant and you are not familiar with this bulletin, you should be. Bulletin 109 contains minimum safety criteria and associated data sheets suggested for ammonia refrigeration systems. Compressors are among the components included in the bulletin.

Sometimes, we all need a little refresher, so this installment of "Safe Haven" offers an overview of the key points covered by IIAR's ammonia refrigeration safety inspection checklist for compressors.

All ammonia refrigeration compressors should have a legible manufacturer's nameplate that includes the following:

  • Manufacturer's name.

  • Serial number.

  • Model number.

  • Year of manufacture.

  • Maximum design working pressure.

  • Refrigerant "Ammonia."

  • Rotation speed (maximum rpm).

  • Direction of rotation.

  • Flow direction.

A compressor without a nameplate should not be operated unless the applicable compressor operating limitations have been verified through the identification of the manufacturer and model number of the compressor from the casting numbers.

The compressors should be operated within the limitations specified by the manufacturer. At a minimum, the following should be checked: compressor speed, compressor ratio, design discharge pressure, design maximum crankcase/ housing pressure, and if the compressor is designed for use with ammonia refrigerant.

The compressor drive motor should comply with all local, state and national codes and be in good working order.

Positive-displacement ammonia compressors should be equipped with an internal or external compressor pressure-relief device of adequate size and pressure setting to prevent rupture of the compressor. If the discharge pressure-relief device is vented to atmosphere, it must be piped in accordance with sections 3.11.4.11 and 3.11.4.12 of ANSI/IIAR 2 -1999.

Compressors should be fitted with suction stop valve(s), discharge stop valve(s) and a discharge check valve.

Minimum operable safety controls include a low pressure cutout switch, a high pressure cutout switch and a low oil pressure cutout switch if the compressor uses forced feed lubrication.

You want to inspect for signs of alteration, modification or physical repair that might affect the integrity of the compressor casing. If the casing has been altered, modified or repaired, the casing should have been pressure recertified by the manufacturer or the insurance underwriter and the recertification papers should be maintained on site.

Additionally, the compressor should be fitted with indicating device(s) such that an observer can determine the compressor's suction pressure, discharge pressure and, if the compressor uses forced feed lubrication and discharge temperature, oil pressure.

Finally, each compressor should be ob- served while in operation and checked for excessive vibration, anchor bolt tightness, general cleanliness and other conditions that affect safe operation.

Safety checklists for your compressors as well as pressure vessels, heat exchangers, air-cooling evaporators, evaporative condensers, pumps, piping, ventilation, relief valves and general safety are included in IIAR Bulletin 109. For information on how to get your copy, call (703) 312-4200 or visit www.iiar.org. PCE

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