Safety News - NH3 Facts

Facts about NH 3

Did You Know?

  • In Alaska , anhydrous ammonia is one of the most prevalent extremely hazardous substances. Ammonia is primarily used as a commercial refrigerant and is found at seafood processing facilities throughout Alaska .
  • Anhydrous ammonia is a colorless gas with a distinctive odor. Ammonia is primarily a respiratory toxicant that can cause lung irritation, and, in higher concentrations, death.
  • The risk to community populations associated with ammonia is substantial. According to the State and Regional Hazards Profile, there are 101 facilities in Alaska that use or store over 600 tons of ammonia at any one time, excluding the urea plant in Kenai. Based on population information, people living near 97 of these facilities could be affected by a release.
  • National studies estimate that approximately 75% of all accidental releases of hazardous chemicals occur at fixed facilities. Anhydrous ammonia is one of the ten hazardous chemicals most commonly involved in a release, AND the second most likely to result in death or human injury due to a release.

What Are the Common Causes of Releases?

Operations and maintenance failures, equipment failures, and process failures are the three leading causes of accidental releases of ammonia. Significantly fewer releases are caused by unauthorized activity, natural events, and fires.

  • Operations and Maintenance Failures include lack of adequate training, standard operating procedures, safety programs, management commitment to safety, and faulty repairs and inattentiveness leading to leaks, overfills, and broken equipment.

•  Equipment Failures include defective equipment design, construction and installation that result in overflowing containers, and leaking piping, valves, and gaskets.

•  Process Failures include pressure, temperature, flow and fluid chemistry changes that result in tank and/or piping ruptures.

Easy Steps to Lessen the Chances of an NH 3 Release

Ammonia refrigeration facilities should be aware of the potential hazards of ammonia releases and of the steps that can be taken to prevent such releases. They should be prepared to respond appropriately if releases do occur. Here are steps that ammonia refrigeration facilities could take to prevent releases and reduce the severity of releases that do occur include:

  • Establish training programs to ensure that the ammonia refrigeration system is operated and maintained by knowledgeable personnel.
  • Remove refrigeration oil from the refrigeration system on a regular basis. Never remove oil directly from the refrigeration system without pumping down and properly isolating that component.
  • Provide barriers to protect refrigeration equipment, i.e., lines, valves, and refrigeration coils, from impact in areas where forklifts are used. Consider starting a forklift driver training program.
  • Periodically inspect all ammonia refrigeration piping for failed insulation/ vapor barrier, rust, and corrosion. Inspect any ammonia refrigeration piping underneath any failed insulation systems for rust and corrosion. Replace all deteriorated refrigeration piping as needed. Protect all un-insulated refrigeration piping from rust and/or corrosion by cleaning, priming, and painting with an appropriate coating.
  • Carry out regular inspections of emergency equipment and keep respirators, including air-purifying and self-contained breathing apparatus (SCBA), and other equipment in good shape; ensure that personnel are trained in proper use of this equipment. For SCBA, it is important to ensure that air is bone dry. For air-purifying respirators, replace cartridges as needed and check expiration dates.
  • Identify the king valve and other emergency isolation valves with a large placard so that emergency responders, in case of an emergency can easily identify them. These valves should be clearly indicated on the piping and instrumentation diagrams (P&IDs) and/or process flow diagrams.
  • Develop written standard operating procedures for removing oil from the oil out pots. Consider developing an in-house checklist to guide mechanics through the procedure.
  • Develop and maintain a written preventive maintenance program and schedule based on the manufacturer's recommendations for all of the refrigeration equipment. The preventive maintenance program should include, but not be limited to:

a) compressors

b) pumps

c) evaporators

d) condensers

e) control valves

f) all electrical safety(s), including

    1)pressure cutouts

    2)temperature cutouts

    3)low oil pressure cutouts

g) ammonia detectors

h) emergency response equipment, including,

   1) air monitoring

   2) SCBA's

   3) level A suit

   4) purifying respirators

•  Properly post ammonia placards (i.e. NFPA 704 NI-I3 diamond) and warning signs in areas where ammonia is being used as a refrigerant or being stored (for example, compressor room doors). Properly identify the chemicals within the piping system(s); label all process piping, i.e. piping containing ammonia, as "AMMONIA." Label must use black letters with yellow background. (This requirement is not the same as the in-house color coding system.)

•  Establish emergency shutdown procedures and instructions on what to do during and after a power failure.

•  Perform vibration testing on compressors. Document and analyze results for trends.

•  Consider using the compressor room ammonia detector to control the ventilation fans.

•  Ensure that good housekeeping procedures are followed in the compressor rooms.

•  Keep an accurate record of the amount of ammonia that is purchased for the initial charge to the refrigeration system(s) and the amount that is replaced. Consider keeping a record of the amount of lubricating oil added to the system and removed from the system.

  • Ensure that refrigeration system lines and valves are adequately identified (e.g., by color coding or labeling) by using an in-house system.
  • Maintain a leak-free ammonia refrigeration system. Investigate all reports of an ammonia odor and repair all leaks immediately. Leak test all piping, valves, seals, flanges, etc., at least four times a year. Some methods which can be used for leak testing are sulfur sticks, litmus paper, or a portable monitor equipped with a flexible probe.

Consider installing ammonia detectors in areas where a substantial leak could occur or if the facility is    not manned 24 hours/day. The ammonia detectors should be monitored by a local alarm company or tied into a call-down system.

Ensure that the ammonia detectors are calibrated regularly against a known standard. Check the operation of ammonia sensors and alarms regularly.

Replace pressure relief valves (PRVs) on a fiveyear schedule; document replacement dates by stamping the replacement date onto each unit's tag.

Replace single PRVs with dual relief valves. A dual relief valve installation consists of one three-way dual shut-off valve with two pressure safety relief valves.

  • Ensure that the ammonia refrigeration system is routinely monitored. Consider using a daily engine room log, recording process parameters (e.g., temperature and pressure levels) and reviewing the log on a regular basis. Consider having the chief engineer and the refrigeration technician sign the daily engine room log. In designing new systems or retrofitting existing systems, consider the use of computer controls to monitor the process parameters.



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