Keeping Ammonia Pure

Impurities can enter the ammonia system:

• While charging the system.
• Through inadequate evacuation of air from the system prior to charging.
• From valve stem packing.
• From piping repairs.
• From piping leaks.
• From the normal breakdown of ammonia.

Potential Hazards:

• Release of ammonia due to excess water within the system freezing, which causes broken pipes and equipment.
• Ineffective refrigeration due to excess oil within the system, causing the system to work harder than necessary, thus stressing the system components.
• Oxygen levels of more than a few ppm in liquid ammonia or a few thousand ppm in gaseous ammonia can promote stress corrosion cracking in steels.
  • This may result in a catastrophic failure of bulk storage vessels.
  • This may result in ammonia weeping from a crack within the refrigeration system.
  • Stress corrosion cracking proceeds more rapidly at high temperatures.

Possible Controls:

• Provide employees information pertaining to the hazards of ammonia. [29 CFR 1910.119(d)(1)]
  • Ensure ammonia being introduced to the system is refrigerant grade.
• Conduct a process hazard analysis. [29 CFR 1910.119(e)]
• Provide operating procedures [29 CFR 1910.119(f)] to ensure proper operation of the system.
  • Follow operating procedures for charging the system to prevent impurities from being introduced.
• Provide training specific to the handling of ammonia. [29 CFR 1910.119(g)]
• Conduct a pre-startup safety review prior to introducing ammonia when the equipment is new or modified significantly enough to require a change in the process safety information. [29 CFR 1910.119(i)]
  • Ensure the effectiveness of air evacuation prior to charging the system.
• Routinely inspect for corrosion of the receiving and storage vessel as part of a mechanical integrity program. [29 CFR 1910.119(j)]
  • Install a non-condensable gas (oil and water) separator (purge units) into the system.
    • Maintain the purge unit according to manufactures specifications.
  • Test and analyze the ammonia periodically for oxygen and water content.
  • Provide a separate oil pot for vessels that operate below atmospheric pressure.
• Establish and implement written procedures to manage changes to equipment, procedures, and to facilities. [29 CFR 1910.119(l)]
• Investigate incidents. [29 CFR 1910.119(m)]
  • Investigate accidents and near misses that could have resulted in a release of ammonia.
• Establish and implement an emergency action plan in case of release. [29 CFR 1910.119(n)]

To learn more about Ammonia Refrigeration visit our Ammonia Refrigeration Safety Online Training web page.