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Rev. 2 - Fin al

SPECIAL SAFETY and HEALTH CONSIDERATIONS:

Anhydrous ammonia liquid quickly vaporizes once exposed to normal atmospheric temperature and pressure. The vapor is lighter than air, and will rise in dry air or weather but will be attracted to any moisture on the ground or in the air causing it to become heavier than air. It is highly corrosive to skin and can cause irreversible damage to eyes. Initial contact with ammonia and eyes will cause excessive watering of the eyes to the point of being blinding. Avoid inhalation, skin contact, eye contact, and ingesting. Remove from exposure, if inhaled. Flush skin or eyes with water for at least 15 minutes. Do not induce vomiting if ingested; give 1-2 glasses of milk or water. In all cases, medical aid should be sought. Associates who work with ammonia must not have any physical limitations that interfere with the use of full face respirators. Contact lenses should not be worn by those working with ammonia. Ammonia may ignite in confined areas and can react violently with strong acids. Flames should be extinguished and vapors controlled with a water fog or spray. Do not put water on liquid ammonia, this will cause violent boiling. Additional information on ammonia can be found in the Safety Data Sheets (SDS) for anhydrous ammonia—NH 3

Initial and Normal Start-up:

Verify that the pressure and capacity ratings on relief valve match vessel rating and that three-way isolation valve is in its normal operating position (stem fully counter-clockwise) No start-up is needed for relief valves.

Normal Operation:

The relief valves are always connected to the system and will only open if internal pressures approach the relief setting of the valve. Release may occur within 10 percent% of valve pressure rating. If a valve has released (operated) it must be removed from service and replaced. Do not adjust or repair relief valves.

Normal Shutdown:

The relief valves are always connected to the system and no normal shutdown is required.

Temporary and Emergency Operations:

If any of the dual relief valves activate, find and remedy the cause of high pressure. Then turn stem on three-way valve fully clockwise to remove activated relief valve from service until it can be replaced. If a single relief valve activates, the associated equipment must be isolated from the system and pumped out.

 If relief valve has actuated at a pressure well below its rating or is leaking ammonia around the inlet pipe threads; isolate relief valve from system by changing position of three-way valve. In the case of a single relief valve, the equipment must be isolated from the system and pumped out. Verify that relief valve has been replaced with one of the same pressure rating and capacity and then return three-way valve to its original setting (stem turned fully counter-clockwise) to place new valve in service.

Emergency Shutdown:

Start-up After an Emergency Shutdown

Procedure: Operation, Isolation and Replacement of Pressure Relief Valves Reviewed: 11/01/2023

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