A large number of facilities require refrigeration. Products as diverse as dairy, pharmaceuticals, food and chemicals often have specific temperature ranges at which they must be kept, and when allowed to warm up beyond those temperatures, they could spoil.
Anhydrous ammonia – pure ammonia without water – is often used in these industrial refrigerated areas. While an effective refrigerant, anhydrous ammonia can be incredibly dangerous to human health if allowed to escape pipes and tanks in which it’s usually confined.
Recently, an ammonia leak sent five employees of a Dallas bakery to the hospital, CBS Dallas/Fort Worth reported. Though the injuries were non-life threatening, the incident required the building to be evacuated, the affected personnel to be brought to the hospital in an ambulance, the HVAC system’s compressor (from which the ammonia was leaking) to be turned off and the fire department to intervene.
This is just one instance where anhydrous ammonia was at the center of a workplace accident. According to the Environmental Protection Agency, 72 percent of chemical accidents in Iowa, Kansas, Missouri and Nebraska involved this chemical. Luckily, the majority of these incidents are preventable when facility managers protect and maintain equipment that uses or is nearby anhydrous ammonia.
Protect anhydrous ammonia-containing equipment
Though the tanks anhydrous ammonia is usually stored in are incredibly sturdy, they’re not infallible. A misguided forklift driver or a runaway hand truck can swiftly cause damage to the metal and cause ammonia to seep out.
To protect ammonia-holding containers, facility managers can install barriers like bollards – thick, metal posts, typically painted yellow, that surround the area and block vehicles from nearing the tank – to keep the vessels safe. Other options include metal grates that go around the sides or curbs that surround the area.
Some facility managers install vertical structures around the ammonia-containing equipment to prevent any products carried on pallets from falling onto them.
Perform maintenance on refrigeration system equipment
When products are kept at a specific temperature range, it’s crucial that refrigeration systems are maintained and inspected regularly. The EPA noted that it’s best to implement a preventative maintenance schedule based on the manufacturer’s recommendation as well as on recognized and generally accepted good engineering practices (RAGAGEPS).
All facilities that have ammonia on the premises – even in storage or quantities less than 10,000 pounds – must adhere to the proper RAGAGEPS. Most people refer to the ANSI/IIAR Standard 7-2013 Developing Operating Procedures for Closed Circuit Ammonia Mechanical Refrigerating Systems.
A few basic practices include:
Draining the oil
Most facilities that have an ammonia refrigeration system also have an oil pot. The oil must be drained periodically to ensure the system is working efficiently. To do this, a worker must release the oil with a self-closing valve. Also called a “deadman valve,” this valve will automatically close if the worker suddenly lets go, preventing unwanted and unsupervised ammonia leakage.
Installing dual relief valves
In the past, single relief valves were commonly found in refrigeration systems. This allows one valve to be serviced while the other maintains pressure in the refrigeration system. Without the dual relief valves, workers have to pump down the equipment before valve maintenance is performed. Relief valves should be replaced every five years.
Monitoring and recording the system’s operations
Operators should keep a daily log on the system’s performance. Every day, preferably around the same time, the operator will take notes on the system’s temperatures, volumes, pressures, lubrication levels and vibrations. Additionally, operators should record startup, shutdown and pump-down processes.
Periodically, the operator should take time to look back at previous entries to determine long-term patterns. If he or she notices changes, like increasing temperatures, lubrication level decreases or rising pressure, it may be time for an inspection.
Be ready for an emergency
Even with an abundance of caution, a small error could lead to an ammonia leak. When this happens, all personnel should be alerted immediately.
Ammonia detection systems must be installed in any room ammonia is used or stored. IIAR 2 requires at least two in every machinery room. The alarms need to be checked, maintained and calibrated periodically to ensure accuracy.
Some facilities invest in ventilation fans they can operate remotely. This allows personnel to simultaneously evacuate buildings and turn on fans.
Installing manual check valves in the ammonia line near the main control valve is another good practice. With this measure in place, employees can isolate problems to prevent further release of ammonia.
Though anhydrous ammonia can greatly benefit a facility by providing an effective refrigeration system, its toxicity presents potential dangers. It’s critical that facility managers invest in protections to prevent leaks and get them under control when they do occur.
By partnering with knowledgeable experts, facilities can ensure features like barriers, alarm systems and warehouse fans are installed properly. Further, they can ensure inspections and maintenance work performed on the refrigeration systems is done correctly. Reach out to Miner to schedule your next routine maintenance check.