Ammonia is a “natural refrigerant” - a common, naturally occurring compound that breaks down into environmentally neutral hydrogen and nitrogen molecules that do not deplete the ozone layer. It also is energy efficient and effective. For these and other reasons, ammonia increasingly is being used in process cooling applications in place of ozone-depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs).
However, anyone with an ammonia refrigeration system knows that ammonia is not without its drawbacks. According to the U.S. Department of Labor, Occupational Safety and Health Administration (OSHA), ammonia is considered a high health hazard because it is corrosive to the skin, eyes and lungs. Exposure to 300 parts per million (ppm) is immediately dangerous to life and health. Ammonia also is flammable at concentrations of approximately 15 to 28 percent by volume in air. When mixed with lubricating oils, its flammable concentration range is increased. It can explode if it is released in an enclosed space with a source of ignition present, or if a vessel containing anhydrous ammonia is exposed to fire. In short, ammonia is not a substance to treat lightly.
For these reasons and to ensure maximum safety when maintaining ammonia refrigeration systems, some processors prefer to let a professional ammonia-handling firm recover and transfer the ammonia refrigerant rather than handling it in-house. Using an experienced ammonia-handling operation can minimize safety risks and reduce maintenance costs.
Optimizing Recovery and RecyclingWhen an ammonia refrigeration system is pulled offline for maintenance, the ammonia refrigerant must be pumped out and stored until the equipment is ready to be put back into service. The ammonia recovery process can take anywhere from a full day to a week or more when handled in-house. Using an experienced firm with specialized equipment can streamline the recovery time significantly and can provide cost savings.
For example, one company operating a system with a 100,000-lb charge of ammonia and 15 tie-ins had scheduled 15 to 20 hours to recover the ammonia from the -50°F (-46°C) recirculation package and piping alone. The company outsourced the job to NH3 Team Inc., a professional ammonia handler based in Delphos, Ohio, which recovered the ammonia from those components in less than eight hours. The firm also recovered the ammonia from the intermediate stage and high side of the system within the allotted timeframe, which saved the manufacturer a substantial amount of money by reducing downtime and lost production.
Professional handlers also can go beyond simple recovery to optimizing the performance of the ammonia refrigeration system. In one system with a 250,000-lb charge of ammonia, NH3 Team recovered the ammonia in 48 hours. NH3 Team then drained 800 gal of oil from the system after the recovery work was finished, significantly increasing refrigeration system efficiency as well as the plant safety.
During a recovery and maintenance outage on the high side of another system, the freezers were taped off to prevent the doors from being opened. Employees did not heed the tape and were entering and exiting the freezer to perform inventory. In the middle of the project, managers discovered that the freezer temperatures were rising. After determining the cause, the ammonia handler connected a six-cylinder compressor to the low side of the system to pull vapor, reduce the pressure and bring the freezers back to the target temperature. This solution saved the company millions of dollars in product that otherwise would have been wasted.
In another case, testing showed that a system with a 150,000-lb charge of ammonia had 75 percent water in the -50°F side of the system. Water contamination in an industrial ammonia refrigeration system can lower system efficiency and increase the electrical costs required to run the system’s refrigeration compressors. The professional ammonia handler distilled the ammonia using proprietary equipment. After three days of distillation, the saturation test read 3/10 of 1 percent. The ammonia refrigeration system was put back into service, and the manufacturer’s energy costs were reduced substantially.
Limiting Ammonia LiabilitiesWhether you decide to outsource your ammonia recovery project or handle it in-house, a crew of at least two people should be used to minimize safety risks.
Before beginning any work on your ammonia system, remember that oil increases the flammability of ammonia. When ammonia mixed with oil is transferred to a transport, that transport presents an explosion hazard if there is an accident. An ammonia-handling firm can separate the oil from the ammonia and leave the oil on your property to be disposed of properly.
If you’re shutting down a plant, oil can be trapped in the piping after the ammonia is recovered, presenting a fire hazard. Follow through with a refrigeration contractor to alleviate that risk before selling the building or demolishing the refrigeration system.
Finally, if you’re outsourcing the project, be aware of the potential liabilities that can trickle back to the plant and property owner if the ammonia is not transported properly. Manufacturers of nurse wagons (a farming application) recommend that the wagons should be used only for C-grade ammonia, not the R-grade or premium-grade ammonia used in refrigeration systems. An approved ammonia transport should be used to carry R-grade or premium-grade ammonia, and the truck driver should be licensed to transport hazardous materials. Additionally, commercial truck drivers are mandated by the U.S. Department of Transportation to limit their hours of service to a combined total of 14 hours per day on the job site and on the road. A truck leaving your property after the driver has spent all day working on an ammonia recovery project can put you at risk if an accident occurs and enough hours of service were not available.
By understanding the risks and using an experienced ammonia-handling firm, you can ensure that the ammonia in your refrigeration system is handled safely.
NH3 Team Inc., Delphos, Ohio, provides ammonia recovery/recycling and distilling/de-oiling services. For more information, call (800) 643-5495; e-mail firstname.lastname@example.org; or visit www.nh3teaminc.com.