The risks involved with ammonia refrigeration are substantially reduced by EPA’s Risk Management program (RMP) and preventive maintenance. Part of that process is clear labeling of incorporated pipes and equipment. As the accepted industry experts in this field, the IIAR maintains a code of recommendations for refrigeration equipment labeling- Manuchehr Mehdizadeh, BSME Project Advisor-All aspect of Cold Chain Industries-USA
Ammonia Refrigeration Basics
The refrigeration systems use basic physics to transfer heat energy out of one area and into another, leaving the first area cooler than it was before. Indoor ice hockey rinks and grocery store freezer sections use the same process on a larger scale. Massive industrial facilities like petrochemical refineries and food processing plants rely on large-scale refrigeration systems for their day-to-day operations.
The most common type of industrial refrigerating system is a vapor-compression refrigeration. This approach uses a fluid called a refrigerant as the means of moving heat around. Most of the time, the refrigerant is a vapor. At one point in the system, it’s compressed to become a liquid; later, it’s allowed to expand and vaporize again. The process repeats on a cycle. Each time the refrigerant vaporizes, it absorbs heat energy from its surroundings, and each time it condenses, it releases that heat to its new location.
The physical properties of the refrigerant determine the pressure and temperature ranges of the system, along with the rate of cycling required for a given cooling effect. In turn, those details determine the efficiency of the refrigeration system as a whole. The choice of refrigerant is important, and many synthetic materials have been created for the purpose. In the past many kind of chlorofluorocarbons (CFCs) gases such as Freon R-12/R-22 etc were developed and widely used during the 20th century, until their destructive impact on the environment was discovered.
Why Ammonia Refrigeration?
Ammonia is a natural choice (with ODP=0 & GWP=0) of refrigerant on large cold chain industries. Following reasons areconsidered for choosing ammonia as a refrigerant:
- Ammonia’s physical properties make it effective and efficient for large systems.
- It breaks down quickly in the environment, minimizing potential environmental impact.
- Any spill or accidental release can be quickly identified, because of ammonia’s strong odor.
According to the International Institute of Ammonia Refrigeration (IIAR), ammonia is 5 to 15% more thermodynamically efficient than competitive refrigerants. This allows an ammonia-based refrigeration system to achieve the same cooling effect while using less power. As a result, where ammonia refrigeration is incorporated, its overall system can provide a Low Life Cycle Cost Analysis (LLCA) , low carbon emission where the system gets greener and the energy savings add to the bottom line footprint. This could also be a door opener in obtaining LEED certifications from the USGBC’s local chapter and an eventual recipient to OSHA’s PSM &EPA’s RMP certifications.
Ammonia breaks down in the environment very quickly (lasting less than a week in the air). Unlike synthetic refrigerants like CFCs, it doesn’t damage the ozone layer. Most of ammonia’s potential for harm relies on there being too much of it in one place, not on its being leaked and scattered into the environment. Also, ammonia is mostlyused as a fertilizer and sprayed on fieldsfor industrial farming.
Also, in the event of any leak most people will notice the pungent smell of ammonia when it’s only about 20 parts per million (ppm) in the air. While some refrigerants have no noticeable smell, allowing small leaks to go unnoticed, that’s not the case with ammonia. Even a tiny amount in the air will be obvious. Importantly, the detectable concentration is much lower than the concentration that will cause immediate harm.
Limitations of Ammonia Facilities
The ammonia’s properties are best suited to large refrigeration systems, there is likely to be a large amount of ammonia in any system that uses it. Any water in the system would freeze and obstruct piping, so ammonia refrigeration systems uses anhydrous (dry) ammonia (without water or other impurities). The physics of vapor-compression refrigeration require the system to use enough pressure to compress the gas into liquid. Together, this means the refrigeration system uses required amount of pure ammonia under high pressure.
As a result, any ammonia-based refrigeration system may present a risk of accidental exposure to high concentrations of ammonia. That kind of accident could cause serious harm to worker health and safety.
OSHA considers anhydrous ammonia to be “immediately hazardous to life and health” at a concentration of 300 parts per million (ppm), or 0.03%. Ammonia is corrosive to the skin, eyes, and lungs, and even a brief exposure can result in severe chemical burns. Extreme cases can even prove fatal. Refer to ammonia safety and health information from OSHA.
Preventing an Ammonia Leak
OSHA recommends, among other steps, conducting a process hazard analysis (PHA) when ammonia refrigeration is present in a workplace. A PHA is a key component of broader Process Safety Management (PSM) efforts. It consists of a careful review of potential problems—such as an ammonia leak—and steps to be taken to prevent such an outcome. Conducting this analysis may raise awareness among employees, promote a mindful attitude about safety, and engender a proactive approach to hazard and risk assessment.Requirements for PHAs can be found in compliance with 29 CFR §1910.119, OSHA’s standard for Process Safety Management (PSM) of Hazardous Chemicals.
Safety on Ammonia Refrigeration System
The risks involved with ammonia refrigeration are substantially reduced by EPA’sRisk Management Program (RMP) and preventive maintenance. Part of that process is clear labeling of incorporated pipes and equipment . As the accepted industry experts in this field, the IIAR maintains a code of recommendations for refrigeration equipment labeling.
Last updated in April 2014, IIAR Bulletin No. 114( a copy can be ordered from iiar.org) specifies sizes, colors, and arrangements for ammonia pipe and component labels. This coherent system simplifies maintenance and promotes safety, and is compatible with ANSI/ASME A13.1, the most widely-used industrial standard for general facility Pipe Marking.
There are five elements in a typical ammonia Pipe Marker:
- Piping abbreviation, such as “LTRS” for Low Temperature Recirculated Liquid, to identify the part of the system that the pipe represents
- Physical state of the pipe’s contents, indicated with the word ‘Ammonia’, shown with letters on a colored band: “LIQ” on yellow, for liquid; “VAP” on sky blue, for vapor; or both if the pipe could contain both phases
- Pressure level, shown with letters on a colored band: “LOW” on green, for contents at 70 psig or less; or “HIGH” on red, for contents above 70 psig
- Flow direction, indicated with an arrow pointing along the pipe in the correct direction
The piping abbreviation, pipe contents, and flow direction would be shown in black print on an orange background. Under the popular ANSI/ASME A13.1 pipe marking standard, that is the preferred presentation for pipes carrying toxic contents, such as ammonia. As a result, a pipe marker that matches IIAR Bulletin No. 114 also matches the broader standard.
Afree ammonia pipe marking reference chart describing the IIAR’s pipe marker system can be furnished by Graphic Products. Using this chart can help one’s facility maximize its safety and efficiency, simultaneously taking advantage on the proven power of ammonia refrigeration.