Manufacturers of hermetic compressors are turning their attention to alternative refrigerants that could represent a long-term solution to ongoing to government regulation. Although it’s commonly acknowledged that there is no one-size-fits-all answer, natural refrigerants, such as carbon dioxide (R-744), ammonia (R-717), and the hydrocarbon (HC) refrigerants propane (R-290) and isobutane (R-600), have been garnering attention.
According to John Prall, technical support, North American region, Embraco, propane appears to hold the greatest potential for widespread use in self-contained refrigeration systems. He noted ammonia is highly toxic; carbon dioxide operates at very high pressures and does not condense well in hot environments; and, although propane and isobutane have similar properties, propane is better suited for hermetic compressors with larger displacements. Both propane and isobutene, however, are flammable, and that has been a major cause for concern among refrigeration contractors and their technicians. But, through proper training, good awareness, and some basic safety procedures, the risk of working with flammable refrigerants is very manageable, said Prall.
SAFELY USING PROPANE
In a presentation at a recent meeting of the Refrigeration Service Engineers Society (RSES), Prall offered the following safety tips for working with equipment that uses propane as a refrigerant.
Look for the label — Systems that use HC refrigerants are required to have a yellow warning sticker that identifies the refrigerant and states, “Caution, risk of fire.”
“The yellow sticker says there is an element of risk, and, even though the risk is low, you must be cognizant of it,” Prall said. “You must be aware of the risks and treat the equipment with respect and caution, and that’s true every time — even after you’ve become comfortable working with flammable refrigerants.”
• Conduct a risk assessment — Determine whether it’s appropriate to use a flammable gas refrigerant in a particular workplace. The work area must be free from sources of ignition. Fire-extinguishing equipment should be present and easily accessible.
• Monitor for leaks — Monitor the work area using an HC detector located at a low level, because HCs are heavier than air. The detector should provide an audible and visual alarm well before there is enough HC in the air to form a flammable mixture (approximately 2 percent of HC by volume).
• Sparks are the enemy — When replacing or servicing electrical components in a system that uses an HC refrigerant, make sure all of the components comply with IEC/EN60079-15. Starting devices and overload protectors need to be sealed, and the fan motor needs to be spark-free (brushless).
“This is really critical,” Prall said. “In any kind of switch or relay you have two electric contacts coming together, and there’s always the risk of sparking or arcing. They must be sealed so that none of the HCs can possibly get into the area where there’s the potential for a spark.”
This is particularly important in devices that have a large number of electronic switches, controls, and motors, such as vending machines and ice machines.
• Use the right tools and equipment — Use only tools and apparatus certified for use in hazardous areas, and wear an anti-static electricity tag.
Although HCs can be vented into the atmosphere, in cases where a recovery machine is going to be used, it should be specifically designed for HCs. Standard recovery machines for HFC refrigerants can’t be used because of inbuilt sources of ignition, such as relays and high- and low-pressure switches. In addition, recovery cylinders must be specific for HCs and must carry the proper markings.
A MANAGEABLE RISK
Although HC refrigerants are flammable, to a well-trained technician who uses due diligence and understands the workplace, they’re far less dangerous than servicing other items, such as high-voltage equipment, Prall said. “There’s risk, and then there’s manageable risk. Keep in mind that refrigeration circuits using R-290 are limited to 150 grams of charge. Meanwhile, we think nothing of having a canister containing 15 pounds of propane attached to the grill on our deck. The level of risk with these refrigeration systems, when approached properly by a trained technician, is very low. We in the industry have to communicate the risks and make sure they’re understood and kept in perspective.”
For more information, visit http://www.rses.org/hydrocarbons.aspx
Publication date: 12/7/2015