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INFICON believes a changeover to more environmentally friendly HFO refrigerants for heavy-duty trucks and off-highway vehicles is inevitable and will require the adoption of more stringent AC-system quality-control checks. (INFICON)

Leak testing of commercial-vehicle AC systems critical as move to HFO refrigerants looms

Passenger car and light-truck makers in the U.S. already have switched to more environmentally friendly hydrofluoroolefin (HFO) refrigerants from hydrofluorcarbons (HFCs) to meet EPA requirements prompted by global-warming concerns. Though similar standards are not yet in place for commercial vehicles, heavy-duty truck and off-highway equipment manufacturers need to prepare for an “inevitable” switch to the more expensive and flammable air-conditioning refrigerants, according to Thomas Parker, North American sales manager for INFICON.

“As the use of HFCs in cars and in other markets outside the U.S. is phased out, market supply-and-demand undoubtedly will push OEMs to eventually make a switch to HFOs,” even without government mandates, Parker told Truck & Off-Highway Engineering. Though, regulations for HD trucks and off-highway equipment could come within the next two to three years, Parker speculated, with on-highway commercial vehicles likely being affected first.

Most heavy-duty trucks are equipped with air-conditioning, and Parker estimates that more than 80% of all farm combines and tractors, as well as construction, mining and other off-highway vehicles come equipped with AC systems. INFICON, a global supplier of leak-detection equipment, says the changeover to HFOs will require the adoption of more stringent AC-system quality-control checks as well.

“Fewer than 20% of the heavy-duty trucks, farm tractors and other off-highway vehicles receive thorough leak-detection tests on their AC systems before they leave the factory,” said Parker. Without government requirements and with less-flammable, less-expensive HFCs still in use, there’s less pressure on OEMs to adopt leak-detection testing for cost, quality-control and safety reasons.

“That will have to change in the near future,” he added. “Newer, more environmentally friendly refrigerants are not only more flammable, but they also can form dangerous acids if placed in contact with water vapor.”

Although nearly 10 times more expensive, an HFO’s life cycle in the atmosphere is only about 11 days compared to up to 200 years for HFCs, according to INFICON. The newer automotive HFOs also have a rating of 4 on the Global Warming Potential (GWP) scale, while HFCs are rated at more than 1,300.

HFO refrigerants like R-1234yf used for automotive cannot be directly applied to heavy-duty trucks and off-highway vehicles. For example, various changes need to be made to the engine cooling system.

“As a refrigerant, HFO is 10-12% less effective than HFC,” Parker explained. “To compensate for the loss in efficiency, an additional heat exchanger might be required that can be built in the suction and discharge hoses called an IHX (internal heat exchanger) hose. AC hoses might need to be changed or improved, and different viscosity oils and new lubricants may be called for.”

Automotive standards, while helpful, often don’t fully account for customer needs in the heavy-duty and off-highway marketplace. For example, customer needs in the commercial-vehicle market go well-beyond comfort and convenience, Parker noted. “There are a variety of government and union-mandated requirements that affect HD trucks, mining equipment and other commercial vehicles that need to be taken into consideration,” he said. “Unlike most passenger cars, HD/commercial vehicles often are in constant service or have continuous duty requirements.”

Parker predicts that a change to HFO refrigerants could take from two to four years once government regulations are in place, although one heavy-duty manufacturer already is making the switch. He could not divulge the name of the manufacturer but did confirm that INFICON is working with the company to develop and implement a leak-detection program to meet those requirements and is helping to train employees on the use of leak-detection equipment.

The equipment and processes used for the automotive industry essentially can be applied directly to heavy-duty truck and off-highway vehicle testing, though HD/off-highway systems are larger in size. “Longer hoses, bigger compressors and heat exchangers make for larger internal volumes that require more refrigerant charge and more money in charge,” Parker said.

The INFICON executive points out that early leak detection is important at every stage of the manufacturing process, but especially on the final assembly line. He recommends robotic or operator-managed helium-based leak tests for every AC system component, including heat exchangers, AC hoses, connectors, compressors and O-ring connectors.

“In addition, manufacturers should perform a refrigerant-only ‘sniff’ test on the final-assembly line to ensure that engine-run tests haven’t created additional leaks,” he said. “This offers an opportunity to test for fuel and hydraulic leaks, as well.”

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