Refrigerants are pervasive in air-conditioning and refrigeration equipment, certain fire suppression systems and other industrial applications. Refrigerant leaks aren’t only costly, but pose a safety and environmental hazard. Unfortunately, many refrigerants can’t be seen, smelled or tasted, which makes leak detection difficult.Refrigerant leak detection: An appropriate selection from the many leak detection technologies available is a function of refrigerant type, system size, configuration, location and physical environment. Tight spaces or barriers to access, breezes, ambient light and excessive noise influence the decision.Electronic sniffers, bubble tests, halide torches, fluorescent dyes and water immersion are among the tools commonly used to detect refrigerant leaks. More recent additions include infrared, ultrasonic and advanced heated diode detectors.Infrared leak detectors: Infrared (IR) leak detectors selectively monitor refrigerant gases and aren’t subject to false readings from other gases or contaminants. These detectors are equally sensitive to a wide range of refrigerants including newer refrigerants and blends. Humidity, smoke, air flow or temperature changes won’t hinder detection speed and accuracy. The devices have a longer life, providing low overall cost of ownership.One example is Bacharach’s model H25-IR. This industrial refrigerant leak detector uses infrared absorption technology to locate and quantify low levels of nearly 30 refrigerants and halogens in less than one second.Ultrasonic leak detectors: Ultrasonic detectors are sensitive to hissing sounds associated with gas leaks, although they aren’t gas specific. When focused on a specific sound, ultrasonic devices can filter out background noise. Direct access to the leak isn’t always necessary. Leaks from high-pressure fittings cause greater turbulence and are easier to locate – even if the source is outside the line of sight. High-quality headphones are recommended to make the most of this technology.The AccuTrak ultrasonic leak detector by Superior Signal is most sensitive to sounds around 40 kHz, which is twice the highest frequency the best human hearing can detect. The unit can filter out wind noise, voices, traffic and most normal operational sounds.Advanced heated diode detectors: Electronic heated diode sensors used to be prone to false alarms or were sensitive only to specific refrigerants. Large leak exposure slowed sensor recovery and shortened life. The detectors weren’t fully adaptable to newer refrigerants. Newer models have overcome many of these limitations.TIF ZX-1 from Advanced Test Products, for example, features a heated pentode sensor that can detect halogenated refrigerant leaks as small as 0.1 oz/yr. The Bacharach H10Xpro uses a dispersed electron heated triode sensing element to detect every refrigerant.Current safety standards: Standard 15, Safety Standard for Refrigeration Systems, from the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) specifies safe design, construction, installation and operation of refrigerating systems. Doug Reindl, chair of the Standard 15 committee, encourages owners of refrigerant systems to become familiar with the ANSI/ASHRAE 15-2004 safety standard.“Some companies are making it a policy to keep their systems compliant with current safety codes, even if local authorities permit ‘grandfathering’ in the absence of equipment additions or changes that aren’t replacements in-kind,” says Reindl.ASHRAE Standard 15 classifies refrigerating systems according to the degree of probability that leaks from a failed connection, seal or component could enter an occupied area. Based on this designation, high-risk systems can be assigned accelerated maintenance and inspection schedules.ANSI/ASHRAE Standard 15-2004 clarifies the application of safety relief valves on larger pressure vessels. Safety relief valves minimize refrigerant loss to the atmosphere in case of a burst rupture disk. “Make sure your design and build contractors provide adequate documentation of how your safety relief systems are sized and engineered so that you have evidence of proper implementation,” Reindl recommends.Among other requirements, the standard specifies that refrigerating machinery rooms must have a leak detector that actuates an alarm and mechanical ventilation. One exception is ammonia-based systems, although Reindl notes that many industrial plants are installing leak detection systems for ammonia systems as a best practice. Ammonia detection systems help protect personnel and infrastructure by sensing refrigerant leaks and triggering alarms or mitigation systems.E-mail Contributing Editor Sheila Kennedy, managing director of Additive Communications, at [email protected].
Reference Web sites: www.bacharach-inc.com www.superiorsignal.com www.advancedtestproducts.com www.ashrae.org www.ansi.org www.irc.wisc.edu |