REFRIGERANTS
Ultra-sensitive sampling system and Diffusion gas detector leak response.
concentration levels due to a leak. Several of the limiting values of the safety standards, in addition to the OEL defined above, are the Short Term Exposure Limit (STEL) – a 15 minute TWA, Immediate Danger to Life and Health (IDLH), Oxygen Deprivation Limit (ODL)/Acute-Toxicity Exposure Limit (ATEL) and Practical Limit. Extended exposures to HFC or HFO refrigerants can cause adverse cardio and neurologic health effects or in higher concentrations lead to asphyxiation.
Ultra-sensitive sampling systems Ultra-sensitive Sampling Systems take advantage of a very sensitive, centralized gas sensor with MDLs as low as 1 PPM which likewise enables very low alarm set points of 5 to 10 PPM, an order of magnitude more sensitive than a safety based diffusion detector. In addition, having the sampling point as close to the leak source as possible improved the ability to detect low level leaks (see Figure 10 below).
The sampling system incorporates a pump to draw samples back to the sensor through detection points which are simple pneumatic tubing terminations without the need for electrical power and can be easily and safely be tie-wrapped near common leak sources such as coils or compressors. These sampling systems
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are ideal for commercial building applications with many possible leak sources that can quickly become diffused in the large spaces. The sampling points are easily located near those common leak sources where samples are drawn back to an ultrasensitive sensor enabling low ppm alarms and early leak detection in multiple locations.
Achieving emissions leak reduction and early warning in commercial refrigeration systems
In an EPA study of refrigerant emissions in retail refrigeration applications shows that compressors, condensers, evaporators and refrigerant feed lines and accounted for a total of 69% of the leak sources. In a mechanical room, these identified locations could account for up to 50% of the potential leak sources. To achieve effective early warning leak detection, the number of detection points should be associated with the number of common leak points of the refrigeration system. Ultrasensitive multi-point detection system can provide the most cost-effective number of detection points with the lowest possible MDL. Such multi-point sampling systems incorporate a centrally located ultrasensitive gas sensor and a sampling pump to draw samples from multiple points associated with the commercial
refrigeration systems. The detection points are simple, small pneumatic tubing terminations without the need for electrical power and can be easily and safely mounted on or near the leak source such as compressors, valves, and evaporator coils.
Gas detectors designed to help comply with ASHRAE 15 and 34, EN 378, and CSA B52 are to protect someone from entering a mechanical room with refrigerant concentrations that could be harmful to their health. These protection levels are outlined in the safety standards to be about 1000ppm, 8-hour TWA depending on the type of refrigerant being used in the equipment. The alarm set points, location and number of detection points outlined in the safety standards are typically insufficient for finding the more common, smaller leaks that add up to large annual refrigerant emissions, decreased efficiency and overall safety.
The table above summarizes the size of gas leaks, the likelihood that they occur and the recommended gas detection technology. It can be seen that Ultrasensitive, multi-point refrigerant gas detection systems have been successfully used to achieve BOTH occupant safety and early warning leak detection that enable emissions reduction, cost savings, improved maintenance, and efficiency of cooling systems used in commercial buildings.
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