EPA Section 608 Universal Certification ExamType II (High-Pressure Appliances)Medium
A technician is performing a leak test on a high-pressure system using a nitrogen-based trace gas and an electronic leak detector. Which of the following statements is TRUE regarding this method?
- AThe trace gas must contain a detectable amount of refrigerant.
- BNitrogen is a refrigerant and can be vented to speed up the process.
- CThis method is only suitable for low-pressure appliances.
- DElectronic leak detectors cannot detect nitrogen, only refrigerants.
Show answer & explanationAnswer & explanation
Correct answer: A. The trace gas must contain a detectable amount of refrigerant.
When using a trace gas for leak detection in conjunction with an electronic leak detector, the trace gas (typically nitrogen) must be mixed with a small amount of the system's operating refrigerant. The electronic leak detector is designed to detect refrigerants, not nitrogen. The refrigerant 'traces' the leak, allowing the detector to find it.
Why the other options are wrong
- B. Nitrogen is not a refrigerant and should not be vented; it's an inert gas used for pressure testing and purging.
- C. This method is suitable for both high-pressure and low-pressure appliances, and is often preferred for high-pressure systems.
- D. Electronic leak detectors are specifically designed to detect refrigerants, not inert gases like nitrogen.
Trace Gas Leak Detection
When using an inert gas like nitrogen for leak testing with an electronic leak detector, a small amount of the appliance's operating refrigerant must be added to the nitrogen to allow the detector to sense the leak.
- Nitrogen is the pressure medium.
- Refrigerant is the 'trace' element.
- Electronic detectors sense refrigerant.
Memory trick: Nitrogen pushes, but refrigerant 'sniffs' the leak out for the detector.