Arkansas HVACR NewsMagazine May 2022

HVACR NewsMagazine May 2022

Tech News

Doing a visual inspection to find obvious leak indicators

CRTs. It’s best to avoid using manifolds whenever possible, as manifolds create more potential leak points.

First of all, you’ll want to do a thorough visual inspection. If you’ve just installed new copper, you should have already checked each joint with a mirror. However, if you’re working on a system for the first time, check for leak indicators like oil spots. You may also want to bubble-test the Schrader cores (and core removal tools, which we recommend using) to see if they’re leaky. It’s best to put a cap on the Schrader port WITHOUT a seal so that you can check for leaks without spraying bubble solution directly into the Schrader ports. If the cores are leaky, you’ll want to replace those and eliminate them as a potential leak source. Ensure that your caps and hoses have the appropriate seals, as those could be leak points. After you’ve inspected the joints, Schrader ports, and other leak- prone areas, it’s time to hook your hoses up to the Schrader ports by using core remover tools. As said before, make sure these hoses have the proper seals; you can even bubble-test your hoses as well to make sure they aren’t leaky. Once you’ve hooked up your hoses, purge the system by sending nitrogen through the lines. Again, purging is different from flowing, as it typically occurs at a rate anywhere between 20 and 100 SCFH at high pressure, whereas we usually only flow nitrogen at a rate of 2-5 SCFH at low pressure. Then, you can apply your pressure probes to the system. It’s best to use core remover tools and tighten the probes down right at the Preparing the system for a standing pressure test

Pressurizing the system with nitrogen

Typical pressurization rates can be anywhere between 250 and 600 PSI. Since that’s quite a range, you’ll want to look up the manufacturer’s literature and see what the manufacturer recommends exactly. When in doubt, err on the side of caution to avoid over pressurization and causing damage. When you reach the desired pressurization rate, you can valve off nitrogen from the system. (Again, that’s why core removal tools make standing pressure tests so much easier.) After the nitrogen has been valved off from the system, let it stand for at least 30 minutes (the longer, the better; some larger commercial systems should really stand for at least 24 hours). While the system stands, monitor the pressure at the probes. At this point, you may add some leak reactant to the valves, flare fittings, bends, and other common leak areas to see if bubbles form. The pressure test is passed when the nitrogen pressure holds; there should also be no patches of bubbles on the leak reactant. Once you have a pass/fail verdict, you may release the nitrogen and either continue your work or rectify the leak source. If the equipment has failed the standing pressure test, then you need to pinpoint the leak to see what you exactly need to fix.

You may use a couple of different strategies to detect the leak.

Refrigerant leak detection: the bubble test You may do a “bubble test” with a leak reactant to confirm the location and extent of a leak. Chemical leak reactants create bubbles on the tubing’s surface, as the nitrogen that is attempting to escape the