Depending on the unit you are working on, service valves vary and will be different. Figure 26-1 shows some different service valves. Service valves are devices that allow access to the sealed refrigeration system. The most economical way this is done is by crimping. This procedure is done at the factory. A small length of copper tubing is attached to the suction side and high side of the system. When the proper amount of refrigerant charge has been placed into the system, the tubing is crimped and soldered closed. When this is completed, there isn’t a way to get back into the system. In Fig. 26-2 a crimped access is shown.
The next type service valve is called a line-tap-valve. Figure 26-3 shows one of these. This valve is used on soft copper and doesn’t require soldering. It is installed with the use of screws. One of the disadvantages of this type of valve is its potential to leak. A small rubber “0” ring seals the valve to the refrigerant line and is the weak link in the chain. If used on a discharge line, the valve has a limited life due to the temperature variations being applied to the rubber “0” ring.
The most common service valve used on small equipment is the Schraeder valve. This valve is pictured in Fig. 26-4 and is very familiar to all for it is used on both the low and high sides of the refrigeration system. Located in the hoses of your service manifolds are indenters. These push the core of the Schraeder valve open when the ‘/4-inch fitting is tightened onto the valve. The actual piece that holds the pressure is the valve core. The valve cores are replaceable with a valve extractor. Caution should be used when this type of valve is used on a liquid line. Liquid refrigerant has a tendency to spew when these valves are opened and closed. Burns will result if refrigerant touches your skin. If a crimped type of seal is being repaired, the Schraeder valve can be used. This valve can be acquired with a small length of copper tubing soldered to it. These access valves are soldered into place instead of crimped in the line.
The packed, angle-type valve is found in more expensive types of refrigeration equipment and air-conditioning systems. As shown in Fig. 26-5 it is entirely different from any of the previous valves mentioned. This valve has an actual valve stem that moves back and forth to open and close a valve from its seat. The valve stem passes through a gland nut on the outside of the valve. The packing within this gland nut keeps the refrigerant from leaking out of the system. A small wrench with a ratchet called a refrigeration service wrench is used to open and close this valve. On most semi-hermetic compressors this type of valve is used as the service valve and king valve on the receiver. Some versions of this valve require an Allen wrench, instead of a service wrench, for adjustment.
This type of valve is the safest to use since you have constant control of the refrigerant.