Chapter 4 Page 3
Access valves have been developed which can easily be installed on either steel or copper tubing. They can be installed almost anywhere on the system and without loss of refrigerant even if the system is under pressure. After installation, they become a permanent part of the system. Normally, one is placed on the high side of the system, usually on the 2nd discharge line, and one on the suction line on the low side of the system. There are sizes available to fit all the existing tube sizes The valve consists of a valve body, a self-sealing steel pin containing a tube-piercing point, a valve core, and a cap. To enter the sealed system, the valve body is silver-brazed to the tubing at the point chosen for entry. The steel pin is then inserted into the valve body and the cap is screwed down tightly. The cap will force the steel pin down and cause the hardened hollow point to penetrate the tubing. As the cap is tightened, its internal chamfer will roll the end of the valve body fitting over and lock the steel pin in place. When tightening the cap use two wrenches to avoid twisting or distorting the tubing.
The tube-piercing tip is tapered so that as it penetrates, a tight seal is formed between the tapered tip and the edge of the hole. The valve itself is kept closed by the spring-loaded valve core.
To open the valve, the core stem must be depressed, using a depressor type fitting or hose connector. The core only serves as a temporary valve seal for servicing purposes. For a permanent seal the valve cap must be screwed on tightly.
The valve core is spring-loaded for positive closing, but the pressure inside the system, being higher than atmospheric, will assist the spring in sealing even tighter. By the same token, if a system is under vacuum, the negative internal pressure will cause air to leak around the valve seat and into the system. It follows then that the best policy is to be sure the valve is always capped except when a gauge manifold hose is attached.
Below are examples of fittings that can be used to access the refrigerant system of a refrigerator. Note: Most of these valves except for the stem valve are temporary and should only be used to access the system for troubleshooting or recovering refrigerant from the system. These valves when removed would leave a hole in the system or if left on will eventually leak. Stem valves could remain on the system and should be used when evacuating and charging the refrigerant system.