Joining Method PEX
There are several types of fittings for joining PEX. The various types of fittings are governed by ASTM specification. The "print stream" on PEX tubing indicates the applicable ASTM fitting specification suitable for that tubing. Two of the connection methods for PEX are made using Press stainless steel sleeves or PEX crimp rings. The stainless steel PEX Press sleeve connection compresses around the tubing and insert fitting in two places, permanently securing them together. The sleeve is fully inserted over the end of the tubing and the press fitting is inserted until it engages the stainless steel press sleeve. The connection is made using a PEX Press hand tool or PEX Press power tool recommended by the manufacturer. The connection must meet or exceed the requirements of the ASTM F 877 or appropriate fitting standard when tested with the manufacturer’s PEX tubing.
The PEX Crimp ring connection compresses around the tubing and fitting in a full circle, permanently securing them together. The PEX crimp ring is slid over the end of the tubing, and then the fitting is inserted into the pipe. The fitting is full inserted once it engages the shoulder or tube stop of the fitting. The connection is made using a PEX crimp hand toll recommended by the manufacturer. The connection must meet or exceed the requirement of the ASTM F 877 or appropriate fitting standard with the manufactures tubing.
Two other popular ways of joining PEX involve pre-expansion of the diameter of PEX tubing. Certain types of PEX tubing have "shape memory" that allows the tubing to return to its original diameter after being expanded. The two types of pre-expansion fittings are governed by ASTM F 1960 and F 2080. Prior to expansion, the outer diameter of a F 1960 or F 2080 fitting is larger than the inner diameter of the tubing; hence, without expansion of the tube, the fitting cannot be inserted into the tube. For F 1960 fittings, the external ring is made of the same type of PEX used to make the tubing; however, the ring is over-sized to the extent that it will slip over the outer diameter of the tube. For F 2080 fittings, a short brass sleeve is first place over the outer diameter of the tube.
In an F 1960 connection, the ring is positioned so that its trailing edge nearly lines up with the cut-end of the tube. Using a special expansion tool, the diameter of the tube and ring are then simultaneously expanded. Immediately after expansion, the tool is withdrawn and the fitting is inserted into the expanded tube/ring. The shape memory of the tube and ring then cause the combination to shrink back onto the fitting and hold it permanently and firmly in place.
In a F 2080 connection, the brass sleeve is first inserted over the tube and positioned a short distance past the cut end of the tube (an adequate distance so that the ring does not overlap the nose of the expansion tool when it is inserted into the tubing). The tube is then expanded, the expansion tool withdrawn, and the fitting inserted into the tool. A special tool is then used to pull the brass ring over the section of the tube that encases the inserted portion of the fitting. Between the shape memory of the tube and the compression action of the brass sleeve, the fitting is held permanently and firmly in place/
For most of the types of PEX connections, engineered plastic fittings are increasingly popular replacing traditional brass versions. Plastic fittings typically offer both economic and performance advantages.