Use of spigotted PVC pressure fittings (VX-TN-5B)
Certain fittings in the Vinidex range of moulded pressure fittings have spigots for solvent cement jointing to sockets. It is important to recognise that these spigots are designed for use strictly with the sockets of other moulded fittings, not pipe sockets or fabricated fittings sockets.
The fittings referred to are:
- Cat. 1: Plain Take off Adaptors
- Cat. 2: Valve Take Off Adaptors
- Cat. 3: Faucet Take off Adaptors
- Cat. 5: Reducing Bushes
Most sockets for solvent cement joints are tapered to provide a certain interference fit. Interference may occur between spigot and socket anywhere (within certain limits) along the length of the socket, depending on the variations in dimensions of spigot and socket within the tolerance band allowable.
However, pipe sockets are longer than fittings sockets There are two reasons for this;
It is desirable for fittings to be as compact as possible for working in confined spaces.
The tolerance achievable in moulding is superior to that achievable in postforming sockets on the end of pipe.
It is therefore possible to design fittings with a shorter length of taper.
Spigoted adaptors are likewise designed with the spigot length to match the moulded fitting socket length. If an attempt is made to joint one of these spigots into a pipe socket, it is possible that interference will not be achieved between the shortest spigot and the longest socket. A faulty joint may therefore result.
Use of these fittings should therefore be restricted to the purpose for which they are strictly designed, ie. as the name implies, adapting fittings from one form to another.
In the rare circumstances where it is desired to adapt a pipe socket to a different form, either cut the socket off, or joint a short length of pipe into the socket and then use a female fitting.