Solvent welding is a method of joining plastic pipe, usually used on PVC or ABS to achieve a high strength joint. In the process, the plastic in the joined surfaces is chemically melted, and joins together to a solid piece when the solvent evaporates. A properly made solvent weld will have a pressure rating equal to that of the individual parts. The joints will take some time to achieve full strength, cannons should be left to dry at least 24 hours before use.
Since a spudgun is operated at elevated pressures it is absolutely critical that all joints are properly glued. A proper glue joint not only prevents leaks but also insures the gun can be fired safely. It is highly recommended that you thoroughly read and understand the directions provided with the glue. See the External Links section for two excellent pages describing, in detail, the proper solvent welding technique.
For solvent welding of PVC pipe there are three products, two of which are absolutely required for a proper weld.
- PVC Cleaner is designed to remove oil, dirt, etc. from the PVC prior to gluing. It's use is usually considered to be optional. It is important though that the pieces being joined are clean and dry.
- PVC Primer (or primer / cleaner) cleans the pipe and softens the surface so the glue will take better. The use of primer is absolutely required for any joint that will hold pressure or carry a load.
- PVC Glue is a mixture of solvents and dissolved PVC and creates the actual bond between the two parts. Obviously, the glue is required.
For more information about these three see the PVC Reagent comparison page.
For solvent welding of ABS usually only ABS glue is used and the cleaning/priming step is omitted.
PVC glue (and primer) should not be used on ABS and vice versa.
Health and Safety
Solvent vapors are flammable and hazardous to your health, work should be done in a well ventilated area and away form ignition sources. The chamber of combustion and hybrid cannons should be vented before testing the ignition since the glue vapors can be ignited. Accidents have happened when solvent vapors have ignited in newly constructed guns.
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