Tack welding is a temporary weld that has sufficient tensile strength to hold the work pieces together
until further welding is performed. This operation does not require a welding rod or a flat strip.
Hand welding and high-speed welding both require a welding rod or a strip of thermoplastic
material. The welding rod or the strip is generally of the same material as the parts that are to be welded.
Welding, however, is not limited to fastening two identical pieces together. It can also be used where
another substance, such as a metal screen, may have to be fastened to a thermoplastic.
In general, welding is one of the last operations on a structure. This means that all previous operations
such as cutting, heating, bending, and beveling will have been completed. All parts have to fit dimensionwise.
Once welded, it will be rather difficult, if not impossible, to repair mis-fitted parts.
Scrap pieces of all types, shapes, and thicknesses are useful for the training of beginners in various
welding methods. This includes polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC),
plasticized tank linings, and other thermoplastics.
The basic took for all three types of hand welding are: the welding gun (often called welding torch or
simply welder), metal tips, pliers, and cutting knife. Air pressure, a combustible gas and/or electricity are
used to provide the hot air stream; i.e., water-pumped nitrogen or another inert gas is used instead of air
for polyethylene and, in some cases, for polypropylene.
Hot Gas Welder Components:
Each welder consists of the following basic parts: the heating element, air hose, barrel, air-cooled handle,
and cable with plug. Accessories include an air-pressure regulator and various metal tips and high-speed
tools. The same basic welder will perform all types of hand welding simply by inserting the proper metal
tips.