Basic Joining Techniques
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There are several recommended methods of joining thermoplastic pipe and fittings, each with its own advantages and limitations:
The most widely used method in Schedule 40 PVC, Schedule 80 PVC and CPVC piping systems as described in ASTM D-2855. The O.D. of the pipe and the I.D. of the fitting are primed, coated with special cement and joined together, (described in detail below.) Knowledge of the principles of solvent cementing is essential to a good job. These are discussed in the Solvent Welding Instructions Section.
NOTE: The single most significant cause of improperly or failed solvent cement joints is lack of solvent penetration or inadequate primer application.
Schedule 80 PVC, CPVC, PVDF, and PP can be threaded with special pipe dyes for mating with Schedule 80 fittings provided with threaded connections. Since this method makes the piping system easy to disassemble, repair, and test, it is often employed on temporary or take-down piping systems, as well as systems joining dissimilar materials. Threaded pipe must be derated by 50% from solvent-cemented systems.
NOTE: Threaded joints are not recommended for PP pressure applications.
This technique is used to assemble PVDF and polypropylene pipe and fittings for high-temperature, corrosive-service applications. (See each manufacturer’s data for recommended joining techniques.)
This technique is used to assemble PVDF and polypropylene pipe and fittings for high-temperature, corrosive-service applications.
NOTE: See each manufacturer’s data for recommended joining techniques.
SMOOTH INNER BORE (S.I.B.)
S.I.B. offers state-of-the-art technology for sanitary piping systems construction. The “smooth” interior surface of the weld eliminates all beads, crevices and intrusions into the fluid system. Materials cannot become entrapped, and the possibility of bacterial growth and contamination is virtually eliminated. S.I.B. reduces pressure loss due to friction and improves system hydraulics. Available in Kynar® (PVDF) and polypropylene.