New Mexico Pipe Fitter Journeyman (JPF) Practice Exam

Which pipe joining method is not typically used for thermoplastic pipes?

1. Flanging

2. Welding

3. Cementing

4. Grooved joints

The correct answer is: Welding

Welding is not typically used for joining thermoplastic pipes because it involves heating the materials to their melting points to fuse them together, a process that is suitable for thermosetting plastics or metals but not for thermoplastics. Instead, thermoplastic pipes are designed to be joined using methods such as cementing, flanging, or grooved joints, which do not require the application of high heat that could damage the material. Cementing, in particular, involves using a solvent that softens the plastic and allows for a chemical bond as it cures, making it a widely accepted method for thermoplastic pipes. While flanging and grooved joints can also be appropriate for certain applications involving thermoplastic pipes, they typically involve mechanical connections rather than heat. Therefore, when considering the best practices for thermoplastic pipe joining, welding stands out as an unsuitable method.