Piping practice and joint methods: Are joints between pipes, fittings, and valves limited to screwed (threaded) or flanged connections only, and therefore not permitted to be welded, brazed, or soldered in typical piping systems?

Introduction / Context:
In piping design and technical drawings, understanding allowable joint types is fundamental for safety, cost, and code compliance. The statement claims that joints may be screwed or flanged but not welded or soldered. This question tests knowledge of the full range of joining methods used across materials (steel, copper, plastics) and service conditions (pressure, temperature, corrosion).

Given Data / Assumptions:

• Piping can be metallic (carbon steel, stainless steel, copper, brass) or nonmetallic (PVC, CPVC, PP, PE).
• Common connection methods include threaded (screwed), flanged, welded, brazed/soldered, and solvent-welded or fusion-welded for plastics.
• Codes and manufacturer specifications govern suitability (e.g., pressure class, temperature, media compatibility).

Concept / Approach:
Match joining method to material and duty. Steel process lines frequently use welding (butt weld, socket weld). Copper plumbing commonly uses soldering or brazing. Plastic piping often uses solvent welding (cementing) or heat fusion. Threaded and flanged joints are only two among several legitimate methods. Therefore, the assertion that welding or soldering are not used is incorrect.

Step-by-Step Solution:

Verification / Alternative check:
Review standard specs and isometric drawings: weld symbols, solder/braze callouts, and solvent-weld notes appear routinely. Bill of materials lists include weld neck flanges alongside welded spools, confirming variety in practice.

Why Other Options Are Wrong:
“Correct” contradicts widespread industry practice. The qualifiers about steam lines, PVC-only, or seismic restraints do not ban welding or soldering—those are application-specific nuances, not blanket prohibitions.

Common Pitfalls:
Assuming one method fits all materials; ignoring pressure/temperature limits of threads; misapplying solder where brazing is required by temperature; overlooking code-required weld procedures.

Final Answer:
Incorrect