Pipework practice: flanges may be attached to pipes by which of the following methods?

Introduction / Context:
Flanges provide detachable joints in piping systems. The method of attaching a flange to pipe depends on pressure–temperature rating, material, service, and installation constraints. Common attachment types include threaded, welded, and—where appropriate—brazed connections, though the latter is limited to certain alloys and lower-temperature services.

Given Data / Assumptions:

• Industrial piping following typical codes and standards.
• Materials compatible with the chosen joining method.
• Service conditions within the allowable limits for each method.

Concept / Approach:
Threaded (screwed) flanges are used on small-bore, low-to-moderate pressure lines for ease of assembly. Welded flanges (weld-neck, slip-on, socket-weld) dominate in higher pressures and critical services thanks to structural integrity and leak tightness. Brazed flanges, while less common in heavy industry, are used in HVAC, refrigeration, and certain non-ferrous or stainless systems where brazing is standard practice.

Step-by-Step Solution:

Verification / Alternative check:
Piping catalogs and standards show threaded and welded flanges as mainstream; brazed connections appear in specialized systems and OEM equipment.

Why Other Options Are Wrong:

• Selecting only one method ignores common practice variety; the comprehensive option is correct.

Common Pitfalls:
Assuming brazing is universally acceptable; it must meet code and service limitations. Critical and high-temperature services normally require welded flanges.

Final Answer:
All (a), (b) and (c)