What is the most commonly used fasteners in boiler construction?

• A. Welded
• B. Bolted
• C. Riveted
• D. Threaded

Answer: (D)

Joints in boiler construction must be able to hold high pressure and withstand heat without leaking. Welding achieves that by fusing the metal pieces together to form a single, continuous shell or connection. This creates a strong, leak-tight boundary that can handle thermal expansion and cycling, which is essential for boiler operation. Because of these benefits, welding is the standard method for joining the pressure-containing parts of a boiler.

Threaded fasteners do appear for removable components, such as fittings, flanges, valves, or instrumentation, where disassembly is needed. They are not used for the main pressure shell joints because threads can become leak paths under high temperature and pressure and are less durable in the boiler environment. Riveting was common in older boilers, but modern practice favors welding for reliability and efficiency.

So the most commonly used method to join boiler components is welding.