What is a torque sequence, and why is it critical when tightening multiple bolts on a flange or assembly?

• A. The prescribed order to tighten bolts to equalize stress; prevents warping and leaks and ensures even clamping.
• B. Tighten bolts in any random order.
• C. Start with the bolts at the outer edge first.
• D. Tighten bolts only after painting the flange.

Answer: (A)

A torque sequence is the prescribed order to tighten bolts so the clamping pressure is distributed evenly around the joint. This pattern draws the flange together uniformly, which prevents warping or bending and ensures the gasket seats evenly, reducing the chance of leaks. Tightening in the correct sequence—often a star or crisscross pattern and in multiple passes (light to final torque)—lets each bolt share load similarly and avoids concentrating force on a few bolts first. If you tighten in a random order, some areas can become distorted, leading to leaks or bolt failure. The idea of starting at the outer edge or painting the flange doesn’t address how the joint is loaded, so those approaches don’t ensure an even seal.