Why is proper torque sequence important when tightening multi-bolt flange joints?

Why is proper torque sequence important when tightening multi-bolt flange joints?

• A. Allows bolts to loosen under vibration.
• B. Ensures even load distribution and proper gasket seal to prevent leaks.
• C. Reduces the need for lubrication.
• D. Increases assembly time.

Answer: (B)

The idea behind proper torque sequence is to produce an even clamping force across the flange so the gasket is compressed evenly and the joint seals reliably. If bolts are tightened in a random order, some bolts reach final tension before others, which pulls the flange unevenly. That uneven load can leave parts of the gasket under- or over-compressed, create gaps, and even distort the flange. The result is an unreliable seal and a higher risk of leaks, especially with temperature changes and vibration found in aviation. Using a cross or star pattern helps gradually bring the flange into proper alignment and applies tension around the entire circle so every area of the gasket seats evenly. Usually you tighten to a light initial torque in that pattern to seat the components, then move to the final torque in the same pattern, sometimes rechecking after seating or thermal cycling. This approach minimizes bolt bending and reduces the chance that one bolt bears excessive load, which would raise fatigue risk. As for the other options, the goal isn’t to allow loosening under vibration, nor is it about reducing lubrication needs or simply increasing assembly time. The real purpose is to ensure a uniform seal by even load distribution.

The idea behind proper torque sequence is to produce an even clamping force across the flange so the gasket is compressed evenly and the joint seals reliably. If bolts are tightened in a random order, some bolts reach final tension before others, which pulls the flange unevenly. That uneven load can leave parts of the gasket under- or over-compressed, create gaps, and even distort the flange. The result is an unreliable seal and a higher risk of leaks, especially with temperature changes and vibration found in aviation.

Using a cross or star pattern helps gradually bring the flange into proper alignment and applies tension around the entire circle so every area of the gasket seats evenly. Usually you tighten to a light initial torque in that pattern to seat the components, then move to the final torque in the same pattern, sometimes rechecking after seating or thermal cycling. This approach minimizes bolt bending and reduces the chance that one bolt bears excessive load, which would raise fatigue risk.

As for the other options, the goal isn’t to allow loosening under vibration, nor is it about reducing lubrication needs or simply increasing assembly time. The real purpose is to ensure a uniform seal by even load distribution.