What can flange rotation during pressurization result in?

• A. Loss of gasket compression
• B. Improved gasket seating
• C. Reduced bolt load requirements
• D. Faster pressurization

Answer: (A)

When a bolted flange joint is pressurized, the gasket relies on a uniform clamp from the bolt preload to keep the gasket compressed and the faces in firm contact. If the flange rotates during pressurization, a moment is created about the bolt circle that alters how the bolt loads transfer around the circumference. This rotation tilts the flange faces relative to each other and changes the alignment of the gasket contact, so the clamping pressure becomes nonuniform and can drop in places. The result is a loss or uneven distribution of gasket compression, creating potential leakage paths. In short, rotation weakens the seal by reducing the gasket’s compression rather than improving seating, reducing bolt load requirements, or speeding up pressurization.