The “Weakest Link” Theory: Why 80% of Flange Leaks are Caused by Poor Bolting Practices

A Flange is a Spring Engineers often forget that a flange joint is a live mechanical system. When you tighten the bolts, you are essentially “loading a spring.” If the bolting is uneven or the material is inferior, the joint will fail during the first thermal cycle.

1. The Danger of “Black Oxide” vs. Zinc Plating In corrosive offshore environments, standard black oxide B7 bolts will rust within weeks. DTC Flowtech recommends PTFE (Xylan) coated or Hot-Dip Galvanized fasteners. The coating doesn’t just prevent rust; it provides a consistent friction coefficient, which is critical for achieving the correct Bolt Torque.

2. Gasket “Crush” and Recovery A common mistake is over-tightening the gasket until it’s permanently deformed. A high-quality DTC Spiral Wound Gasket is designed to have “recovery”—it acts like a spring to maintain the seal even as the flange expands and contracts.

DTC Expert Tip: Always specify Graphite filler for high-temperature service (>260°C). PTFE filler is excellent for chemical resistance but will “creep” or flow under high heat, leading to potential leaks.