Gasket installation & bolt-up best practice
Most flange leaks are assembly faults, not material faults. This guide covers the preparation, torque pattern and re-check routine that make a joint seal first time.
Prepare the flange faces
Clean both faces back to bare metal, remove all old gasket material, and inspect for radial scoring, pitting and flatness. A scratch across the seating face is a guaranteed leak path. Never reuse a gasket, and never stack two gaskets to make up a gap — correct the flange or the spacer instead.
Lubricate and align
Use new, correctly specified bolts and a known thread lubricant so your torque produces predictable bolt load — under-lubricated threads can lose half the intended clamping force to friction. Centre the gasket, align the flanges by hand, and bring the nuts to finger-tight before applying any torque so the joint pulls up square.
Torque in the right pattern
Tighten in a cross (star) pattern in at least three passes — roughly 30%, 60% and 100% of target torque — then finish with one or two rotational passes around the bolt circle. This seats the gasket evenly and avoids cocking the flange. Use a calibrated torque wrench and the gasket manufacturer's seating-stress-based torque, not a rule of thumb.
Re-torque after settling
Soft and spiral-wound gaskets relax slightly after first compression and after the first thermal cycle. Where the construction and procedure allow, re-torque the joint to target once it has settled (and, for hot service, after it has reached temperature and cooled). Record the final torque so the joint history is auditable.
Take it from reference to recommendation.
Send your service conditions — media, temperature, pressure and motion — and our engineers will specify the exact seal, material and construction for the duty.