Field and refinery term for assembling a bolted flange or vessel closure, covering face cleaning, gasket placement, lubrication and tightening in a star or crisscross pattern through several rising passes. A good bolt-up brings the flange faces together evenly so the gasket is compressed uniformly; uneven or single-pass tightening is a classic cause of leaks at hydrotest.
Bolt-up on the exchanger flange is three passes, thirty, sixty, a hundred percent, then circular passes till nothing moves.
Also heard as
- flange bolt-up
- bolting up
Related terms
B7
The chromium-molybdenum alloy stud grade that is the default for pipe flange and pressure vessel bolting.
Snug tight
The first stage of bolting, where the joint plies are pulled into firm contact before final tightening.
Stud
A headless rod threaded at both ends or along its full length, used with nuts or screwed into a tapped hole.
Preload
The tension created in a bolt by tightening it, which clamps the joint and keeps it from slipping or opening.