Preparation is everything they say, and that’s certainly true for flanged pipe connections. As flanges are brought together and the bolts tightened, the flange gasket compresses and flows into surface irregularities. If those are too severe for the gasket material to fill, the joint will leak. Here’s some advice on flange preparation.
Step 1: Inspection
Examine both flange faces carefully for damage like cracks, dings, burrs and radial scoring. Scoring is the worst problem as this will almost certainly create a leak path. Also check for alignment and verify that the faces are flat and parallel. (It’s possible for flanges to warp if the bolts are tightened in the wrong sequence.) Some softer gaskets will tolerate flanges being slightly out of parallel, but this does depend on the material being used.
Also check bolts, nuts and washers for signs of damage or corrosion. If in doubt as to fitness for purpose, opt to replace.
Step 2: Clean the Mating Faces
It’s common for traces of the old gasket to remain on the flange surfaces. These can be removed with a wire brush or scraper. However, to avoid damaging the flange face, this must be made from a softer material. Brass is usually a good choice. Always brush in a circumferential direction and not radially.
Step 3: Preparation
Inspect the new gasket for damage and ensure that it’s the correct size for the joint. Don’t use any kind of sealant on the gasket or sealing faces unless specifically advised to do so by the gasket manufacturer.
Proper torque tightness is essential to deform the gasket and seal the joint. If there’s excessive friction bolts will seem to be at their torque limit when they’re not, resulting in leaks. This can be avoided by lubricating the threads and under the heads of the bolts. (Ensure the lubricant is compatible with expected service conditions.)
Do it once
Inspection and cleaning may seem time-consuming, but doing a job once is better than having to fix a leak. That’s why thorough preparation of flange surfaces is so important. Contact Hennig Gasket & Seals for custom manufacturing of flange gaskets to your exact specifications.
