Successful gasket installation depends upon following a good procedure
Gasket installation can be a tricky business! To be successful, gasket installation should always follow a well thought-out procedure. Following a good procedure will ensure a leak-free seal in every gasket installation you undertake.
The function of a gasket is to seal the two different surfaces of joint held together by fasteners, the most common being screw threaded devices such as bolts. The bolt acts like a spring - it is an elastic member that has been stretched to develop a load. The more spring provided by the bolt, the better the retention of stress on the gasket to maintain a leak proof joint. It is not a regularly published statistic, but almost 70 per cent of all gasket failure’s are caused due to a lack of bolt load stress forced onto the gasket surface.
A common misconception is that the gasket fails because it has been improperly selected for the application in question. However, that is true in likely in less than 10 per cent of all cases. Rather, it is the gasket installation that is the key to any success in obtaining a leak-free joint. Below are some guidelines for achieving a successful gasket installation:
Remove the old gasket and clean the flange surfaces of all debris. For best results, use a flange scraper, an aerosol gasket remover and a wire brush to remove debris. Inspect all flange surfaces for damage and repair as necessary.
Ensure that the right gasket is selected for the application. Use the thinnest possible gasket because they require less torque. Contact CRGI if you need guidance on selecting the right gasket for your particular application.
Whenever possible, use ring gaskets. Full face gaskets have more surface area, requiring additional compressive load on the gasket.
Most, if not all, gasket manufactures now use anti-stick coatings on the surfaces of their finished sheet goods from which the gaskets are cut. Never use metal based anti-seize products, since particles may accumulate in the surface imperfections, creating a flange surface which is too smooth to be effective.
Center the gasket on the flange. Standard ANSI ring gaskets, when cut properly, should center themselves when the fastening bolts are in place.
Use well-lubricated fasteners with hardened flat washers to ensure correct initial loading. Use a torque wrench to tighten fasteners. By using anti-seize for lubrication use, you can increase your torqueing capability by as much as 50 per cent.
Tighten bolts to compress the gasket uniformly. This means going from side to side around the joint in a star crossing pattern. See the diagram below for common bolting patterns.
All bolts should be tightened in one-third increments, according to proper bolting patterns. Use B-7 or B-8 bolts whenever possible.
Re-torque all fasteners 12 to 24 hours after start-up, whenever possible. All applicable safety standards must be followed.
By following this procedure for gasket installation, you now have a leak-proof seal that will be worry-free for a long time, depending on the operating conditions of your particular gasket application.
Bill Searle welcomes comments or questions on any aspect of this blog post. Contact Bill directly at crg@canadarubbergroup.com.