Graphite packing is a highly resistant sealant used in systems with valves, faucets, and stuffing boxes, as well as other machines with watertight mechanical parts. It can be applied either to static valve stems or to moving joints. Graphite packing offers high chemical resistance, great lubricity, and excellent thermal conductivity. It is the choice of many industries because it is a reliable, cost-effective, and easy-to-install sealant.
There are two major factors to be considered with regard to gasket seating. The first is the gasket material itself. The ASME Unfired Pressure Vessel Code Section VIII, Division 1 defines minimum design seating stresses for variety of gasket materials. These design seating stresses range from zero psi for so-called self-sealing gasket types such as low durometer elastomers and O-rings to 26,000 psi to properly seat solid flat metal gaskets. Between these two extremes there are a multitude of materials available to the designer enabling him to make a selection based upon the specific operating conditions under investigation. Table 1 indicated the more popular types of gaskets covered by ASME Unfired Pressure Vessel Code.
A seal is affected by compressing the gasket material and causing it to flow into the imperfections on the gasket seating surfaces so that intimate contact is made between the gasket and the gasket seating surfaces preventing the escape of the confined fluid. Basically there are four different methods that may be used either singly or in combination to achieve this unbroken barrier.
In the present seal, metal spiral wound gasket with excellent elasticity, high temperature, high pressure,low temperature and other characteristics, has become a very wide range of applied seal. Especially suitable for uneven loading, relaxation and easy access together, cyclical changes in temperature and pressure of the occasion, is the main flange gasket. In the petrochemical pipelines, mechanicalseals,shipbuilding,metallurgy, aerospace and other industries widely.
Clean radius and straight cuts are achievable on gasket material with the proper tooling. Thinner types of gasket material require nothing more than sharp blades and hollow gasket cutters. Gasket material over 1/4-inch thick require specialized mechanical tools to create the precision cuts necessary to seal a piece of equipment and is best left to professionals. Properly securing the gasket material and ensuring the tools used are in good condition will allow you to cut thinner gasket material efficiently and precisely. Difficuly:Moderately Easy
1. Brush off any rust or foreign particles. Wipe flange surface thoroughly with a rag soaked in acetone or other suitable solvent to remove grease or oil. 2. Insert fingernail between the paper backing strip and the tape and strip the paper back three to six inches. Draw a reference line in flange and press squared off end of tape against it.