Choosing the right gasket
When choosing the best sealing solution you must take into consideration the following criteria:
- The operating parameters – temperature, pressure, media;
- Fasteners, flange type and sealing surfaces, bolts, geometry, materials;
- Standards – environmental and regulatory requirements
- The human factor – assembly norms and assembly personnel competencies;
The operating parameters will be the starting point in choosing the gasket. Gasket materials and its construction should be chosen to withstand the pressures exerted against the gasket, to maintain the parameters to ensure maximum performance throughout the temperature range at which it will be exposed and to withstand corrosive attack of the sealed medium.
Flange geometry is decisive in choosing the type of gasket to be used. Also, the type and material of the fasteners may require low torques levels, in this case being used gaskets designed to ensure the required level of tightness at low surface stresses. On the other hand, high pressure metal flanges require the use of resilient gasket materials to withstand both internal pressures and high surface stresses needed to maintain tightness. Also, sealing surface roughness can influence gasket thickness. The surface finish of the flange faces has a major impact on the performance, especially in metal-to-metal contact. All these factors must be considered when choosing the gasket.
Depending on the industry they belong, applications must comply at existing norms, such as ASME B16.20, EN 12560, EN 1514, which regulate construction, materials, dimensions, thus easing the choice of the gasket. Also, there may be internal regulations which impose the use of certain material or certain types of gaskets. In addition, environmental regulations which impose a certain level of emission may be in force, therefor we must ensure that we choose gaskets certified to meet all the requirements.
The incorrect installation of the gasket is the most common cause of joint failure. All of the above consideration for choosing the right gasket may be in vain if it is not installed correctly. Currently there are approved 2 norms regulating the qualification of personnel competency in the assembly of the bolted connections of critical service pressurized system: EN 1591-4:2014 si ASME PCC-1—2013 Appendix A.