Exchanger flange leaks are a major environmental, safety, and economic concern. Flange leaks are generally caused by one or more of the following:
Wrong Gasket Selection
• Gasket is too wide, there is not enough bolting to properly compress the gasket.
• Gasket is too narrow, causing gasket alignment and seating problems.
• Gasket seating surface is not compatible with the gasket. It can be either too smooth for gaskets such as composition asbestos, or too rough for gaskets such as solid metal or metal jacketed.
• Gasket is the wrong material for the application (i.e., stock, temperature, and pressure.)
Poor Flange Design
• Flanges do not have enough thickness to withstand the operating and hydrostatic test pressures without leaking.
• Bolts have been torqued past their maximum stress in trying to stop leaks.
• Flanges were deformed or rotated in the process of trying to stop leaks. This causes improper gasket seating and is indicated by a gasket that is substantially thinner on the outside diameter than on the inside diameter.
• Flanges do not mate up well initially.
Figure 1000-1 illustrates the gasket seating problems related to flanges that are not aligned properly or are rotated.
• Rain storms can deform uninsulated flanges and unseat the gasket.
• Gasket was damaged during installation.
• Flange surface was scratched or gouged during maintenance.
• Poor torquing procedure caused uneven compression of the gasket around its circumference.
• Flange is so extensively corroded there is not enough gasket seating surface left.
• Gasket material is not resistant to the process fluid.
• Excessive temperatures or pressure surges can unseat the gasket and stretch the bolts.