Many leaks that occur on bolted flanges are often initially ascribed to the gasket as the probable source of the leak. However, in many cases, leaks are not due to gasket performance or failure, but to factors other than the gasket itself. This blog highlights some of these common causes of leaks in bolted flange connections, and offers a guide to troubleshooting the source of leaks when they occur.
Common Causes of Leaks
Gasket failure is one of the many reasons why a bolted flange connection may leak. Often, this is due to corrosion and degradation of the gasket material by chemical attack. Other common causes of leaks in bolted flange connections include the following:
Under-loading of the gasket
Gaskets must be sufficiently compressed to achieve a leak-free seal. Application of insufficient compressive load on the gasket may lead to joint leakage. Often, under-loading occurs because the gasket material selected may be too hard or of insufficient thickness. In these cases, gaskets consisting of a softer material or greater thickness should be chosen. In all cases, compressive loading should be done to the gasket manufacturer’s recommended values.
Over-loading of the gasket
Applying too much compressive load to a gasket may result in splitting or crushing of the gasket face. Often, this is done in the misguided notion that further tightening of joint fasteners will reduce or prevent a leak. Again, following the gasket manufacturer’s recommended compressive load is the best policy. In those cases where a gasket cannot bear the load required, a gasket with better load-carrying capacity should be selected.
Re-use of a previously used gasket
Gaskets are often reused in an attempt to save costs. This often occurs after routine maintenance inspections of bolted flanges, where visual inspection of a gasket may reveal little apparent wear and tear. What visual inspection cannot reveal, however, is hardening and loss of deformability and recoverability – factors that may seriously compromise the gasket’s ability to provide leak-free service should it be reused. Since the cost of using a new gasket is relatively small, safety and performance should never be compromised by reusing a gasket. The best policy, to ensure safety and performance, is to install a new gasket following every maintenance inspection.
Poor installation of the gasket and torquing of fasteners
When installing gaskets, it is important to seat the gasket correctly in the joint and use a properly calibrated torque wrench to tighten fasteners. All reputable gasket manufacturers can provide a torque table showing the optimal torque values for each style of gasket. Each type of gasket material has its own unique torque values, and the specified torque value should be implemented equally, in increments of one-third at a time. Bolt-down of the gasket should be done in stages, with torque applied to fasteners incrementally, following a cross or star tightening pattern. You can find more information on how to correctly install and torque a new gasket in our blog The Correct Procedure for Gasket Installation.
At CRGI, we are committed to providing the finest gaskets available for every sealing application. All gaskets we produce and supply are fabricated from highest-quality materials, including those from Teadit, American Biltrite, and other leading providers. All gaskets we supply are precision-manufactured to exacting specifications and tolerances on the latest cutting technology. No order is too small or large, and we specialize in ultra-fast lead times and emergency service.
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