Non-linear finite element modelling and analysis of the effect of gasket creep-relaxation on circular bolted flange connections

• Published in: The International journal of pressure vessels and piping 2017-02, Vol.150, p.52-61
• Main Authors: Luyt, P.C.B., Theron, N.J., Pietra, F.
• Format: Article
• Language: English
• Subjects: Bolt tightening increments; Contact pressure; Flat face flange; Gasket creep-relaxation; Raised face flange
• ISSN: 0308-0161; 1879-3541
• DOI: 10.1016/j.ijpvp.2016.12.001

It is well known that gasket creep-relaxation results in a reduction of contact pressure between the surface of a gasket and the face of a flange over an extended period of time. This reduction may result in the subsequent failure of the circular bolted flange connection due to leakage. In this paper a pair of flat and raised face integral flanges, PN 10 DN 50 (in accordance with the European EN 1092-1 standard), with non-asbestos compressed fibre ring gaskets with aramid and a nitrile rubber binder were considered. Finite element modelling and analyses were done, for both the circular bolted flange configurations, during the seating condition. The results of the finite element analyses were experimentally validated. It was found that the number of bolt tightening increments as well as the time between the bolt tightening increments had a significant impact on the effect which gasket creep-relaxation had after the seating condition. An increase in either the number of bolting increments or the time between the bolting increments will reduce the effect which gasket creep-relaxation has once the bolts had been fastened. Based on these results it is possible to develop an optimisation scheme to minimize the effect which gasket creep-relaxation has on the contact pressure between the face of the flange and the gasket, after seating, by either increasing or decreasing the number of bolt tightening increments or the time between the bolt tightening increments. •Number of bolt tightening increments and time between bolt tightening increments had significant impact on effect of gasket creep-relaxation after the seating condition.•Impact of gasket creep-relaxation during seating and operating phases investigated by means of finite element analysis and experimentally verified.•Possible to develop optimisation scheme to minimize effect ofh gasket creep-relaxation on contact pressure between flange face and gasket.•Knowing the contact pressure is crucial when designing large diameter flanges that fall outside the designs prescribed by commonly accepted flange codes.