Rigidity, positioning and surface smoothness


Rigidity_positioning and surface smoothnessž

A flange rigidity critically influences the required minimum surface pressure at mid-point between two bolts of a flanged joint. It also very much influences the type of a gasket suitable for the said joint. Where adequate bending rigidity is maintained, soft gasket materials and non-curing liquid gaskets can be used.

When deciding which of the gasketing options is suitable for your design, apart from flange rigidity, you must also look into the required / possible bolt spacing and positioning and the resulting stress distribution. Each of these factors are inevitably influencing each other and your selection of gasket material.

With conventional gaskets, surface finish or surface texture is an additional crucial factor, since the initial compressive load required to deform the gasket into the flange surface irregularities increases with rougher surface finish. Although it’s not to be completely neglected, the surface finish becomes much less important when using a liquid gasket material. For details you can consult the Gasketing design guide which I’m happy to share on request.

When talking about liquid gasket materials, there are several types depending on application method, curing method and timing or technology.

  • FIP (Formed-In-Place) Gaskets are formed by the application of a bead or by screen printing of sealant, which is then assembled in the uncured state.
  • CIP (Cured-In-Place) Gaskets are formed by the application of a bead of elastomer to one flange that is cured before the flanges are assembled. The gasket is then compressed by the mating flange to form the seal.
  • IIP (Injected-In-Place) Gaskets are liquid gaskets that are injected, after the assembly of the joint, into a groove between the two flange faces and then cured.
  • MIP (Moulded-In-Place) Gaskets are moulded directly onto one of the mating parts, usually into a groove.

I’ll go into the details of each and their advantages and recommended application areas in the next article.