Gasket selection requires examination of three basic elements, namely:

• The medium being sealed
• Temperature and pressure influences
• The construction of the flange where the gasket will be fitted

Determining the material which can be used to the best effect, must ensure that what is being sealed will not cause gasket degradation and be able to conform to flange irregularities without physical distortions to the flange.

CORKRUBBER AND RUBBER
Used for sealing oils, air and water at low bolt loads. Service is seen in the heavy electrical industry in transformers and switchgear. Cork rubber has a good resistance to oil at 80-100°C and is resistant to the effects of climate. Many applications ranging from gearboxes, inspection covers to water piping gaskets use rubber or CorkRubber.

NON-ASBESTOS COMPOSITES
With the demand for ever increasing pressures and temperatures, asbestos jointing is now being replaced by non-asbestos composites and can be used for high temperatures and pressures.

FELT AND SPONGES
Used for dust or very low pressure sealing. Felts are sometimes impregnated with oils or wax to include lubrication properties. Sponges are used for a variety of low pressure seals/dust covers and even in cord form for ease of installation. It is also common for sponge gaskets to be supplied with a peel off self adhesive backing.

ENGINEERING PAPERS AND SHIMS
Still providing good service are the engineering papers used where high flange loads are available but low pressure is evident i.e. gear boxes. Shims in plastic are coloured to positively identify the precise thickness to allow for accurate settings.