In an industrial process gaskets are often considered to be a commodity which is purchased at the lowest price, fitted by anyone working on plant maintenance, irrespective of what training they have been given, and forgotten. Also, with the downsizing that has taken place in industry, that body of expertise on matters to do with gaskets and their use that resided in the long service maintenance and design personnel has tended to be lost. On both counts these trends can lead to an unplanned shutdown and the loss of production that far outweighs the cost of the gasket which caused the problem.
In extreme chemical services the gasket solution has often been PTFE but now there are forms of processed PTFE, biaxially orientated, that offer superb security against the previously relevant concerns about creep and blowout. Until recently, following the appreciation that graphite has a far lower temperature capability than previously thought, there have not been any viable high temperature, high pressure alternatives to asbestos but with the advent of sealing materials and gaskets based upon vermiculite that is no longer true. These gaskets are in service to above 900oC and have excellent chemical resistance with total freedom from the oxidation that occurs with graphite.
Flexitallic Limited is based in Cleckheaton, West Yorkshire, UK. " target="_blank">www.flexitallic.com