Abstract
With the increasing concern over asbestos, more companies are considering the possibility of changing to asbestos-free, non-metallic gaskets. However, caution should be exercised when adopting alternative materials because their applicational requirements are significantly different. Specifically, when compared with premium quality compressed asbestos fibre grades, the calendered asbestos-free grades generally have: lower temperature and pressure ratings, temperature and pressure ratings which do not co-exist (that is as the temperature increases, the maximum internal pressure sealable decreases), higher minimum surface stress requirements, lower maximum surface stress values, lower creep resistance, different chemical resistance, poorer performance in steam and less tolerance to the deleterious effects of jointing compounds.
This paper attempts to demonstrate why this new group of materials should not be considered as a direct replacement for compressed asbestos fibre but rather as a limited substitute. It also offers some hope for the future with the prediction of the development of a calendered asbestos-free grade with similar properties to the best traditional asbestos-based grades but without the large cost penalty involved in selecting exfoliated graphite.
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