It is evident that metal sealed butterfly valve can perform many of the functions previously carried out by gate and ball valves at a much lower cost and with a considerable weight saving. This is demonstrated by the increasing use of metal sealed valves in the applications previously specified for gate and ball valves. The triple offset version of the metal sealed butterfly valve has many advantages over other types which rely on seat or seal deformation; those with field replaceable seat and seal have that further advantage. As with any valve selection, the correct choice is dependent on many factors and it would not be cost effective to specify a metal sealed butterfly valve when a cheaper, elastomeric or PTFE sealed valve is adequate for the duty. However, the metal sealed, and in particular the triple offset design, is the correct choice when high reliability sealing is required, particularly at high/low temperatures and high pressures.
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