Rubber lined (carbon steel bodied) butterfly valves we have installed in a sulphate reducing package (sea water filtered to 5 microns with occasional acid and alkali washes).These valves have to seal against 20 bar(g) and are only 150# valves. We sent the first batch of failures off to the vendor who recommended changing the rubber spec, we installed these and they also failed, we sent these off and the vendor recommended changing to super duplex bodied high performance butterfly valves ( as they say we have solids in the system), we are purchasing some but they are very long deliveries and expensive. We have some existing hard seated triple offset stainless butterflys in the system that are also passing. As an alternative we can source some composite plastic valves which certainly should be resistant to any corrosion problems but we have never used any before. 20 bar is an awful lot for lined rubber butterfly valves. The highest-rated butterfly I know has the liner bonded to the body, and it is rated to 250 psi ( 17 bar). 20 bar is out of the ANSI 150 limitations by a hair, so you should technically use ANSI 300. The High-performance butterfly valve sounds like a better choice. Super duplex may not be necessary-my corrosion chart shows lots of reasonably common materials choices good for up to 20%wt NaCl solution at up to 212F, and Monel, Hast-C, and several others good for ANY concentration of salt in water.

MORE NEWS