Wafer type butterfly valves are common choice of valves in sea water services in the Norwegian offshore industry for on/off and sometimes throttling applications. The reason for selecting wafer type butterfly instead of ball or globe type valves is the cost, Weight and space saving. Wafer type butterfly valves based on API 609 standard are flangeless with very thin body and the light disk. The importance of cost saving is because of expensive exotic materials like 25Cr super duplex and titanium which are typically used for valve and piping systems in the sea water services in Norway. Whereas Graphite is the frequent choice of packing for butterfly valves, there are always engineering and metallurgical discussions about corrosion issues associated with graphite in the sea water services. This article aims to describe briefly corrosion, problems related to graphite packing in the sea water services and different solutions to avoid the issues.
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