Wafer

Marine wafer butterfly valves are used for isolation and basic flow control in shipboard piping systems where short face-to-face length and between-flange installation are important to the pipe layout. The wafer body is installed between mating flanges without a full lugged or double-flanged body, reducing installation length compared with double-flanged butterfly valves. Valve selection should be based on flange rating, process media, operating temperature, differential pressure, operating torque, and seat-disc compatibility with the marine environment.

This category includes the Alfa Europe S57 wafer butterfly valve, with wafer-type flange mounting, bonded liner, and face-to-face dimensions according to EN 558-1 Series 20. The stated size range is DN40 to DN1200, with flange compatibility for DIN PN6, PN10, PN16, PN25, ANSI B16.5 Class 150, and JIS B2211 5K/10K. The declared temperature range is -40 to +250 °C, provided the seat material and other elastomeric components are suitable for the actual service conditions.

Available body materials include EN-JS 1030 ductile iron, stainless steel 1.4408, ASTM A216 WCB, and aluminium bronze BS 1400 AB2. For marine duty, aluminium bronze is commonly considered for seawater circuits because of its resistance to seawater corrosion, while ductile iron and WCB require appropriate coating systems and confirmation of media compatibility. An NBR seat is suitable for selected water, air, and oil services, but should not be treated as a universal option for elevated temperature duty or chemically aggressive fluids.

During installation, checks should include flange alignment, unobstructed disc rotation, actuator or lever orientation, corrosion risk in the seat area, and wear caused by suspended solids. Where the valve is used for throttling rather than simple on-off isolation, assessment should include opening angle, flow velocity, and differential pressure, since these parameters affect noise, vibration, cavitation risk, and seat life. Maintenance planning should also consider shut-off class, leakage rate, and seat replacement requirements over the service interval.