MSS SP 67 Wafer Butterfly Valve | Cast Iron, Ductile Iron

Technical Drawing, Function & Advantages

The technical drawing of a MSS SP 67 wafer type butterfly valve, made of cast iron. handle/ lever operated, concentric (centerline) design, pinned disc, soft seated.

The MSS SP 67 cast iron wafer butterfly valve, either furnished with ductile iron or grey iron body, has a flangeless flat body that has a minimum face-to-face dimension, which is equal to twice the required wall thickness plus the width of the packing box. When used in piping connection, the valve will be clamped between two pipe flanges using through bolting. The MSS SP 67 wafer butterfly valve is a quarter-turn (0° to 90°) rotary-motion valve that uses a round disc as the closure member. When it is fully open (at 90° position), the disc remains parallel to the piping flow direction and extends into the pipe itself. When the valve is being closed, the disc rotates to become perpendicular to the direction of flow and acts as a dam to stop or reduce the flow. At the fully closed position (0° position), the seating surfaces of the disc rim and the rubber seat are in full contact with each other. The butterfly valve can be used not only for on-off service but also throttling service since it provides sensitive flow control when open between about 15° to 70°. Their great advantage is their narrow width and light weight, low cost, frictionless rotation that require little torque, and the simplicity of their design. Although MSS Sp 67 allows for sizes from NPS 1/2 through NPS 72, wafer type butterfly valves are more commonly applied in the specific sizes from 2″ to 12″.

Material Selection & Design Features

Ductile iron wafer type butterfly valves made in accordance with MSS SP 67.

• MSS SP 67 cast iron wafer butterfly valves shall be designed in accordance with the pressure-temperature ratings of ASME B16.1 or AWWA C504. The most commonly used material grade is ASTM A126 Grade B. MSS SP 67 ductile iron wafer butterfly valves shall be designed in accordance with the pressure-temperature ratings of ASME B16.42 or AWWA C504. The most commonly used ductile iron grades are ASTM A536 Grade 60-40-18 and Grade 65-45-12. Generally, cast grey iron butterfly valves are available in pressure ratings Class 25, Class 125 and Class 250; Cast ductile iron butterfly valves are available in pressure ratings Class 150 and Class 300.
• The disc material covers stainless steel 304 (ASTM A351 CF8), stainless steel 316 (ASTM A351 CF8M), aluminum bronze (ASTM B148 C95400 or C95800), depending on the fluid medium and environment. In water work service, the disc can be made of ductile iron plated with nickel. The disc is attached to the stem/shaft by the use of a tapered pin. The pin minimizes flow turbulence, thus improving the flow coefficient C_v. The pinned disc design also facilitates the rapid assembly of the valve as well as field maintenance.
• The centerline disc design: The centerline of the disc is in coincidence with the exact centerline of the stem. It is also known as a concentric disc or a concentric butterfly valve. With a centerline disc, where the middle of the disc and the stem are exactly centered in the valve, a portion of the disc always remains in contact with the seat regardless of the position.
• The soft-seated design: A tight shut-off can be achieved by using soft or resilient polymer seats. Because of the constant contact between the disc and seat, the seat shall be made from synthetic rubbers with good wear resistance, especially with any type of throttle applications. The rubber seat is lined in the body and extends over the end faces and act as a gasket.
• Position indicator with lock: In throttling service, the indicator can clearly indicates the exact position of the disc with lock function for precise flow control.

Dimensions

Structural dimensions for MSS SP 67 wafer type butterfly valves (cast iron or ductile iron). The drilling dimensions shall be compatible for use with flanges conforming to one of the standards: ASME B16.1 Class 25, Class 125, Class 250; ASME B16.5 Class 150 and Class 300; ASME B16.24 Class 150; ASME B16.42 Class 150 and Class 300; AWWA C207.