AWWA C504 Rubber Seated Butterfly Valves

The AWWA C504 rubber seated butterfly valve is a valve that uses a disc rotatable through an angle of approximately 90° as a closure member. The valve is closed when the edge of the disc is perpendicular to the flow way, open when parallel to the flow way, or used for throttling when positioned between open and closed. It has a rubber ring around the outside edge of the valve disc or the inside of the valve body to affect a seal against the metal seating surface when the disc is closed. Rubber seated butterfly valves manufactured to AWWA C504 have gained increased acceptance for use in water treatment plants and water supply and distribution lines because (1) they provide tight shutoff; (2) are relatively easy to operated, even with large pressure differentials across the valves; and (3) require relatively little space for installation.

Application Conditions

AWWA C504 rubber seated butterfly valves are available in sizes 3″ (DN80) through 72″ (DN1800), with various body and end types. The are designed for raw water, potable water, wastewater, and reclaimed water having a PH range from 6-12 and a temperature range from 33°-125°F (0.6°-52°C). They are suitable for a maximum steady-state fluid working pressure of up to 250 psig (1723 kPa), a maximum steady-state differential pressure of up to 250 psi (1723 kPa), and a maximum full open fluid velocity of up to 16 ft/sec (4.9 m/sec) based on nominal valve size.

Classifications

AWWA C504 rubber seated butterfly valves, concentric type, double-split shaft, in assembly process, 52″ 250psi, supplied to Manama, Bahrain.

According to AWWA C504, rubber seated butterfly valves can be classified in accordance with its body construction into 4 types: wafer, short-body flanged, long-body flanged, and mechanical-joint-end. The short-body flanged type is most commonly used in waterworks engineering. AWWA C504 wafer or long-body flanged butterfly valves are hardly used. When mechanical joint ends apply, they shall be furnished in accordance with ANSI/AWWA C111/A21.11. Moreover, AWWA C504 flanged butterfly valves supplied by Metalsin Tech can be classified into concentric type, single eccentric type, and double eccentric type according to the center-line arrangement of valve body, shaft and disc. They can also be classified according to the design of shaft (stem): pinned shaft, pinless shaft, single shaft, or double shaft.

Main Parts & Material Selection

The AWWA C504 rubber seated butterfly valve consists of the following main parts:

• Body: The primary pressure-retaining structure of the butterfly valve that forms a portion of the pipeline and that ends adapted for connection to the piping.
• Shaft: A bar extending through the body hubs and into the disc to support the disc and transmit operating torque to the disc-closure member.
• Disc: The closure member that is positioned in the flow stream to permit flow or to obstruct flow depending on closure position and that rotates through an angle of 90° from full open to full shut off.
• Actuator: A device attached to the valve for the purposed of rotating the valve disc to an open, closed, or intermediate position; preventing disc over-travel; and maintaining the disc in any position. The actuator any be either a handwheel, handle, pneumatic/hydraulic cylinder, worm gearbox, or electric actuator.
•  Bearing: the cylindrical journal located in the body hubs that is used to support the valve shaft and transmit disc forces to the valve body while minimizing friction and wear.
• O-ring seal: A type of seal consisting of an elastomer in the shape of a circular shape with a circular cross section.
• Rubber seat: A rubber ring around the outside edge of the valve disc or the inside of the valve body to effect a seal against the metal seating surface when the disc is closed.

The AWWA C504 double eccentric butterfly valve supplied to a waterworks project in Peru. 30″  ductile iron, EPDM rubber seated, electric actuator operated.

The valve body may be made from: (1) Gray iron of ASTM A126 Class B, or ASTM A48 Class 40; (2) Ductile iron of ASTM A536 Grade 65-45-12 and ASTM A395 Grade 60-40-18; (3) Alloy grain iron of ASTM A436 and ASTM A439; (4) Cast steel of ASTM A216 WCB; (5) Cast stainless steel of ASTM A743 CF8 or CF8M. The disc and shaft may be made from corrosion-resistant metals such as SS 410, SS 420, SS 304, SS 316, nickel-copper alloy, brass, and bronze. The rubber seats shall be applied to either the body or the disc, be of natural rubber or synthetic rubber (EPDM, BUNA-N/NBR, Viton/FPM), and permitted to be lined by PTFE. The manual actuator (a handle or handwheel) may be made from cast iron or ductile iron, or aluminum.

Coating & Testing

Both the interior and exterior surfaces of AWWA C504 rubber seated butterfly valves shall be workshop coated with an epoxy coating conforming to the requirements of AWWA C550 to a minimum dry film thickness of 8 mil and, shall be NSF/ANSI 61 approved. Performance tests shall be carried out three times to ensure the valve’s normal actuation in work. All the butterfly valves shall be subject to leakage tests to ensure a tight seal, in which the test pressure shall be 1.1 times the rated pressure. The valve bodies shall be subjected to hydrostatic test in which an internal work pressure equivalent to twice the rated pressure shall apply. The proof-of-design test shall also be conducted to demonstrate the adequacy of each basic type of valve.