Rectangular Rubber Seated Butterfly Valves Spec Sheet:
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All rectangular butterfly valves shall be rubber seated and shall be____in height and ____in width. They shall be bubble tight at rated pressures with flow in either direction. Valve design shall be suitable for maximum operating pressure differential of 10 psig. They shall be capable of valve operation after long periods of inactivity. Valve discs shall rotate 90 degrees from the full open position to the tight shut position. When subjected to the maximum design head, a stress safety factor of 3.0 on the yield point or 5.0 on ultimate strength, whichever is the lower, shall not be exceeded. Maximum deflection of the valve structural design limit shall be 1/32". Because of the nature of the service, experimental units or developmental designs will not be allowed. Bidders shall demonstrate a minimum of 5 years successful operation in installations and shall submit a list of such installations upon request. Valves shall be as manufactured by the Henry Pratt Company.
Valve Bodies and Flanges
The valve body shall be a rectangular fabrication of carbon steel. Upper trunnion shall be recessed bored for Chevron packing. Valve bodies shall be designed for wall mounting to existing wall thimble or jack bolt mounting.
The valve disc shall be fabricated of carbon steel with a stainless steel seating edge. Seating edge shall be 18-8 Type 304 stainless steel and shall be ground, polished and contoured. Leakage at corners under specified conditions or tests shall be cause for rejection. Disc shall be streamlined in shape to prevent turbulence in the full open position and to minimize pressure drop across valve. Exposed disc rib stiffeners are not acceptable.
The valve seat shall be contained in the body of the valve. Retaining segment and retaining screws shall be of 18-8 Type 304 stainless steel. The seat shall be a synthetic rubber compound with a durometer of 50. Seat adjustment possible and inherent in the design shall not be less than 1/8 inch. Valve seats shall be fully field adjustable and replaceable without dismantling operator, disc or shaft. The valve manufacturer shall certify that the rubber seat is fully field adjustable and replaceable.
Valve shafts shall be the stub type with shafts extending into the disc for a minimum distance of at least 1.5 shaft diameters. Shafts shall be securely locked to the disc by stainless steel taper pins. Shaft material shall be 18-8, Type 304 stainless steel.
Main shaft bearings shall be teflon, fiberglass backed sleeve type fitted into each valve body trunnion bore. Unit bearing stress shall not exceed 4000 psi. Each valve assembly shall be furnished with a 2-way thrust bearing assembly designed to hold the disc centered in the valve seat at all times. Thrust bearing shall be secured by locking device and easily accessible for field adjustment from actuator end of the valve.
Valves designed for channel installation shall be installed to provide a means of removing the complete valve assembly without dismantling the valve or actuator. Installation methods that employ permanent, multiple bolting shall not be acceptable for channel mounting. Valves designed for wall mounting shall have flanges drilled in accordance with the template of a frame or casting to which it is bolted. Valves installed in ducting shall have body flanges suitable for welding to steel ducting or drilled for bolting to duct flanges.Painting: Two coats of paint shall be applied to the inside and outside surfaces of the valve body and the outside surfaces of the disc, except finished surfaces, bearing surfaces and the stainless steel seat retainers and disc edge. The paint shall be either asphalt varnish (per Federal Specifications TT-C494A) for sewage service or where additional protection is desired. Rust inhibitive alkyd primer shall be applied for fresh water, steam or air service.