Trade.Information

Product Name: Air / Vacuum Valves

Product Description

Air / Vacuum Valves perform two important functions when mounted at high points on pipelines. First of all, they allow large quantities of air within the line to be exhausted as that line is being filled. When the air has been vented and the fluid level reaches the air / vacuum valve, the float rises and seals tightly against a synthetic seat. Secondly, in the event of the line being drained, either intentionally or through a fracture in the system, the air / vacuum valve responds to the loss of pressure and opens. This allows air to re-enter the pipeline and prevents a potentially damaging vacuum from developing. Specifications: - Scope 1.1 This specification is intended to cover the design, manufacture, and testing of 1/2 in. (13 mm) through 20 in. (500 mm) Air/Vacuum Valves suitable for pressures up to 740 psig (5100 kPa) clean or raw water service. 1.2 Air/Vacuum valves shall be fully automatic float operated valves designed to exhaust large quantities of air during the filling of a piping system and close upon liquid entry. The valve shall re-open during draining or if a negative pressure occurs. [NOTE: See Air Release Valves for releasing air during system operation and Combination Air Valves for both air release and air/vacuum functions.] Connections 2.1 Valve sizes 3 in. (76 mm) and smaller shall have full size NPT inlets and outlets equal to the nominal valve size. The body inlet connection shall be hexagonal for a wrench connection. 2.2 Valve sizes 4 in. (100 mm) and larger shall have bolted flange inlets with threaded or plain outlets and protective hoods to prevent debris from entering the valve. Flanges shall be in accordance with ANSI B16.1 for Class 125 or Class 250 iron flanges and ANSI B16.5 for Class 150 or Class 300 steel flanges. 2.3 The valve shall have two additional NPT connections for the addition of Air Release Valves, gauges, testing, and draining. Design 3.1 The valve body shall provide a through flow area equal to the nominal valve size. A bolted cover with alloy screws and flat gasket shall be provided to allow for maintenance and repair. 3.2 Floats shall be unconditionally guaranteed against failure including pressure surges. The float shall have a hexagonal guide shaft supported in the body by circular bushings to prevent binding from debris. The float shall be protected against direct water impact by an internal baffle. 3.3 The resilient seat shall provide drop tight shut off to the full valve pressure rating. The seat shall be a minimum of .5 in. (12 mm) thick on 2 in. (50 mm) and larger valves and secured in such a manner as to prevent distortion. Valves with working pressures above 400 psig (2760 kPa) shall have metal seats with synthetic seals. 3.4 On valve sizes 4 in. (100 mm) and larger, the cover shall be fitted to the valve body by means of a machined register to maintain concentricity between the top and bottom guide bushings at all times. The float shall be double guided with a guide shaft extending through the float to prevent any contact with the body. A resilient bumper shall be provided to cushion the float during sudden opening conditions. Materials 4.1 The valve body, cover, and baffle shall be constructed of ASTM A126 Class B cast iron for Class 125 and Class 250 valves. Class 300 ductile iron valves shall be constructed of ASTM A536 Grade 65-45-12 ductile iron. Class 300 steel valves shall be constructed of ASTM A216 Grade WCB cast steel. 4.2 The float, guide shafts, and bushings shall be constructed of Type 316 Stainless Steel. Non-metallic guides and bushings are not acceptable. Resilient seats shall be Buna-N. Class 300 steel valves shall have a 316 Stainless Steel Seat with Buna- N seal to provide an initial contact to Buna-N with final metal to metal contact to prevent over compression of the resilient seal.