Standard flange facings

Fig. 12.7. American Standard flange facings (168). (Courtesy of Taylor Forge ond Pipe Works.)...

Strainers of this type are normally designed with standard flange faces so that they can be fitted at a suitable flange joint in the pipeline. When removed they can be replaced by a spacer washer. These filters may take the form of a flat disc or a conical basket - some types of strainer basket are shown in Figure 3.1. Flat disc strainers are normally perforated plates, while basket strainers may be of perforated plate or supported wire mesh. Basket strainers can have a higher dirt capacity. 

Many potential variations exist on these simple themes. For example, the high capacity pumping station used in our laboratory can be connected to any of five different vacuum lines by attaching standard flanges to an octahedral cross welded to the face plate flange bolted to the diffusion pump. Similar variations are possible with glass systems fitted with the appropriate hardware. 

Standard flanges arc available with a variely of machined faces, as shown in Fig. 12.7 (corresponding dimensions are given in Table 12.2). 

Valve bodies are also standardized to mate with common piping connections flanged, butt-weld end, socket-weld end, and screwed end. Dimensional information for some of these joints and class pressure-temperature ratings are included in Sec. 10, Process Plant Piping. Control valves have their own standardized face-to-face dimensions that are governed by ISA Standards S75.03, 04, 12, 14, 15, 16, 20, and 22. Butterfly valves are also governed by API 609 and Manufacturers Standardization Society (MSS) SP-67 and 68. 

For flanges of nonstandard dimensions or for sizes beyond the scope of the approved standards, design shall be in accordance with the requirements of the ASME Boiler and Pressure Vessel Code, Sec. T11, except that requirements for fabrication, assembly, inspection testing, and the pressure and temperature hmits for materials of the Piping Code are to prevail. Countermoment flanges of flat face or otherwise providing a reaction outside the bolt circle are permitted if... 

API Standard 526, Flanged Steel Pressure Relief Valves This is a purchase specification for flanged steel PRVs. Basic requirements, such as orifice designations and area, materials, pressure-temperature limits and centre-to-face dimensions, inlet and outlet, are given for both spring-operated and pilot-operated PRVs (Figure 4.13). 

For 2-inch and larger gate valves, use 150-pound ANSI standard cast, carbon steel, flanged, OS Y, 11-13% chrome stainless steel trim, 1/16-inch raised face. For condensate service use 125-pound ANSI standard cast iron, flanged OS Y brass trim, and stem. 

For 2-inch to 4-inch size plug valves, specify 300-pound ANSI standard cast carbon-steel, flanged 1/16-inch raised-face, wrench operated, lubricated plug valves. 

Larger discounts are usually available on plug valves than on gate valves, so a direct comparison of the base prices would not be reliable. The base price shown represents raised face, flanged-end, cast steel valves with standard trim conforming to API 600. Ring joints on gate valves would cost approximately 40 to 50 extra. 

The standard includes nominal values (flange diameters) of between 25 and 160 mm. A considerable differentiating feature of the various types is the width of the positioning face. Whereas types A, C, and E have a narrow positioning face, B, D, and F have wide ones. The most common type is A according to ISO 12164 type E was specially developed for high-speed cutting (Fig. 3). 

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