This standard covers two types of slip-on flanges, ring type and hub type, that may be used interchangeably if the dimensions given in the standard are used. The standard also covers blind flanges. The flange types and the tables that describe them are: Ring-type, slip-on flanges (Tables 2, 5, and 6); Hub-type, slip-on flanges (Tables 3 and 4); and Blind flanges (Table 7). Unless otherwise specified by the purchaser, the manufacturer of pipe fittings will select the type to be used. The purpose of this standard is to provide purchasers and manufacturers minimum material requirements and dimensions for a variety of steel flanges for attachment to steel water pipe and fittings.
Both the AWWA and ANSI have thorough standards for flanges, and the two standards are different in several ways. AWWA standards provide flange properties intended for potable water use only. In contrast, ANSI standards are aimed at industrial flange applications. For example, AWWA flange ratings are applicable only at atmospheric temperature, while ANSI ratings cover flange installations from -20°F to 1500°F.
ANSI covers numbered class flanges from 150 to 2500, and AWWA standards encompass lettered flange classes B, E, F, and the commonly used class D connection. AWWA provides ratings for a much broader range of nominal pipe sizes (3″-144″) than ANSI provides (1/2″-24″).
Finally, ANSI and AWWA flange standards differ in the breadth of applications discussed. ANSI includes information for welded auxiliary connections and tapping, while AWWA does not address those installations. Also, the AWWA standard only encompasses ring, hub type, blind flanges, and threaded iron flanges while the ANSI standard inlcudes all flange types.
This discussion on AWWA flange standards and ANSI flange standards is based on information from ANSI/AWWA C115/A21.15-99: “American National Standard for Flanged Ductile-Iron Pipe with Ductile-Iron or Gray-Iron Threaded Flanges”, ANSI/AWWA C207-94: “AWWA Standard for Steel Pipe Flanges for Waterworks Service-Sizes 4 In. Through 144 In.”, and ANSI B16.5-1981: “Pipe Flanges and Flanged Fittings”.