AWWA and Plate Steel Flanges General Information

General Information

Since the first edition of the AWWA Standard C207 was printed in 1952, AWWA flanges have commonly been used in waterworks, wastewater, slurry, plant piping, and other light duty applications. Pressure ratings for AWWA flanges range from the Class B flange rated at 86 psi to the Class F flange rated at 300 psi. The AWWA C207-01 standard describes 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 describes blind flanges. Flanges described in the AWWA C207-01 tables are intended for use with steel pipe, fittings or appurtenances meeting the requirements of ANSI/AWWA C200, ANSI/AWWA C208, ASTM A134, ASTM 139, or other equivalent standards. It is further intended that these flanges be attached by welding in accordance with AWWA C207-01 Sec.4.3.

Pressure Ratings

As per AWWA C207-01 Sec. 1.3, the pressure ratings listed for AWWA Class B, D, E and F flanges are for conditions and temperatures customary in water utility services. The pressure ratings for the flange should be based on the design of the maximum operating pressure plus the anticipated sure pressure. Test pressures should not exceed 125 percent of the ratings. Flange design is based on pressure considerations, not for stresses induced by external moments when pipe acts as a beam. The tables of the AWWA C207-01 standard have been developed using a design stress of 16,000 psi for the working pressure design.

Flange Material

As per AWWA C207-01, Sec 4.1, flanges shall be made from seamless forgings, cut from plate as a single piece, welded bar rings or segmented and welded plates as per C207-01 Sec 4.2.4.

Forgings shall meet the minimum requirements or ASTM A105 or A181.

Steel plate or bar used in the manufacture of flanges shall meet the following requirements:
1. Tensile strength = 50,000 psi (345 mpa) (min.)
2. Yield strength = 32,000 psi (221 mpa) (min.)
3. Carbon = 0.29 percent (max.)
4. Phosphorous = 0.04 percent (max.)
5. Sulfur = 0.05 percent (max.)

Plate steel designations that will meet the previously listed requirements include but are not limited to the following designation: 1. A36
2. A516, grade 60, 65, and 70

Pacific Coast Flange Inc will provide mill test reports showing conformance to the physical and chemical requirements for all flanges ordered.

Flange Facing

As per AWWA C207-01 Sec 4.2.2, all AWWA flanges shall be flat-faced without projection or raised area of face. Either a serrated concentric or serrated spiral finish having from 24 grooves per inch to 470 grooves per inch shall be used. The cutting tool employed shall have an approximate 0.06 inch or larger radius. The resultant surface finish shall have a 250 to 500-uin. roughness.

Drilling Templates

As per AWWA C207-01 Sec. 4.2.3 drilling templates are in multiples of four so that fittings can be make to face any quarter. Bolt holes shall straddle the center line, except where special mating conditions exist and shall be drilled 1/8 in. (3.2mm) larger in diameter than the nominal diameter of the bolt, except on flanges larger that 84 inches (2,100mm) diameter, bolt holes shall be drilled 3/16 inches (4.8mm) larger than the nominal bolt diameter. Bolt holes may be over drilled by an additional 1/8 in (3.2mm) to accommodate insulators or to facilitate alignment with the mating flange.