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.
 | 1. Ring flanges available overbored or counterbored per customer specification. 2. Bolt holes shall be drilled 1/8th inch larger in diameter than the nominal diameter of the bolt, except for flanges larger than 84 inch in diameter which shall be drilled 3/16th inch larger than the nominal diameter of the bolt. 3. Drilling same as ANSI/ASME B16.1 125 lb and B16.5 150 lb pattern. 4. Flanges available overdrilled to accommodate insulators. 5. AWWA recommends the use of dished head assemblies as alternate to blind flanges, sizes over 72" nominal. 6. AWWA C207-01 Class B and D Hub Flanges are identical to Industry Standard Class 125 Light Weight Flanges. |
