What is Pressure Class Ductile Iron Pipe?

Pressure Class designations were incorporated in the 1991 revision to the ANSI/AWWA C150/A21.50 design standard for Ductile Iron Pipe. This raises questions from some utilities and engineers that have in the past specified Ductile Iron Pipe based on the Thickness Class designation. Pressure Class designations refer to the pipe’s ability to hold pressure, whereas Thickness Class refers only to wall thickness, with no correlation to pressure rating. The same conservative design approach for determining wall thickness is used in determining Pressure Class criteria, which includes both service allowance and casting tolerance safety factors. The result of this conservative design approach is a Pressure Class Ductile Iron product superior to alternative pressure class materials.

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