A21.51-1976 (C151-76): American National Standard for Ductile-Iron Pipe, Centrifugally Cast in Metal Molds or Sand-Lined Molds, for Water or Other Liquids (PDF)

Major revisions include the following: an additional minus tolerance of 0.02 in. is permitted along the barrel of the pipe for a distance not to exceed 12 inches; the weight tolerance permitted for any single pipe is 6% for pipe 12 in. or smaller and 5% for pipe larger than 12 inches; and, the tables include data for the five standard laying conditions covered in A21.50-1976. Types 1, 2, and 3 replace A, B, and 5, respectively, and in A21.51-1971, Types 3 and 4 have been added to provide a wider selection of laying conditions; the pipe thickness selection tables have been revised to reflect the changes in the 1976 edition of A21.50, the standard for thickness design of ductile-iron pipe; the standard thickness classes have been renumbered - Class 1 becomes Class 51; Class 2 becomes Class 52; and so on; Class 50 has been added for 6-54 in. pipe, and Class 51 has been added for 3-12 in. pipe; pipe weights have been adjusted for 3-24 in. push-on joint pipe to reflect lighter bell weights based on push-on joint bells, which are more compatible with the barrel thicknesses of ductile-iron pipe; and, Table 3 has been added to show rated working pressure and maximum depth of cover of the standard laying conditions and standard thickness classes.