scope:

a. This standard established certain standard dimensions for heater tubes and for cast or wrought headers.

b. For tubes, standard sizes and lengths are established. Tube wall thickness is not within the scope of this standard.

c. For headers, only center-to-center dimensions and tubeseat details are established. These dimensions are applicable only to manufacturers' standard header pressure ratings not exceeding 850 lb nominal.

d. For tubes, tolerances for size and length are not included herein, but shall be specified by the purchase order. This may be done by reference to an ASTM * or other applicable specification. If a tube for rolled attachment to a header is purchases with size (outside diameter) tolerance as ordinarily applicable to pipe (as by reference to an ASTM specification for "pipe"), the user is cautioned that difficulty may be experienced in properly fitting the tube into the header.

e. For headers, tolerances on center-to-center and for tubeseat bore and depth of groove are included. Other tolerances shall be the manufacturer's standard.

* American Society for Testing Materials, 1916 Race St., Philadelphia 3, Pa.