"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."
API STD 630-1961 history
1961API STD 630-1961 TUBE AND HEADER DIMENSIONS FOR FIRED HEATERS FOR REFINERY SERVICES (Second Edition)
1959API STD 630-1959 TUBE DIMENSIONS FOR FIRED HEATERS (First Edition)