N.Y. Comp. Codes R. & Regs. tit. 12, § 14-9.38 – Method of support.

(a) A horizontal-return tubular boiler over 72 inches in diameter shall be supported from steel hangers by the outside-suspension type of setting, independent of the boiler side walls. The hangers shall be so designed that the load is properly distributed between the rivets attaching them to the shell and so that no more than two of these rivets come in the same longitudinal line on each hanger. The distance girthwise of the boiler from the centers of the bottom rivets to the centers of the top rivets attaching the hangers shall be not less than 12 inches. The other rivets used shall be spaced evenly between these points:
(b) A horizontal-return tubular boiler, 14 feet or-more in length, or over 54 inches and up to and including 72 inches in diameter, shall be supported by the outside-suspension type of setting as specified in subdivision (a) of this section, or at four points by not less than eight steel or cast-iron lugs set in pairs. A horizontal return tubular boiler up to and including 54 inches in diameter shall be supported by the outside-suspension type of setting as specified in subdivision (a) of this section, or by not less than two steel or cast-iron lugs on each side. The distance girthwise of the boiler from the centers of the bottom rivets to the centers of the top rivets attaching the hangers shall be not less than the square of the shell diameter divided by 675. If more than four lugs are used they shall be set in four pairs, the lugs of each pair to be spaced not over two inches apart and the load to be equalized between them (see Figure P-46). If the boiler is supported on structural steel work, the steel supporting members must be so located or insulated that heat from the furnace cannot impair their strength.