(a) Every attached superheater shall have one or more safety valves near the outlet. If the superheater outlet header has a full, free, steam passage from end to end and is so constructed that steam is supplied to it at practically equal intervals throughout its length so that there is a uniform flow of steam through the superheater tubes and the header, the safety valve, or valves, may be located anywhere in the length of the header.

(b) The discharge capacity of the safety valve, or valves, on an attached superheater may be included in determining the number and size of the safety valves for the boiler, provided there are no intervening valves between the superheater safety valve and the boiler, and provided the discharge capacity of the safety valve, or valves, on the boiler, as distinct from the superheater, is at least 75 percent of the aggregate valve capacity required.

(c) Every independently fired superheater which may be shut off from the boiler and permit the superheater to become a fired pressure vessel shall have one or more safety valves having a discharge capacity equal to six pounds of steam per square foot of superheater surface measured on the side exposed to the hot gases. In the case of electrically heated superheaters, the safety valve capacity shall be based upon 3½ lb/hr/kw input. The number of safety valves installed shall be such that the total capacity is at least equal to that required.

(d) A soot-blower connection may be attached to the same outlet from the superheater that is used for the safety-valve connection.

(f) Every reheater shall have one or more safety valves, such that the total relieving capacity is at least equal to the maximum steam flow for which the reheater is designed. At least one valve shall be located in the steam flow path between the reheater outlet and the first stop valve. The location shall be suitable for the service intended and shall provide the overpressure protection required. The pressure drop upstream of each safety valve shall be considered in the determination of set pressure and relieving capacity of that valve. The relieving capacity of that valve shall be not less than 15 percent of the required total. The capacity of reheater safety valves shall not be included in the required relieving capacity for the boiler and superheater.