N.Y. Comp. Codes R. & Regs. tit. 12, § 14-9.13 – Safety valve construction and rating.

(a) To insure the valve being free, each safety valve shall have a substantial lifting device by which the valve disk may be positively lifted from its seat when there is at least 75 percent of full working pressure on the boiler. The lifting device shall be such that it cannot lock or hold the valve disk in lifted position when the exterior lifting force is released. Disks of safety relief valves used on high-temperature water boilers shall not be lifted while the temperature of the water exceeds 200° Fahrenheit. If it is desired to lift the valve disk to assure that it is free, this shall be done when the valve is subject cent of the set pressure. For high-temperature water boilers, the lifting mechanism shall be sealed against leakage.
(b) The seats and disks of safety valves shall be of suitable material to resist corrosion. The seat of a safety valve shall be fastened to the body of the valve in such a way that there is no possibility of the seat lifting.
(c) The spring shall be designed so that the full lift spring compression shall be no greater than 80 percent of the nominal solid deflection. The permanent set of the spring (defined as the difference between the free height and height measured 10 minutes after the spring has been compressed solid three additional times after presetting at room temperature) shall not exceed 0.5 percent of the free height.
1. (1) The spring in a safety valve or safety relief valve shall not be reset for any pressure more than five percent above or below that for which the valve is marked unless the new setting is within the spring design range established by the manufacturer or is determined to be acceptable to the manufacturer. If the set pressure is to be adjusted within the limits specified above, the adjustment shall be performed by the manufacturer, its authorized representative, or an assembler. An additional valve data tag identifying the new set pressure, capacity, and date shall be furnished and installed, and the valve shall be resealed.
2. (2) If the set pressure of a valve is changed so as to require a new spring, the spring shall be acceptable to the manufacturer. The spring installation and valve adjustment shall be performed by the manufacturer, its authorized representative, or an assembler. A new nameplate shall be furnished and installed, and the valve shall be resealed.
(d)
(e) A safety valve over three inches in size, used for pressures greater than 15 psi gage, shall have a flanged inlet connection or a welding end inlet connection. The dimensions of flanges subjected to boiler pressure shall conform to the American National Standards.
(f) When the valve casing is marked as required by section 14-9.8 of this Subpart, it shall be the guarantee by the manufacturer that the valve also conforms to the details of construction herein specified.
(g) All safety valves shall be so constructed that the failure of any part cannot obstruct the free and full discharge of steam from the valve. Safety valves shall be of the direct spring loaded pop type, with seat inclined at any angle between 45 and 90 degrees, inclusive, to the center line of the spindle. The maximum rated capacity of a safety valve shall be determined by actual steam flow at a pressure of three percent in excess of that at which the valve is set to blow, and with a blowdown in accordance with section 14-9.12 of this Subpart and credited with 90 percent of the flow developed.
(h) Safety valves may be used which give any opening up to the full discharge capacity of the area of the opening of the inlet of the valve, provided the movement of the valve is such as not to induce lifting of water in the boiler.
(i) Dead-weight or weighted-lever safety valves shall not be used.
(j) For high-temperature water boilers safety relief valves shall be used. Such valves shall have a closed bonnet. For purposes of selection the capacity rating of such safety relief valves shall be expressed in terms of actual steam flow determined on the same basis as for safety valves. In addition, the safety relief valves shall be capable of satisfactory operation when relieving water at the saturation temperature corresponding to the pressure at which the valve is set to blow.