N.Y. Comp. Codes R. & Regs. tit. 12, § 4-5.2
(a) Capacity.
A low pressure steam boiler shall include a safety valve or valves of a capacity such that with the heat generating equipment operating at maximum, the steam pressure shall not rise more than five psi gage above the maximum allowable working pressure with all valves open. If the minimum valve capacity in pounds per hour is calculated it shall be determined by dividing by 1,000 the maximum Btu output at the boiler nozzle obtainable from the heat generating equipment, or by multiplying the square feet of heating surface by the values given in the following table:
Minimum pounds of steam per hour per square foot of surface
| Boiled heating surface | ||||||
|---|---|---|---|---|---|---|
| Hand-fired | Stoker-fired | Oil, gas, or pulverized-fuel-fired | Hand-fired | Stoker-fired | Oil, gas, or pulverized-fuel-fired | |
| Fire-tube boilers | 5 | 7 | 8 | 8 | 10 | 14 |
| Water-tube boilers | 6 | 8 | 10 | 8 | 12 | 16 |
Note:
When a boiler is fired only by a gas having a heat value not in excess of 200 Btu per cubic foot, the minimum safety valve relieving capacity may be based on the values given for hand-fired boilers above.
The minimum capacity of the valve or valves shall be governed by the capacity marking on the boiler.
(b) Increased capacity.
When operating conditions are changed or additional boiler heating surfaces installed, the valve capacity shall be checked and increased if necessary to meet the new conditions. Necessary additional valves may be installed on the outlet piping, providing there is no intervening valve nor any other branching pipes between the additional valves and the boiler.
(c) Accumulation test.
If the total capacity of safety valves is not otherwise ascertained they shall be subjected to an accumulation test.
(d) Type.
Required safety valves shall be of the spring-pop type, adjusted and sealed to discharge at a pressure not to exceed 15 psi gage. The seats and disks shall be of suitable material to resist corrosion.
(e) Size.
No safety valve for a low pressure steam heating boiler shall be smaller than ¾ inch except in case the boiler and radiating surfaces are a self-contained unit. No safety valve shall be larger than 4½inches. The inlet opening shall have an inside diameter equal to or greater than the seat diameter.
(f) Lifting device.
Each safety valve for a low pressure steam heating boiler shall have a substantial device which will positively lift the disk from its seat at least 1/16 inch when there is no pressure on the boiler.