Section 408.4223. Determining safety valve capacity.

(1) The relieving capacity of the safety valves on any boiler shall be checked by 1 of the following methods and, if found to be insufficient, additional valves shall be provided:

(a)       By making the accumulation test, which consists of shutting off all other steam discharge outlets from the boiler and forcing the fires to the maximum. The safety valve capacity shall be sufficient to prevent a rise of pressure in excess of 6% of the maximum allowable working pressure. This method should not be used on a boiler with a superheater or reheater.

(b)      By measuring the maximum amount of fuel that can be burned and computing the corresponding evaporative capacity (steam generating capacity) upon the basis of the heating value of this fuel. These computations shall be made as outlined in the appendix of the ASME power boiler code.

(c)     By measuring the maximum amount of feedwater that can be evaporated.

(2)      When either of the methods outlined in subrule (1) (b) or (c) is employed, the sum of the safety valve capacities shall be equal to or greater than the maximum evaporative capacity (maximum steam generating capacity) of the boiler.

History: 1979 AC; 2013 AACS.