Section 408.4284. Relieving capacity required.

(1) The required steam-relieving capacity, in pounds per hour, of the pressure-relieving device or devices on a boiler shall be  the greater of that determined by dividing the maximum output in Btu  at   the boiler nozzle obtained by the firing of any fuel for which the unit is designed by 1,000 or by multiplying the square feet of heating surface by 5.

In many cases a greater relieving capacity  of  valves  will      have    to    be provided than the minimum specified by these rules.  In   every   case,    the requirements of subrule

(3)   shall be met.

(2)   When operating conditions are changed, or additional boiler heating surface is installed, the valve capacity shall be increased, if necessary, to meet the new conditions and be  in   accordance  with    subrule   (3).   The additional valves required, on  account of changed conditions, may be installed on the outlet piping provided there is an intervening valve.

(3)   Relief valve capacity for each boiler shall be such  that  with  the maximum heat input the pressure cannot rise more than 6 psi above the maximum allowable pressure for pressures up to and including 60 psi and 10% for maximum allowable working pressures over 60 psi.

History: 1979 AC.