A. A boiler shall have a feed supply which permits it to be fed at any time while under pressure.
B. A boiler having more than 500 square feet of water-heating surface shall have at least two means of feeding, as follows:
(1) One means shall be an approved feed pump, injector, or inspirator;
(2) The other source may be directly from a water main, at a pressure 6 percent greater than the set pressure of the safety valve having the highest setting.
C. A boiler conforming to the ASME Code, PG-61.1, and fired by gaseous, liquid, or solid fuel in suspension may have a single feed supply provided that means are furnished for the immediate shutoff of heat input if the water feed is interrupted.
D. Feedwater shall be fed into a boiler so that it will not be introduced:
(1) Near a riveted joint of a shell or furnace sheet; or
(2) Directly against a surface exposed to:
(a) A product of combustion, or
(b) Direct radiation from the fire.
E. Feed Pipe.
(1) Feed pipe shall have a:
(a) Check valve near the boiler; and
(b) Valve or cock between the check valve and the boiler.
(2) When two or more boilers are fed from a common source, the branch to each boiler shall have a valve between the check valve and source of supply.
(3) The inlet of a globe valve on a feed pipe shall be under the disc of the valve.
(1) When a return is fed back to a boiler by gravity, each return line shall have, as close as practicable to the boiler, a:
(a) Check valve; and
(b) Stop valve placed between the boiler and the check valve.
(2) It is recommended that no stop valve be placed in the supply and return pipe connection of a single boiler installation.
G. Deaerating Heater. When a deaerating heater is:
(1) Not used, the recommended minimum temperature for feedwater is 120°F to avoid creating localized stress.
(2) Used, the recommended minimum feedwater temperature is 215°F, so that dissolved gases can be released completely.