Sec. 14-10.21. Bottom blowoff pipes

(a) Each boiler shall have a blowoff pipe fitted with a valve or cock, in direct connection with the lowest water space practicable.

(b) When the maximum allowable working pressure exceeds 100 pounds per square inch, the blowoff pipe shall be extra heavy from boiler to valve or valves, and shall run full size without reducers or bushings. All fittings between the boiler and valve shall be steel or extra heavy fittings of bronze, brass, malleable iron or cast iron. In case of replacement of pipe or fittings in the blowoff lines, as specified in this subdivision, they shall be installed in accordance with the rules for new installations. (See sections 14-9.27—14-9.29 of this Part.)

(c) When the maximum allowable working pressure exceeds 100 pounds per square inch, each bottom blowoff pipe shall be fitted with an extra-heavy valve or cock. Preferably two valves, or a valve and a cock should be used on each blowoff, in which case such valves, or a valve and a cock, shall be extra heavy.

(d) A bottom blowoff pipe when exposed to direct furnace heat, shall be protected from the products of combustion by firebrick, a substantial cast-iron removable sleeve, or a covering of nonconducting material.

(e) An opening in the boiler setting for a blowoff pipe shall be arranged to provide for free expansion and contraction.