1. (1) A blowoff as required herein is defined as a pipe connection provided with valves through which the water in the boiler may be blown out under pressure, excepting drains such as are used on water columns, gage glasses, or piping to feedwater regulators, etc., used for the purpose of determining the operating condition of such equipment. Piping connections used primarily for continuous operation, such as deconcentrators on continuous blowdown systems, are not classed as blowoffs but the pipe connections and all fittings up to and including the first shutoff valve shall be equal at least to the pressure requirements for the lowest set pressure of any safety valve on the boiler drum and with the corresponding saturated steam temperature.

2. (2) A surface blowoff shall not exceed 2½ inch pipe size, and the internal and external pipes, when used, shall form a continuous passage, but with clearance between their ends and arranged so that the removal of either will not disturb the other. A properly designed steel bushing, similar to or the equivalent of those shown in Figure P-42, or a flanged connection shall be used.

   ​

3. (3) Blowoff piping shall conform to the requirements of ASME, except that galvanized wrought iron or steel, brass or copper pipe shall not be used.

   (b)

4. (1) Each boiler except forced-flow steam generators with no fixed steam 2nd water line and high-temperature water boilers shall have a bottom blowoff outlet in direct connection with the lowest water space practicable for external piping conforming to ASME.
5. (2) Except as permitted for miniature boilers, the minimum size of pipe and fittings shall be one inch, and the maximum size shall be 2½ inches, except that for boilers with 100 square feet of heating surface or less, the minimum size of pipe and fittings may be ¾inch.
6. (3) Straight-run globe valves of the ordinary type as shown in Figure P-43(a), or valves of such type that dams or pockets can exist for the collection of sediment, shall not be used on such connections.
7. (4) Straightway “Y” type globe valves as shown in Figure P-43(b), or angle valves, may be used in vertical pipes, or they may be used in horizontal runs of piping provided they are so constructed or installed that the lowest edge of the opening through the seat shall be at least 25 percent of the inside diameter below the center line of the valve.
8. (5) Condensate return connections of the same size or larger than the size herein specified may be used, and the blowoff may be connected to them. In such case the blowoff must not be so located that the connection may be completely drained.

9. (6) All integral economizers, water walls, or water screens forming parts of a steam boiler shall be equipped with drain or blowoff valves conforming to the requirements of this subdivision and subdivisions (a) and (b) of section 14-9.29 of this Subpart for boilers.

   ​

(a)