North Dakota Administrative Code › Title 33.1 - Department of Environmental Quality › Article 33.1-14 - NORTH DAKOTA BOILER RULES › Chapter 33.1-14-05 - POWER BOILERS - EXISTING INSTALLATIONS › Section 33.1-14-05-15 - Blowoff valves and piping

Current through Supplement No. 393, July, 2024
1. A
				"blowoff" means 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, gauge glasses, or piping of 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 must 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. A
				surface blowoff may not exceed two and one-half inch [63.5 millimeter] pipe
				size, and the internal and external pipes, when used, must form a continuous
				passage, but with clearance between their ends and arranged so that the removal
				of either will not disturb the other.
3. Each boiler, except high temperature water
				boilers, must have a bottom blowoff pipe fitted with a valve or cock in direct
				connection with the lowest water space practicable.
4. All waterwalls and water screens which do
				not drain back into the boiler, and all integral economizers must be equipped
				with blowoff valves.
5. Except as
				permitted for miniature boilers, the minimum size of pipe and fittings is one
				inch [25.4 millimeters], and the maximum size is two and one-half inches [63.5
				millimeters], except that for boilers with one hundred square feet [9.29 square
				meters] of heating surface or less, the minimum size of pipe and fittings is
				three-fourths inch [19.05 millimeters].
6. 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 be so located that the
				connection may be completely drained.
7. A bottom blowoff pipe when exposed to
				direct furnace heat must be protected by firebrick or other heat-resisting
				material which is so arranged that the pipe may be inspected.
8. An opening in the boiler setting for a
				blowoff pipe must be arranged to provide free expansion and
				contraction.
9. On a boiler having
				multiple blowoff pipes, a single master valve may be placed on the common
				blowoff pipe from the boiler, in which case only one valve on each individual
				blowoff is required. In such a case either the master valve or the individual
				valves or cocks must be of the slow-opening type.
10. Two independent slow-opening valves, or a
				slow-opening valve and a quick-opening valve or cock, may be combined in one
				body and may be used provided the combined fitting is the equivalent of two
				independent slow-opening valves, or a slow-opening valve and a quick-opening
				valve or cock and provided further that the failure of one to operate cannot
				affect the operation of the other.
11. The bottom blowoff pipes of every
				traction or portable boiler must have at least one slow-opening or
				quick-opening blowoff valve or cock conforming to the requirements of section
				33.1-14-05-15.
12. Only one blowoff
				valve, which must be of a slow-opening type, is required on forced circulation
				and electric boilers having a normal water content not exceeding one hundred
				gallons [378.54 liters].
General Authority:
NDCC 23.1-16
Law Implemented:
NDCC
					 23.1-16