# Title 33.1 — Department of Environmental Quality

## Article 33.1-14 — North Dakota Boiler Rules

## Chapter 33.1-14-05 — Power Boilers Power Boilers - Existing Installations

### § 33.1-14-05-01. Maximum allowable working pressure for standard boilers.

The maximum allowable working pressure for standard boilers must be determined in accordance
with the applicable provisions of the edition of the American Society of Mechanical Engineers Code
under which they were constructed and stamped.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-05-02. Maximum allowable working pressure for nonstandard boilers.

1. The maximum allowable working pressure on the shell of a nonstandard boiler must be
determined by the strength of the weakest section of the structure, computed from the
thickness of the plate, the tensile strength of the plate, the efficiency of the longitudinal joint or
tube ligaments, the inside diameter of the weakest course and the factor of safety allowed by
this article.
TStE = Maximum allowable working pressure, per square inch gauge where:
TS = Ultimate tensile strength of shell plates per square inch
t = Minimum thickness of shell plate, in weakest course, inches
E = Efficiency of longitudinal joint:
For tube ligaments and riveted construction, E shall be determined by the rules

given in section I, part PR, of the American Society of Mechanical Engineers
Code for power boilers. For seamless construction, E shall be considered one
hundred percent.
R = Inside radius of the weakest course of the shell, in inches
FS = Factor of safety permitted
2. When the tensile strength of steel or wrought iron shell plate is not known, it must be taken as
fifty-five thousand pounds per square inch [386.11 megapascals] for steel and forty-five
thousand pounds per square inch [310.26 megapascals] for wrought iron.
3. The resistance to crushing of mild steel must be taken at ninety-five thousand pounds per
square inch [655 megapascals] of the cross-sectional area.
4. When computing the ultimate strength of rivets in shear, the following values, in pounds per
square inch [megapascals] of the cross-sectional area of the rivet shank must be used:
Iron rivets in single shear 38,000 262.00
Iron rivets in double shear 76,000 524.00
Steel rivets in single shear 44,000 303.37
Steel rivets in double shear 88,000 606.69
When the diameter of the rivet holes in the longitudinal joints of a boiler is not known, the
diameter and cross-sectional area of rivets, after driving, may be selected from the following
table, or as ascertained by cutting out one rivet in the body of the joint.
Thickness of plate, inches 1/4 9/32 5/16 11/32 3/8 13/32
Diameter of rivet after driving, 11/16 11/16 3/4 3/4 13/16 13/16
inches
Thickness of plate, inches 7/16 15/32 1/2 9/16 5/8
Diameter of rivet after driving, 15/16 15/16 15/16 1-1/16 1-1/16
inches
5. The following factors of safety must be increased by the inspector if the condition and safety
of the boiler demand it:
a. The lowest factor of safety permissible on existing installations is four, except for
horizontal-return-tubular boilers having continuous longitudinal lap seams more than
twelve feet [3.66 meters] in length, when the factor of safety is eight; when this latter type
boiler is removed from its existing setting, it may not be reinstalled for pressures in
excess of fifteen pounds per square inch gauge [103 kilopascals].
b. Reinstalled or secondhand boilers must have a minimum factor of safety of six when the
longitudinal seams are of lap-riveted construction, and a minimum factor of safety of five
when the longitudinal seams are of butt-and-double-strap construction. Steam traction
engines must be considered as secondhand boilers for purposes of determining their
factors of safety.

History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-05-03. Age limit of existing boilers.

1. The age limit of any boiler of nonstandard construction is thirty years except that after a
thorough internal and external inspection and a hydrostatic pressure test of one and one-half
times the allowable working pressure held for a period of at least thirty minutes during which
no distress or leakage develops, any boiler having other than a lap-riveted longitudinal joint
may be continued in operation without reduction in working pressure. The age limit of any
boiler having lap-riveted longitudinal joints and operating at a pressure in excess of fifty
pounds per square inch [344.74 kilopascals] is twenty years; this type of boiler, when removed
from an existing setting, may not be reinstalled for a pressure in excess of fifteen pounds per
square inch [103 kilopascals]. A reasonable time for replacement, not to exceed one year, may
be given at the discretion of the chief boiler inspector.
2. The shell or drum of a boiler in which a typical lap seam crack is discovered along a
longitudinal riveted joint for either butt seam or lap joints must be permanently discontinued for
use under steam pressure. "Lap seam crack" means the typical crack frequently found in lap
seams extending parallel to the longitudinal joint and located either between or adjacent to
rivet holes.
3. The age limit of boilers of standard construction installed prior to the date this law becomes
effective is dependent on thorough internal and external inspection and hydrostatic pressure
test of one and one-half times the allowable working pressure for a period of thirty minutes. If
the boiler under these test conditions exhibits no distress or leakage, it may be continued in
operation at the same working pressure.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-05-04. Welded boilers.

Boilers that have either longitudinal or circumferential seams of fusion welded construction must
have been constructed and stamped in accordance with the rules and regulations of the American
Society of Mechanical Engineers Code or must have the standard stamping of another state that has
adopted a standard of construction equivalent to the standards of the American Society of Mechanical
Engineers Code.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-05-05. Pressure on old boilers.

The maximum working pressure of an old boiler may not be increased to a greater pressure than
would be allowed for a new boiler of the same construction.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07

### § 33.1-14-05-06. Cast iron headers and mud drums.

The maximum allowable working pressure on a watertube boiler, the tubes of which are secured to
a cast iron or malleable iron header, or which have cast iron mud drums, may not exceed one hundred
sixty pounds per square inch gauge [1103.17 kilopascals].
History: Effective July 1, 2020
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-05-07. Pressure on cast iron boilers.

The maximum allowable working pressure for any cast iron boiler, except hot water boilers, is
fifteen pounds per square inch gauge [103 kilopascals].
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-05-08. Safety valves and safety relief valves.

Safety valves and safety relief valves must meet the requirements of the edition of the American
Society of Mechanical Engineers Code, section 1, referenced in this article or the requirements of the
edition of the American Society of Mechanical Engineers Code, section 1, to which the boiler they are
installed was constructed.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-05-09. Superheater safety valve requirements.

Superheater safety valves must meet the requirements of the edition of the American Society of
Mechanical Engineers Code section referenced in this article or the requirements of the edition of the
American Society of Mechanical Engineers Code section to which the superheater they are installed
was constructed.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-05-10. Capacity.

1. The minimum safety valve or safety relief valve relieving capacity for all high-pressure boilers
other than steam traction engines must be determined by the edition of the American Society
of Mechanical Engineers Code, section 1, referenced in this article or by the requirements of
the American Society of Mechanical Engineers Code, section 1, to which the boiler they are
installed was constructed.
2. The minimum safety valve relieving capacity for steam traction engines must be determined
using the edition of the National Board Inspection Code referenced in this article.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07

### § 33.1-14-05-11. Mounting.

The mounting of safety valves and safety relief valves must meet the requirements of the edition of
the American Society of Mechanical Engineers Code, section 1, referenced in this article or by the
requirements of the edition of the American Society of Mechanical Engineers Code, section 1, to which
the boiler they are installed was constructed.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-05-12. Operation.

1. The operation of safety valves and safety relief valves must meet the requirements of the
edition of the American Society of Mechanical Engineers Code, section 1, referenced in this
article or by the requirements of the edition of the American Society of Mechanical Engineers
Code, section 1, to which the boiler they are installed was constructed.
2. If the operating conditions of a valve are changed so as to require a new spring for a different
pressure, the valve must be adjusted by the manufacturer, the manufacturer's authorized
representative, or by a holder of a valid national board "VR" certificate who shall furnish and
install a new nameplate.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-05-13. Steam stop valves.

1. Each discharge outlet, except safety valve, safety relief valves, reheater inlet and outlet, or
superheater inlet connections, must be fitted with a stop valve located at an accessible point
in the steam-delivery line and as near the boiler nozzle as is convenient and practicable.
When such outlets are over two inch [50.8 millimeter] pipe size, the valve or valves used on
the connection must be of the outside-screw-and-yoke-rising-spindle type so as to indicate
from a distance by the position of its spindle whether it is closed or open, and the wheel may
be carried either on the yoke or attached to the spindle. A plug-cock-type valve may be used
provided the plug is held in place by a guard or a gland, the valve is equipped to indicate from
a distance whether it is closed or open, and the valve is equipped with a slow-opening
mechanism. In the case of a single boiler and prime mover installation, the stop valve required
herein may be omitted provided the prime mover throttle valve is equipped with an indicator to
show whether the valve is open or closed and is designed to withstand the required
hydrostatic pressure test of the boiler.
2. When the boilers are connected to a common header, the connection from each boiler having
a manhole opening must be fitted with two stop valves having an ample free-blow drain
between them. The discharge of this drain must be visible to the operator while manipulating
the valve. The stop valves must consist preferably of one automatic nonreturn valve (set next
to the boiler) and a second valve of the outside-screw-and-yoke type must be used. Where
intercommunicating systems of different pressures are installed, every boiler on each system
must be equipped with an automatic nonreturn valve set next to the boiler.
3. When more than one stop valve is required, it must have a pressure rating at least equal to
that required for the expected steam temperature and pressure at the valve, or the pressure
rating at least equal to eighty-five percent of the lowest set pressure of any safety valve on the
boiler drum and for the expected temperature of the steam at the valve, whichever is greater.

4. All valves and fittings on steam lines must have a pressure rating of at least one hundred
pounds per square inch [689.48 kilopascals] in accordance with the applicable American
National Standards Institute Standard.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-05-14. Feedwater valves and piping.

1. Except for high-temperature water boilers, the feed piping must be provided with a check
valve near the boiler and a valve or cock between the check valve and the boiler. When two or
more boilers are fed from a common source, there also must be a globe or regulating valve on
the branch to each boiler located between the check valve and the source of supply.
Whenever globe valves are used on feed piping, the inlet must be under the disk of the valve.
On single boiler-turbine unit installations, the boiler feed shutoff valve may be located
upstream from the boiler feed check valve.
2. When the supply line to a boiler is divided into branch feed connections and all such
connections are equipped with stop-and-check valves, the stop-and-check valves in the
common source may be omitted.
3. If a boiler is equipped with duplicate feed arrangements, each such arrangement must be
equipped as required by these rules.
4. A combination stop-and-check valve in which there is only one seat and disk and a valve stem
is provided to close the valve when the stem is screwed down must be considered only as a
stop valve, and a check valve must be installed as otherwise provided.
5. Where an economizer or other feedwater-heating device is connected directly to the boiler
without intervening valves, the feed valves and check valves required must be placed on the
inlet of the economizer or feedwater-heating device.
6. The recirculating return line for a high-temperature water boiler must be provided with the
same stop valve, or valves, required by subsection 1 of section 33.1-14-05-13 for the main
boiler and the required stop valve or valves is optional. A check valve may not be a substitute
for a stop valve.
7. Except as provided for in subsections 8 and 10, boilers having more than five hundred square
feet [46.45 square meters] of water-heating surface must have at least two means of feeding
water. Each source of feeding must be capable of supplying water to the boiler at a pressure
of six percent higher than the highest setting of any safety valve on the boiler. For boilers that
are fired with solid fuel not in suspension, and for boilers whose setting or heat source can
continue to supply sufficient heat to cause damage to the boiler if the feed supply is
interrupted, one such means of feeding must not be subject to the same interruption as the
first method.
8. Except as provided for in subsection 7, boilers fired by gaseous, liquid, or solid fuel in
suspension may be equipped with a single means of feeding water provided means are
furnished for the immediate shut off of heat input if the water feed is interrupted.
9. For boilers having a water-heating surface of not more than one hundred square feet [9.29
square meters], the feed piping and connection to the boiler may not be smaller than one-half
inch [12.7 millimeter] pipe size. For boilers having a water-heating surface more than one
hundred square feet [9.29 square meters], the feed piping and connection to the boiler may
not be less than three-quarter inch [19.05 millimeter] pipe size.

10. High-temperature water boilers must be provided with means of adding water to the boiler or
system while under pressure.
11. The feedwater must be introduced into a boiler in such a manner that the water will not be
discharged directly against surfaces exposed to gases of high temperature or to direct
radiation from the fire or close to any riveted joints of the furnace sheets or of the shell. For
pressures of four hundred pounds [2757.92 kilopascals] or over, the feedwater inlet through
the drum must be fitted with shields, sleeves, or other suitable means to reduce the effects of
temperature differentials in the shell or head. If necessary, the discharge end of the feed
piping must be fitted with a baffle to divert the flow from riveted joints. Feedwater may not be
introduced through the blowoff.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-05-15. Blowoff valves and piping.

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].
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-05-16. Factors of safety.

The minimum factor of safety may not be less than four for existing installations. The director
authorizes an inspector to increase the factor of safety if the condition of the boiler or pressure vessel
warrants it. If the owner or user does not concur with the inspector's decision, the owner or user may
appeal to the director who may request a joint inspection by the chief boiler inspector and the deputy
inspector or special inspector. Each inspector shall render the inspector's report to the director, and the
director shall render the final decision, based upon the data contained in all the inspector's reports.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-05-17. Inspection of inaccessible parts.

If in the opinion of the inspector, as the result of conditions disclosed at the time of inspection, it is
advisable to remove the interior or exterior lining, covering, or brickwork to expose certain parts of the
vessel not normally visible, the owner or user shall remove such material to permit proper inspection
and the drilling of any part of the vessel to ascertain thickness.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-05-18. Repairs and renewals of fittings and appliances.

Whenever repairs are made to fittings and appliances or it becomes necessary to replace them, the
work must comply with the requirements for new installations.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-05-19. Fusible plugs.

1. Fire-actuated fusible plugs, if used, must conform to the requirements of the American Society
of Mechanical Engineers Code for power boilers.

2. They may be replaced by steel plugs if the boiler is gas-fired or oil-fired and is equipped with a
low water fuel cutoff.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-05-20. Water columns, gauge glasses, and gauge cocks.

1. Outlet connections (except for damper regulator, feedwater regulator, low-water fuel cutoff,
drains, steam gauges, or such apparatus that does not permit the escape of an appreciable
amount of steam or water therefrom) may not be placed on the piping that connects the water
column to the boiler. The water column must be placed on the piping that connects the water
column to the boiler. The water column must be provided with a valved drain of at least
three-quarter inch [19.05 millimeter] pipe size, the drain to be piped to a safe location.
2. Each boiler constructed prior to 1999 must have three or more gauge cocks located within the
visible length of the water glass, except when the boiler has two water glasses located on the
same horizontal lines. Boilers not over thirty-six inches [.914 meters] in diameter, in which the
heating surface does not exceed one hundred square feet [9.29 square meters] need have but
two gauge cocks.
3. For all installations where the water gauge glass or glasses are more than thirty feet
[9.14 meters] from the boiler operating floor, it is recommended that water level indicating or
recording gauges be installed at eye height from the operating floor.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-05-21. Steam pressure gauge.

1. Each steam boiler must have a steam gauge, with dial range not less than one and one-half
times the pressure at which the safety valve is set, connected to the steam space or to the
steam connection to the water column. The steam gauge must be connected to a siphon or
equivalent device of sufficient capacity to keep the gauge tube filled with water and so
arranged that the gauge cannot be shut off from the boiler except by a cock placed near the
gauge and provided with a tee or lever handle arranged to be parallel to the pipe in which it is
located when the cock is open.
2. When a steam pressure gauge connection longer than eight feet [2.44 meters] becomes
necessary, a shutoff valve may be used near the boiler provided the valve is of the
outside-screw-and-yoke type and is locked open. The line must be ample size with provision
for free blowing. Each boiler must be provided with a one-quarter inch [6.35 millimeter] nipple
and globe valve connected to the steam space for the exclusive purpose of attaching a test
gauge when the boiler is in service so that the accuracy of the boiler steam gauge may be
ascertained.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-05-22. Pressure on nonstandard steam traction engines.

All steam traction engines that are of nonstandard boiler construction are limited to a maximum
allowable working pressure of one hundred pounds per square inch [690 kilopascals], unless a
thorough ultrasonic thickness survey, engineering analysis, and other inspections, approved by the

chief boiler inspector, determine that a different pressure is appropriate. The maximum allowable
working pressure may not be greater than that permitted by the original manufacturer. Boilers herein
described are not subject to the age limits of section 33.1-14-05-03.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-05-23. Duties of owners.

1. It is the duty of the owner or user of any steam traction engine on wheels to notify the chief
boiler inspector of sale or other disposition of steam traction engines.
2. Within ten days of purchase, any person purchasing any steam traction engine shall notify the
chief boiler inspector where it will be located and operated.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-04
Law Implemented: NDCC 23.1-16-04
### § 33.1-14-05-24. Inspection and repair of standard and nonstandard steam traction engines.

The National Board Inspection Code referenced in this article must be used for the inspection and
repair of all steam traction engines unless otherwise noted in this article.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-05
Law Implemented: NDCC 23.1-16-05
