815 KAR 15:040.
Power boiler and pressure vessel supplemental requirements.
RELATES TO: KRS
AND CONFORMITY: KRS 236.030 authorizes the executive director, through the
Board of Boiler Rules, to fix reasonable standards for the safe construction,
installation, inspection and repair of boilers and pressure piping. This administrative
regulation sets forth the specific requirements for power boilers which are
within the scope of Section I of the ASME Boiler and Pressure Vessel Code. This
amendment is necessary to comply with KRS Chapter 13A and to set forth
additional specific requirements for new and existing power boilers which do
not apply to other vessels.
Section 1. New
Installations. (1) Power boilers. All power boilers shall be constructed in
accordance with applicable provisions of the ASME Boiler and Pressure Vessel
Code incorporated in 815 KAR 15:025, Section 1(1), and Title 815 Chapter 15 of
the Kentucky administrative regulations. Pressure piping beyond the first (or
second) stop valve shall comply with the ASME Code for Pressure Piping adopted
by reference in 815 KAR 15:025, Section 1(3).
(a) Vessels subject
to external corrosion shall be so installed that there is sufficient access to
all parts of the exterior to permit proper inspection of the exterior surfaces,
otherwise sufficient protection against corrosion shall be provided, or the
vessel shall be of such size, dimension and connected that it can be readily removed
from its location for inspection.
(b) Vessels having
handholes, manholes, or cover plates to permit inspection of interior surfaces
shall be so installed that these openings are readily accessible.
(c) When cylindrical
vessels are installed in a vertical position and subject to corrosion, the
bottom head, if dished, should be concave to pressure to facilitate proper
(d) The installed
vessel shall be so located that the stamping or marking shall be accessible to
the inspector and shall not be obliterated by insulation or other covering not
relieving devices (pressure vessels):
(a) Single pressure
relieving devices shall be set to operate at a pressure not exceeding the
maximum allowable working pressure (MAWP) of the vessel.
(b) All pressure
vessels other than unfired steam boilers shall be protected by a pressure
relieving device that shall prevent the pressure within the vessel from rising
more than five (5) percent above the maximum allowable working pressure (MAWP)
when full open and discharging, except as in paragraphs (c) and (d) of this
subsection. Unfired steam boilers shall have protective devices as required by
this administrative regulation.
(c) The aggregate
capacity of the pressure relieving devices connected to any vessel or system of
vessels for the release of a liquid, air, steam, or other vapor shall be
sufficient to discharge the maximum quantity that can be generated or supplied
to the attached equipment without permitting a rise in pressure within the
vessel or more than sixteen (16) percent above the maximum allowable working
pressure (MAWP) of the vessel when all pressure relieving devices are full open
(d) Where an
additional hazard can be created by exposure of a pressure vessel to fire or
other unexpected sources of external heat, supplemental pressure relieving
devices shall be installed capable of protecting against excessive pressure.
These supplemental pressure relieving devices shall be capable of preventing the
pressure from rising more than twenty-one (21) percent above the maximum
allowable working pressure.
relieving devices shall be constructed, located, and installed so that they are
readily accessible for inspection and repair and so that they cannot be readily
rendered inoperative and shall be selected on the basis of their intended
(f) Safety, safety
relief, and relief valves shall be of the direct spring loaded type.
(g) Pilot operated
pressure relief valves may be used, provided that the pilot is self-actuated
and the main valve will open automatically at not over the set pressure and
will discharge its full rated capacity if some essential part of the pilot
(h) The spring in a
pressure relief valve in service for pressures up to and including 250 psi
shall not be reset for any pressure more than ten (10) percent above or below
that for which the valve is marked. For higher pressures, the spring shall not
be reset for any pressure more than five (5) percent above or five (5) percent
below that for which the safety or relief valve is marked.
(i) The set pressure
tolerances, plus or minus, of pressure relief valves shall not exceed two (2)
psi for pressures up to and including seventy (70) psi and three (3) percent for
pressures above seventy (70) psi. All other requirements regarding over
pressure protection devices shall be in accordance with UG 125 through UG 136
of ASME Pressure Vessel Code, Section VIII, Division 1.
Section 2. Maximum
Allowable Working Pressure for Existing Installations. (1) Maximum allowable
working pressure for standard boilers and pressure vessels. The maximum
allowable working pressure for standard boilers and pressure vessels shall be
determined in accordance with the applicable provision of the edition of ASME
Boiler and Pressure Vessel Code under which they were constructed and stamped.
allowable working pressure for nonstandard boilers.
(a) The maximum
allowable working pressure on the shell of a nonstandard boiler, pressure
vessel or drum shall 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
subsection (h) of this section.
(b) Formulas. (TS
times t times E) divided by (R times FS) equals maximum allowable working
pressure in psig; where,
1. TS = ultimate
tensile strength of shell plates psi.
2. t = minimum
thickness of shell plate, of weakest course, in inches.
3. E = efficiency of
(c) For riveted
construction, E may be determined under Paragraph PR-15 of ASME Boiler and
Pressure Vessel Code for Power Boilers.
(d) For tube
ligaments, E shall be determined by rules given in Paragraphs PG-52 and 53 of
ASME Boiler and Pressure Vessel Code for Power Boilers.
construction, E shall be considered 100 percent.
R = inside radius of
the weakest course of the shell or drum in inches.
FS = factor of
strength. When the tensile strength of steel or wrought iron shell plates is
not known, it shall be taken at 55,000 psi for steel and 45,000 psi for wrought
strength of mild steel. The resistance to crushing of mild steel shall be taken
at 95,000 psi of cross section area.
(g) Strength of
rivets in shear. When computing the ultimate strength of rivets in shear, the
following values in pounds psi of the cross sectional area of the rivet shank
shall be used:
Iron rivets in single
Iron rivets in double
Steel rivets in single
Steel rivets in double
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 (1) rivet in the
body of the joint:
OF RIVETS BASED ON PLATE THICKNESS
Thickness of plate
Diameter of rivet after
Thickness of plate
Diameter of rivet after
(h) Factors of
safety. The following factors of safety shall be increased by the inspector if
the condition and safety of the boiler demand it:
1. The lowest factor
of safety permissible on existing installations shall be four and five-tenths
(4.5) except for horizontal return tubular boilers having continuous
longitudinal lap seams more than twelve (12) feet in length where the factor of
safety shall be eight (8), but when the boiler is removed from its existing
setting, it shall not be reinstalled for pressure in excess of fifteen (15)
2. Reinstalled or
secondhand nonstandard boilers shall have a minimum factor of safety of six (6)
when the longitudinal seams are of lap riveted construction and minimum factor
of safety of five (5) when the longitudinal seams are of butt and double strap
(3) Age limit of
fire tube boilers. The age limit of a horizontal return tubular, flue or
cylinder boiler having a longitudinal lap joint and operating at a pressure in
excess of fifty (50) lbs. psig shall be twenty (20) years.
(4) Welded boilers.
Boilers having either longitudinal or circumferential seams of fusion welded
construction shall have been constructed and stamped in accordance with the
rules and regulations of the ASME Boiler and Pressure Vessel Code for Power
Boilers or shall have the standard stamping of a state that has adopted a
standard of construction equivalent to the standards of the ASME Code for Power
Boilers and Pressure Vessels.
(5) Cast iron
headers and mud drums. The maximum allowable working pressure on a water tube
boiler, the tubes of which are secured to cast iron or malleable iron headers,
or which have cast iron mud drums, shall not exceed 160 lbs. psig.
(6) Pressure on cast
iron boilers. The maximum allowable working pressure for any cast iron boiler,
except for hot water boilers, shall be fifteen (15) lbs. psig.
(7) Safety valve
requirements for power boilers:
(a) The use of
weight-level safety valves shall not be used and the valves shall be replaced
by safety valves that conform to the requirements of the ASME Code for Power
(b) Safety valves
having either the seat or disc of cast iron shall not be used.
(c) Each boiler
shall have at least one (1) safety valve, and, if it has more than 500 square
feet of water heating surface, it shall have two (2) or more safety valves.
(d) Safety valves
and safety relief valves shall be installed with their spindles vertical.
(e) The method of
computing the steam generating capacity of the boiler shall be as given in paragraph
A-12 of the ASME Boiler and Pressure Vessel Code for Power Boilers. The safety
valve or valves shall be connected to the boiler, independent of any other
steam connection, and attached to the boiler, without intervening pipe or
fittings. If alteration is required to conform to this requirement, owners and
users shall be allowed one (1) year in which to complete the work. Valves shall
not be placed between the safety valve and the boiler or on the discharge pipe
(if used) between the safety valve and the atmosphere. If a discharge pipe is
used, it shall be full sized and fitted with an open drain to prevent water
lodging in the upper part of the safety valve or discharge pipe and supported
independently of the safety valve. If an elbow is placed on a safety valve or
discharge pipe, it shall be located close to the safety valve outlet. All
safety valve discharges shall be located or piped to avoid endangering persons
using walkways or platforms used to control the main valves of boilers or steam
(f) The safety valve
capacity of each boiler shall be sufficient to allow the safety valve or valves
to discharge all the steam generated by the boiler without allowing the
pressure to rise more than six (6) percent above the maximum allowable working
(g) For each boiler,
one (1) or more safety valves on the boiler shall be set at or below the
maximum allowable working pressure. If additional valves are used, the highest
pressure setting shall not exceed the maximum allowable working pressure by
more than three (3) percent. The complete range of pressure settings of all of
the saturated steam safety valves on a boiler shall not exceed ten (10) percent
of the highest pressure to which any valve is set. If two (2) or more boilers
operating at different pressures and safety valve settings are interconnected,
the lower pressure boilers or interconnected piping shall be equipped with
safety valves of sufficient capacity to prevent overpressure considering the
generating capacity of all boilers. If the boiler is supplied with feed water
directly from pressure mains without the use of feeding apparatus (not to
include return taps), safety valve shall not be set at a pressure greater than
ninety-four (94) percent of the lowest pressure obtained in the supply main
feeding the boiler.
(h) The relieving
capacity of the safety valves on any boiler may be checked by one (1) of the
three (3) following methods; and, if found to be insufficient, additional
capacity shall be provided.
1. By making the
accumulation test, which consists of shutting off all other steam discharge
outlets from the boiler and forcing the fires to the maximum. The safety valve
capacity shall be sufficient to prevent a pressure in excess of six (6) percent
above the maximum allowable working pressure. This method shall not be used on
a boiler with a superheater or reheater.
2. By measuring the
maximum amount of fuel that can be burned and computing the corresponding
evaporative capacity (steam generating capacity) upon the basis of the heating
valve of this fuel. This computation may be made as outlined in the Appendix of
the ASME Code for Power Boilers.
3. By determining
the maximum evaporative capacity by measuring the feed water.
4. If either of the
methods outlined above is employed, the sum of the safety valve capacity shall
be equal to or greater than the maximum evaporative capacity (maximum steam
generating capacity) of the boiler. The minimum safety valve or safety relief
valve relieving capacity for other than electric boilers shall be determined on
the basis of the pounds of steam generated per hour per square foot of boiler
heating surface and water wall heating surface, as given in the following
POUNDS OF STEAM PER HOUR
SQUARE FOOT OF SURFACE
Boiler heating surface
Oil-, gas-, or pulverized-fuel-fired
Oil-, gas-, or pulverized-fuel-fired
a. If a boiler is
fired only by a gas having a heat value in excess of 200 BTU per cubic foot,
the minimum safety valve or safety relief valve relieving capacity may be based
on the values given for hand-fired boiler above.
b. The minimum
safety valve or safety relief valve relieving capacity for electric boilers
shall be three and one-half (3 1/2) pounds per hour per kilowatt input.
(8) Boiler feeding
and feed piping: Except as allowed by paragraphs (b) through (f) of this
subsection, boilers having more than 500 square feet of water-heating surface
shall have at least two (2) means of feeding water. Each source of feeding
shall be capable of supplying water to the boiler at a pressure of three (3)
percent higher than the highest setting of any safety valve on the boiler.
(a) All boilers
shall have a feed supply which allows the boiler to be fed at any time while
(b) 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 (1) such means of feeding shall be steam
(c) Boilers fired by
gas, liquid, or solid fuel in suspension, may be equipped with a single means
of feeding water if furnished for the immediate shut off of the heat input if
the water feed is interrupted. If the boiler has a water-heating surface of not
more than 100 square feet, the feed piping and connection to the boiler shall
not be smaller than one-half (1/2) inch pipe size. If the boiler has a
water-heating surface more than 100 square feet, the feed piping and connection
to the boiler shall not be less than three-fourths (3/4) inch pipe size.
(d) High temperature
water boilers shall be provided with means of adding water to the boiler or
system while under pressure. The feed water shall be introduced into the boiler
to prevent its discharge close to riveted joints of the shell, furnace sheets,
directly against surfaces exposed to gases at high temperature or direct
radiation from the fire.
(e) The feed pipe to
the boiler shall be provided with a check valve near the boiler and a valve or
cock between the check valve and the boiler. If two (2) or more boilers are fed
from a common source, there shall also be a globe or regulating valve on the
branch to each boiler between the check valve and source of supply. If globe
valves are used on feed piping, the inlet shall be under the disc of the valve.
The valve shall be located as close to the boiler as is practicable.
(f) If de-aerating
heaters are not employed, it is recommended that the temperature of the feed
water be no less than 120 degrees Fahrenheit to avoid the possibility of
setting up localized stress. If de-aerating heaters are employed, it is
recommended that the minimum feed water temperature be no less than 215 degrees
Fahrenheit so that dissolved gases may be thoroughly released.
(9) Fusible plugs.
Fire-actuated fusible plugs, if used, shall conform to the requirements of the
ASME Boiler and Pressure Vessel Code for Power Boilers, Sections A-19, A-20 and
(10) Water columns,
gauge glasses, and gauge cocks.
connections, except for damper regulator, feed water regulator, low-water fuel
cutout, drains, steam gauges, or apparatus that does not permit the escape of
an appreciable amount of steam or water shall not be placed on the piping that
connects the water column to the boiler. The minimum size of the steam and
water connection to the water column shall be one (1) inch pipe size, and each
water column shall be provided with a valved drain of at least three-fourths
(3/4) inch pipe size. The drain shall be piped to a safe location.
(b) Each boiler
shall have three (3) or more gauge cocks located within the range of the
visible length of the water glass, except when the boiler has two (2) water
glasses with independent connections to the boiler located on the same
horizontal lines and not less than two (2) feet apart. Two (2) gauge cocks are
sufficient for boilers not over thirty-six (36) inches in diameter in which the
heating surface does not exceed 100 square feet.
(c) Gauge cocks are
not required for electric boilers operating at pressures not exceeding 400 psi.
The gauge cock connections shall be not less than one-half (1/2) inch pipe
(d) For all
installations where the water gauge glass or glasses are more than thirty (30)
feet from the boiler operating floor, it is recommended that water level
indicating or recording gauges be installed at eye height from the operating
(11) Pressure gauges.
(a) Each boiler
shall have a pressure gauge connected to the steam space or to the water column
or its steam connection. The pressure gauge shall 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. The dial of the pressure gauge shall be graduated to approximately double
the pressure at which the safety valve is set, but, in no case to less than one
and one-half (1 1/2) times the pressure.
(b) If a pressure
gauge connection longer than eight (8) feet 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 or wired open. The line shall be ample size with provisions
for free blowing.
(c) Each boiler
shall be provided with a one-fourth (1/4) inch 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 pressure gauge may be
(12) Stop valves.
(a) Each outlet from
a boiler (except safety valve connections) shall be fitted with a stop valve
located as close as practicable to the boiler.
(b) If boilers
provided with manholes are connected to a common main, the steam or high
temperature water connection from each boiler shall be fitted with two (2) stop
valves having an ample free blow drain between them. The discharge of this
drain shall be visible to the operator while manipulating the valves and shall
be piped clear of the boiler setting. The stop valves shall consist of one (1)
automatic nonreturn valve (set next to the boiler) and a second valve of the
outside screw and yoke type shall be installed in accordance with Section I of
the ASME Boiler and Pressure Vessel Code.
(a) The construction
of the setting around each blow-off pipe shall permit free expansion and
contraction. Careful attention shall be given to the problem of sealing these
setting openings without restricting the movement of the blow-off piping. All
blow-off piping, when exposed to furnace heat, shall be protected by firebrick
or other heat resisting material constructed to allow close inspection of the
(b) When the maximum
allowable working pressure exceeds 100 psig, blow-off piping shall be extra
heavy from the boiler to the valve or valves, and shall be run full size
without use of reducers or bushings. The piping shall be of extra heavy wrought
iron or steel and shall not be galvanized. All fittings between the boiler and
blow-off valve shall be steel or extra heavy fittings of malleable iron. In
case of renewal of blow-off pipe or fittings, they shall be installed in
accordance with rules and administrative regulations for new installations.
(a) Ordinary type
straight-run globe valves in which dams or pockets may exist for the collection
of sediment shall not be used on these connections. Straightway Y-type globe
valves 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
allowing the lowest edge of the opening through the seat to be at least
twenty-five (25) percent of the inside diameter below the center line of the
(b) The blow-off
valve or valves and the pipe between them and the boiler shall be of the same
size except where a larger pipe for the return of condensation is used as
provided for by the ASME Boiler and Pressure Vessel Code for Power Boilers. On
all boilers, except those used for high temperature water, traction or portable
purposes, when the allowable working pressure exceeds 100 psi, each bottom
blow-off pipe shall have two (2) slow-opening valves, or one (1) slow-opening
valve and a quick-opening valve, or a cock complying with the requirements of
the ASME Boiler and Pressure Vessel Code for Power Boilers.
(c) If a blow-off
cock is used, the plug shall be held in place by a guard or gland. The plug
shall be distinctly marked in line with the passage. A slow-opening valve
requires at least five (5) 360-degree turns of the operating mechanism to
change from full-closed to full-opening, or vice versa.
(d) If a boiler has
multiple blow-off pipes, a single master valve may be placed on the common
blow-off pipe from the boiler, in which case only one (1) valve on each
individual blow-off shall be required. In this case, either the master valve or
the individual valves or cocks shall be of the slow-opening type, or a
slow-opening valve and a quick-opening valve or cock may be combined in one (1)
body and may be used if the combined fitting is the equivalent of two (2)
independent slow-opening valves or a slow-opening valve and a quick-opening
valve or cock and if the failure of one (1) to operate cannot affect the
operation of the other. The bottom blow-off pipes of every traction engine or
portable boiler shall have at least one (1) slow-opening or quick-opening
blow-off valve or cock conforming to the requirements of Section I of the ASME
Boiler and Pressure Vessel Code. Only one (1) blow-off valve, which shall be of
a slow- opening type, shall be required on forced circulation and electric
boilers having a normal water content not exceeding 100 gallons.
(15) Boiler blowoff
equipment. The blowdown from a boiler or boilers that enters a sanitary sewer
system or blowdown which is considered a hazard to life or property shall pass
through some form of blowoff equipment that will reduce pressure and
temperature as required hereinafter.
(a) The temperature
of the water leaving the blowoff equipment shall not exceed 150 degrees
(b) The pressure of
the blowdown leaving any type of blowoff equipment shall not exceed five (5)
(c) The blowoff
piping and fittings between the boiler or boilers and the blowoff tank(s) shall
comply with Paragraphs PG-58 and PG-59 of the ASME Boiler and Pressure Vessel
Code, Section I.
(d) The blowoff tank
construction shall comply with ASME Pressure Vessel Code, Section VIII
(e) All materials
used in the fabrication of boiler blowoff equipment shall comply with Material
Section II of the ASME Boiler and Pressure Vessel Code.
(f) When a steam
separator is used, it shall be designed to withstand at least twice the
operating pressure of the separator and it shall be equipped with a vent,
inlet, outlet and a pressure gauge.
(g) All blowoff
equipment shall be fitted with openings to facilitate cleaning and inspection.
(h) A copy of a
booklet for the design, construction and arrangement of boiler blowoff
equipment may be obtained from the National Board of Boiler and Pressure Vessel
Inspectors, whose address is 1055 Crupper Avenue, Columbus, Ohio 43229.
(a) Piping connected
to the outlet of a boiler, which comes with the ASME Boiler and Pressure Vessel
Code requirements, shall be attached as follows:
1. Screwing into a
tapped opening with a screwed fitting or a valve at the other end.
2. Screwing each end
into tapered flanges, fittings, or valves with or without rolling or peening.
3. Bolted joints,
including those of the Van Stone type.
4. Expanding into
grooved holes, seal welding, if desired. Pipe which is expanded, rolled, or
peened shall be made from open-hearth or electric-furnace steel.
(b) If exposed to
products of combustion, blow-off piping of fire-tube boilers shall be attached
as outlined in paragraph 1 of subsection (a) of this section. If not so exposed
to products of combustion, the piping shall be attached as outlined in
paragraph (a)1, 2 or 3 of this subsection. Fusion welding for sealing purposes
at the junction of bolted joints may be used.
(c) Welding may be
used to attach piping to nozzles or fittings if the rules for fusion welding or
forge welding are followed. If two (2) or more boilers with manholes are
connected to a common steam or high temperature water main or header, all
welded external piping from the boiler out to the second stop valve shall be
installed by a manufacturer or contractor authorized to use any one (1) of the
American Society of Mechanical Engineers Code symbol stamps for pressure
piping, power boilers or assembly stamps. The piping or fittings, adjacent to
the welded joint farthest from the boiler, shall be stamped with the pressure
piping, power boiler or assembly code symbol stamp of the American Society of Mechanical
Engineers when approved by the inspector. (Recodified from 806 KAR 50:165,
7-5-78; Am. 16 Ky.R. 67; eff. 8-22-89; 20 Ky.R. 2731; 2981; eff. 5-18-94; TAm