Current through Register Vol. 48, No. 3, March 22, 2024
A. EBO-1 Age
Limit of Existing Boilers
1. The age limit of
any boiler of nonstandard construction, installed prior to the date the Act
became effective, shall be 30 years, except that a boiler having other than a
lap-riveted longitudinal joint, after a thorough internal and external
inspection and, when required by the inspector, a pressure test of 1-1/2 times
the allowable working pressure held for a period of at least 30 minutes during
which no distress or leakage develops, may be continued in operation at the
working pressure determined by EB0-3. The age limit of any nonstandard boiler
having lap-riveted longitudinal joints and operating at a pressure in excess of
50 psig shall be 20 years. This type of boiler, when removed from an existing
setting, shall not be reinstalled for a pressure in excess of 15 psig. A
reasonable time for replacement, not to exceed one year, may be given at the
discretion of the Board.
2. The age
limit of boilers of standard construction installed prior to the date this law
became effective shall be dependent on thorough internal and external
inspection and, where required by the inspector, a pressure test not exceeding
1-1/2 times the allowable working pressure. If the boiler, under these test
conditions, exhibits no distress or leakage, it may be continued in operation
at the working pressure determined by EB0-2.
3. The shell or drum of a boiler in which a
lap seam crack develops along a longitudinal lap riveted joint shall be
condemned. A lap seam crack is a crack found in lap seams extending parallel to
the longitudinal joint and located either between or adjacent to rivet
holes.
B. EB0-2 Maximum
Allowable Working Pressure for Standard Boilers
The maximum allowable working pressure for standard boilers
shall be determined in accordance with the applicable provisions of the edition
of the ASME Code under which they were constructed and stamped.
C. EB0-3 Maximum Allowable Working
Pressure for Nonstandard Boilers
1. The
maximum allowable working pressure for boilers fabricated by riveting shall be
determined by the applicable rules of the 1971 Edition of Section I of the ASME
Code. The lowest factor of safety permissible on existing installations shall
be 5.0, except for horizontal-return-tubular boilers having continuous
longitudinal lap seams more than 12 ft. in length, where the factor of safety
shall be 8. When this latter type of boiler is removed from its existing
setting, it shall not be reinstalled for pressures in excess of 15
psig.
2. The maximum allowable
working pressure for boilers of welded construction in service may not exceed
that allowable in Section I of the ASME Code for new boilers of the same
construction. The maximum allowable working pressure on the shell of a boiler
or drum shall be determined by the strength of the weakest course computed from
the thickness of the plate, the tensile strength of the plate, the efficiency
of the longitudinal joint, the inside diameter of the course, and the factor of
safety allowed by these rules in accordance with the following formula:
(TS)(t)(E)(R)(FS) = maximum allowable working pressure, psig
where:
(TS) = specified minimum tensile strength of shell plate
material, psi. When the tensile strength of steel or wrought-iron shell plate
is not known, it shall be taken as 55,000 psi for steel and 45,000 psi for
wrought iron
(t) = minimum thickness of shell plate, in weakest course,
inches
(E) = efficiency of longitudinal joint, method of determining
which is given in Paragraph PG-27 of Section I of the ASME Code
(R) = inside radius of the weakest course of the shell or
drum, inches
(FS) = factor of safety, which shall be at least 5.0
3. The inspector may increase the
factor of safety, if the condition and safety of the boiler warrant it.
D. EB0-4 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 psig.
E. EB0-5 Pressure on Cast-Iron Boilers
The maximum allowable working pressure for any cast-iron
boiler, except hot water boilers, shall be 15 psig. See EHB-1, 2, and 4.
F. EB0-6 Safety Valves
1. The use of weighted-lever safety valves or
safety valves having either the seat or disk of cast-iron are prohibited;
valves of this type of construction shall be replaced by direct, spring loaded,
pop-type valves that conform to the requirements of ASME Code, Section
1.
2. Each boiler shall have at
least one ASME/NB stamped and certified safety valve, and if it is a high
pressure boiler with a high pressure more than 500 sq. ft. of water-heating
surface, or an electric power input of more than 1,100 KW, it shall have two or
more safety valves of the same type.
3. The valve or valves shall be connected to
the boiler, independent of any other steam connection and attached as close as
possible to the boiler without unnecessary intervening pipe or fittings. Where
alteration is required to conform to this requirement, owners or users shall be
allowed reasonable time in which to complete the work as permitted by the chief
boiler administrator.
4. No valves
of any description shall be placed between the safety valve and the boiler or
on the escape pipe, if used. When an escape pipe is used, it shall be at least
the full size of the safety valve discharge and fitted with an open drain to
prevent water lodging in the upper part of the safety valve or in the escape
pipe. When an elbow is placed on a safety valve escape pipe, it shall be
located close to the safety valve outlet, or the escape pipe shall be anchored
and supported securely. All safety discharges shall be located and carried by a
pipe clear from walkways or platforms.
5. The safety valve capacity of each boiler
shall be such that the safety valve or valves will discharge all the steam that
can be generated by the boiler without allowing the pressure to rise more than
6 percent above the highest pressure to which any valve is set, and in no case
to more than 6 percent above the maximum allowable working pressure.
6. One or more safety valves on every boiler
shall be set at or below the maximum allowable working pressure. The remaining
valves may be set within a range of 3 percent above the maximum allowable
working pressure, but the range of setting of all the safety valves on a boiler
shall not exceed 10 percent of the highest pressure to which any valve is
set.
7. When boilers of different
maximum allowable working pressures with minimum safety valve settings varying
more than 6 percent are so connected that steam can flow toward the lower
pressure units, the latter shall be protected by additional safety valve
capacity, if necessary, on the lower pressure side of the system. The
additional safety valve capacity shall be based upon the maximum amount of
steam, which can flow into the lower pressure system.
8. In those cases where the boiler is
supplied with feed water directly from water mains without the use of feeding
apparatus (not to include return traps), no safety valve shall be set at a
pressure greater than 94 percent of the lowest pressure obtained in the supply
main feeding the boiler.
9. The
relieving capacity of the safety valves on any boiler shall be checked by one
of the following three methods and, if found to be insufficient, additional
valves shall be provided:
a. By making an
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 rise of pressure in excess of 6
percent of the maximum allowable working pressure. This method should not be
used on a boiler with a super heater or re-heater;
b. 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 value of this fuel.
These computations shall be made as outlined in the Appendix of the ASME Code,
Section l;
c. By measuring the
maximum amount of feed water that can be evaporated.
d. When either of the methods outlined in b
or c is employed, the sum of the safety valve capacities shall be equal to or
greater than the maximum evaporative capacity (maximum steam-generating
capacity) of the boiler.
G. EB0-7 Boiler Feeding
Each boiler shall have a feed supply, which will permit it to
be fed at any time while under pressure. A boiler having more than 500 sq. ft.
of water heating surface shall have at least two suitable means of feeding, at
least one of which shall be a feed pump. A source of feed at a pressure 6
percent greater than the set pressure of the safety valve with the highest
setting may be considered one of the means. Boilers fed by gaseous, liquid, or
solid fuel in suspension may be equipped with a single means of feeding water,
provided means are furnished for the shutoff of heat input prior to the water
level reaching the lowest safe level. The feed water shall 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 to direct radiation from the
fire. For pressures of 400 psig or over, the feed water inlet through the drum
shall be fitted with shields, sleeves, or other suitable means to reduce the
effects of temperature differentials in the shell or head. The feed piping 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. When two or more boilers are fed
from a common source, there shall also be a valve on the branch to each boiler
between the check valve and the source of supply. Whenever a globe valve is
used on feed piping, the inlet shall be under the disk of the valve. In all
cases where returns are fed back to the boiler by gravity, there shall be a
check valve and stop valve in each return line, the stop valve to be placed
between the boiler and the check valve, and both shall be located as close to
the boiler as is practicable. It is recommended that no stop valves be placed
in the supply and return pipe connections of a single boiler installation.
Where deaerating heaters are not employed, it is recommended that the
temperature of the feed water be not less than 120°F to avoid the
possibility of setting up localized stress. Where deaerating heaters are
employed, it is recommended that the minimum feed water temperature be not less
than 215°F so that dissolved gases may be thoroughly released.
H. EB0-8 Water Level Indicators
1. Each boiler, except forced-flow steam
generators with no fixed steam and waterline, and high temperature water
boilers of the forced circulation type that have no steam and waterline, shall
have at least one water gauge glass. Boilers operated at pressures over 400
psig shall be provided with two water gauge glasses which may be connected to a
single water column or connected directly to the drum.
2. Two independent remote level indicators
may be provided instead of one of the two required gauge glasses for boiler
drum water level indication in the case of power boilers with all drum safety
valves set at or above 900 psig. When both remote level indicators are in
reliable operation, the remaining gauge glass may be shut off, but shall be
maintained in serviceable condition.
3. When the direct reading of the gauge glass
water level is not readily visible to the operator in his/her working area, two
dependable indirect indications shall be provided, either by transmission of
the gauge glass image or by remote level indicators.
4. The lowest visible part of the water gauge
glass shall be at least 2 in. above the lowest permissible water level, at
which level there will be no danger of overheating any part of the boiler when
in operation at that level. When remote level indication is provided for the
operator in lieu of the gauge glass, the same minimum level reference shall be
clearly marked.
5. Connections from
the boiler to the remote level indicator shall be at least 3/4 in. pipe size to
and including the isolation valve and from there to the remote level indicator
at least 1/2 in. O.D. tubing. These connections shall be completely independent
of other connections for any function other than water level indication. For
pressures of 400 psig or over, lower connections to drums shall be provided
with shields, sleeves, or other suitable means to reduce temperature
differentials in the shells or heads.
6. Boilers of the horizontal fire tube type
shall be set so that when the water is at the lowest reading in the water gauge
glass, there shall be at least 3 in. of water over the highest point of the
tubes, flues, or crown sheets.
7.
Boilers of locomotives shall have at least one water glass provided with top
and bottom shutoff cocks and lamp, and two gauge cocks for boilers 36 in. in
diameter and under, and three gauge cocks for boilers over 36 in. in
diameter.
8. The lowest gauge cock
and the lowest reading of water glass shall not be less than 2 in. above the
highest point of crown sheet on boilers 36 in. in diameter and under, nor less
than 3 in. for boilers over 36 in. in diameter. These are minimum dimensions,
and on larger locomotives and those operating on steep grades, the height
should be increased, if necessary, to compensate for change of water level on
descending grades.
9. The bottom
mounting for water glass and for water column if used must extend not less than
1-1/2 in. inside the boiler and beyond any obstacle immediately above it, and
the passage therein must be straight and horizontal.
10. Tubular water glasses must be equipped
with a protecting shield.
11. All
connections on the gauge glass shall be not less than 1/2 in. pipe size. Each
water gauge glass shall be fitted with a drain cock or valve having an
unrestricted drain opening of not less than 1/4 in. diameter to facilitate
cleaning. When the boiler operating pressure exceeds 100 psig, the glass shall
be furnished with a connection to install a valved drain to the ash pit or
other safe discharge point.
12.
Each water gauge glass shall be equipped with a top and a bottom shutoff valve
of such through-flow construction as to prevent stoppage by deposits of
sediments. If the lowest valve is more than 7 ft. above the floor or platform
from which it is operated, the operating mechanism shall indicate by its
position whether the valve is open or closed. The pressure-temperature rating
shall be at least equal to that of the lowest set pressure of any safety valve
on the boiler drum and the corresponding saturated-steam temperature.
13. Straight-run globe valves shall not be
used on such connections.
14.
Automatic shutoff valves, if permitted to be used, shall conform to the
requirements of Section I of the ASME Code.
I. EBO-9 Water Columns
1. The water column shall be so mounted that
it will maintain its correct position relative to the normal waterline under
operating conditions.
2. The
minimum size of pipes connecting the water column to a boiler shall be 1 in.
For pressures of 400 psig or over, lower water column connections to drums
shall be provided with shields, sleeves, or other suitable means to reduce the
effect of temperature differentials in the shells or heads. Water glass
fittings or gauge cocks may be connected directly to the boiler.
3. The steam and water connections to a water
column or a water gauge glass shall be such that they are readily accessible
for internal inspection and cleaning. Some acceptable methods of meeting this
requirement are by providing a cross or fitting with a back outlet at each
right-angle turn to permit inspection and cleaning in both directions, or by
using pipe bends or fittings of a type which does not leave an internal
shoulder or pocket in the pipe connection and with a radius of curvature which
will permit the passage of a rotary cleaner. Screwed plug closures using
threaded connections as allowed by Section I of the ASME Code are acceptable
means of access for this inspection and cleaning. For boilers with all drum
safety valves set at or above 400 psig, socket-welded plugs may be used for
this purpose in lieu of screwed plugs. The water column shall be fitted with a
connection for a drain cock or drain valve to install a pipe of at least 3/4
in. pipe size to the ash pit or other safe point of discharge. If the water
connection to the water column has a rising bend or pocket, which cannot be
drained by means of the water column drain, an additional drain shall be placed
on this connection in order that it may be blown off to clear any sediment from
the pipe.
4. The design and
material of a water column shall comply with the requirements of Section I of
the ASME Code. Water columns made of cast iron in accordance with SA-278 may be
used for maximum boiler pressures not exceeding 250 psig. Water columns made of
ductile iron in accordance with SA-395 may be used for maximum boiler pressures
not exceeding 350 psig. For higher pressures, steel construction shall be
used.
5. Shutoff valves shall not
be used in the pipe connections between a boiler and a water column or between
a boiler and the shutoff valves required for the gauge glass, unless they are
either outside-screw-and-yoke or lever-lifting-type gate valves or stopcocks
with lever permanently fastened thereto and marked in line with their passage,
or of such other through-flow construction as to prevent stoppage by deposits
of sediment, and to indicate by the position of the operating mechanisms
whether they are in open or closed position; and such valves or cocks shall be
locked or sealed open. Where stopcocks are used, they shall be of a type with
the plug held in place by a guard or gland.
6. No outlet connections, except for control
devices (such as damper regulators and feed water regulators), drains, steam
gauges, or apparatus of such form as does not permit the escape of an
appreciable amount of steam or water there from, shall be placed on the pipes
connecting a water column or gauge glass to a boiler.
J. EB0-10 Gauge Glass Connections
Gauge glasses and gauge cocks that are not connected directly
to a shell or drum of the boiler shall be connected by one of the following
methods:
1. The water gauge glass or
glasses and gauge cocks shall be connected to an intervening water
column.
2. When only water gauge
glasses are used, they may be mounted away from the shell or drum and the water
column omitted, provided the following requirements are met.
a. The top and bottom gauge glass fittings
are aligned, supported, and secured so as to maintain the alignment of the
gauge glass;
b. The steam and water
connections are not less than 1 in. pipe size and each water glass is provided
with a valved drain; and
c. The
steam and water connections comply with the requirements of the following:
i. the lower edge of the steam connection to
a water column or gauge glass in the boiler shall not be below the highest
visible water level in the water gauge glass. There shall be no sag or offset
in the piping which will permit the accumulation of water; and
ii. the upper edge of the water connection to
a water column or gauge glass and the boiler shall not be above the lowest
visible water level in the gauge glass. No part of this pipe connection shall
be above the point of connection at the water column.
3. Each boiler (except those not
requiring water level indicators) shall 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.
4. Boilers not over 36 in. in diameter in
which the heating surface does not exceed 100 sq. ft. need have but two gauge
cocks.
5. The gauge cock
connections shall be not less than 1/2 in. pipe size.
K. EB0-11 Pressure Gauges
Each boiler shall have a pressure gauge so located that it is
easily readable. The pressure gauge shall be installed so that it shall at all
times indicate the pressure in the boiler. Each steam boiler shall have the
pressure gauge connected to the steam space or to the water column or its steam
connection. A valve or cock shall be placed in the gauge connection adjacent to
the gauge. An additional valve or cock may be located near the boiler,
providing it is locked or sealed in the open position. No other shutoff valves
shall be located between the gauge and the boiler. The pipe connection shall be
of ample size and arranged so that it may be cleared by blowing out. For a
steam boiler, the gauge or connection shall contain a siphon or equivalent
device, which will develop and maintain a water seal that will prevent steam
from entering the gauge tube. Pressure gauge connections shall be suitable for
the maximum allowable working pressure and temperature but if the temperature
exceeds 406°F, brass or copper pipe or tubing shall not be used. The
connections to the boiler, except the siphon (if used), shall not be less than
1/4 in. inside diameter standard pipe size. But where steel or wrought iron
pipe or tubing is used they shall not be less than 1/2 in. The minimum size of
a siphon (if used) shall be 1/4 in. inside diameter. 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 1-1/2 times this pressure.
Each forced-flow steam generator with no fixed steam and waterline shall be
equipped with pressure gauges or other pressure-measuring devices located as
follows:
1. At the boiler or super
heater outlet (following the last section which involves absorption of
heat).
2. At the boiler or
economizer inlet (preceding any section which involves absorption of
heat).
3. Upstream of any shutoff
valve, which may be used between any two sections of the heat-absorbing
surface.
Each high-temperature water boiler shall have a temperature
gauge so located and connected that it shall be easily readable. The
temperature gauge shall be installed so that it, at all times, indicates the
temperature in degrees Fahrenheit of the water in the boiler, at or near the
outlet connection.
L. B0-12 Stop Valves
1. Each steam outlet from a boiler (except
safety valve and water column connections) shall be fitted with a stop valve
located as close as practicable to the boiler.
2. When a stop valve is so located that water
can accumulate, ample drains shall be provided. The drainage shall be piped to
a safe location and shall not be discharged on the top of the boiler or its
setting.
3. When boilers provided
with manholes are connected to a common steam main, the steam piping connected
from each boiler shall be fitted with two stop valves having an ample free blow
drain between them. The discharge of the 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 preferably of one automatic non-return valve (set
next to the boiler) and a second valve of the outside-screw-and-yoke
type.
M. EB0-13 Blow Off
Piping
1. A blow off as required herein is
defined as a pipe connection provided with valves located in the external
piping 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 to
feed water regulators, etc., used for the purpose of determining the operating
conditions of such equipment. Piping connections used primarily for continuous
operation, such as de-concentrators on continuous blow down systems, are not
classed as blow offs, 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. A surface blow off shall not exceed 2-1/2
in. pipe size, and the internal pipe and the terminal connection for the
external pipe, 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 Fig. PG-59.1 of Section I of the ASME Code, or a flanged
connection shall be used.
3. Each
boiler, except forced-flow steam generators with no fixed steam and waterline
and high-temperature water boilers, shall have a bottom blow off outlet in
direct connection with the lowest water space practicable for external piping
conforming to PG-58.3.6 of Section I of the ASME Code.
4. All water walls and water screens which do
not drain back into the boiler, and all integral economizers, shall be equipped
with outlet connections for a blow off or drain line and conform to the
requirements of PG-58.3.6 or PG-58.3.7 of the ASME Code.
5. Except as permitted for miniature boilers,
the minimum size of pipe and fittings shall be 1 in., and the maximum size
shall be 2-1/2 in., except that for boilers with 100 sq. ft. of heating surface
or less; the minimum size of pipe and fittings may be 3/4 in.
6. Condensate return connections of the same
size or larger than the size herein specified may be used, and the blow off may
be connected to them. In such cases, the blow off shall be so located that the
connection may be completely drained.
7. A bottom blow off pipe when exposed to
direct furnace heat shall be protected by firebrick or other heat-resisting
material, which is so arranged that the pipe may be inspected. An opening in
the boiler setting for a blow off pipe shall be arranged to provide free
expansion and contraction.
N. Repairs and Renewals of Boiler Fittings
and Appliances
Whenever repairs are made to fittings or appliances or it
becomes necessary to replace them, the work shall comply with the requirements
for new installations.
O.
EB0-15 Conditions Not Covered By These Requirements
All cases not specifically covered by these requirements
shall be treated as new installations or may be referred to the chief boiler
administrator for instructions concerning the
requirements.
