16 Tex. Admin. Code § 65.607 - Power Boilers, Excluding Unfired Steam Boilers and Process Steam Generators
(a) Safety valves
and pressure relief valves.
(1) The use of
weighted-lever safety valves, or safety valves having either the seat or disk
of cast iron, is prohibited.
(2)
Each boiler shall have at least one safety valve and, if it has more than 500
square feet (47 square meters) of bare tube water heating surface or has
electric power input more than 1,100 kilowatts, it shall have two or more
safety valves. These valves shall be "V" stamped per ASME Code.
(3) Safety valves or pressure relief valves
shall be connected so as to stand in the upright position, with spindle
vertical. The opening or connection between the boiler and the safety valve or
pressure relief valve shall have at least the area of the valve
inlet.
(4) The valve or valves
shall be connected to the boiler, independent of any other steam connection,
and attached as close as practicable to the boiler without unnecessary
intervening pipe or fittings.
(5)
Except for changeover valves as defined in §65.2(17), other valve(s) must
not be placed:
(A) between the required
safety valve or pressure relief valve or valves and the boiler; or
(B) in the discharge pipe between the safety
valve or pressure relief valve or valves and the atmosphere.
(6) When a discharge pipe is used,
it shall be:
(A) at least full size of the
safety valve discharge; and
(B)
fitted with an open drain to prevent water lodging in the upper part of the
safety valve or discharge pipe.
(7) When an elbow is placed on a safety valve
discharge pipe:
(A) it shall be located close
to the safety valve outlet; and
(B)
the discharge pipe shall be securely anchored and
supported.
(8) In the
event multiple safety valves discharge into a common pipe, the discharge pipe
shall be sized in accordance with ASME Code, Section I, PG-71.
(9) All safety valve or pressure relief valve
discharges shall be located or piped to a safe point of discharge, clear from
walkways or platforms.
(10) If a
muffler is used on a pressure relief valve, it must have sufficient area to
prevent back pressure from interfering with the proper operation and discharge
capacity of the valve. Mufflers must not be used on high-temperature water
boilers.
(11) The safety valve
capacity of each boiler must allow the safety valve or valves to discharge all
the steam that can be generated by the boiler without allowing the pressure to
rise more than 6.0% above the highest pressure to which any valve is set, and
to no more than 6.0% above the MAWP. For forced-flow steam generators with no
fixed steam and waterline, power-actuated relieving valves may be used in
accordance with ASME Code, Section I, PG-67.
(12) One or more safety valves on every drum
type boiler shall be set at or below the MAWP. The remaining valve (s) may be
set within a range of 3.0% above the MAWP, but the range of setting of all the
drum mounted pressure relief valves on a boiler shall not exceed 10% of the
highest pressure to which any valve is set.
(13) When two 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 maximum
generating capacity of all boilers.
(14) In those cases where the boiler is
supplied with feedwater directly from water mains without the use of feeding
apparatus (not to include return traps), no safety valve shall be set at a
pressure higher than 94% of the lowest pressure obtained in the supply main
feeding the boilers.
(b)
Feedwater supply.
(1) Each boiler shall have
a feedwater supply, which will permit it to be fed at any time while under
pressure, except for automatically fired miniature boilers that meet all of the
following criteria:
(A) the boiler is "M"
stamped per ASME Code, Section I;
(B) the boiler is designed to be fed
manually;
(C) the boiler is
provided with a means to prevent cold water from entering into a hot boiler;
and
(D) the boiler is equipped with
a warning sign visible to the operator not to introduce cold feedwater into a
hot boiler.
(2) A boiler
having more than 500 square feet (47 square meters) of water heating surface,
shall have at least two means of feeding, one of which should be a pump,
injector, or inspirator. A source of feed directly from water mains at a
pressure of at least 6.0% greater than the set pressure of the safety valve
with the highest setting may be considered as one of the means of feeding.
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 shutoff of heat input if the feedwater is interrupted.
(3) Feedwater shall not be discharged close
to riveted joints of shell or furnace sheets or directly against surfaces
exposed to products of combustion or to direct radiation from the
fire.
(4) Feedwater piping to the
boiler shall be provided with a check valve near the boiler and a stop 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 stop valve on the branch to each
boiler between the check valve and the source of supply. Whenever a globe valve
is used on the feedwater piping, the inlet shall be under the disk of the
valve.
(5) 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 boiler and
the check valve, and both shall be located as close to the boiler as is
practicable. Best practice is that no stop valve be placed in the supply and
return pipe connections of a single boiler installation.
(6) Where deaerating heaters are not used,
best practice is that the temperature of the feedwater be not less than 120
degrees Fahrenheit (49 degrees Celsius), to avoid the possibility of setting up
localized stress. Where deaerating heaters are used, best practice is for the
minimum feedwater temperature be not less than 215 degrees Fahrenheit (102
degrees Celsius), so that dissolved gases may be thoroughly
released.
(c) 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 gage glass.
(2) Except for electric boilers of the
electrode type, boilers with a MAWP over 400 psig (three (3) megapascals) shall
be provided with two water gage glasses, which may be connected to a single
water column or connected directly to the drum.
(3) Two independent remote level indicators
may be provided instead of one of the two required gage glasses for boiler drum
water level indication, when the MAWP is above 400 psig (three (3)
megapascals). When both remote level indicators are in reliable operation, the
remaining gage glass may be shut off, but shall be maintained in serviceable
condition.
(4) In all installations
where direct visual observations of the water gage glass(es) cannot be made,
two remote level indicators shall be provided at operational level.
(5) The gage glass cock connections shall not
be less than 1/2 inch nominal pipe size (15 mm).
(6) No outlet connections, except for damper
regulator, feedwater regulator, drains, steam gages, or apparatus of such form
as does not permit the escape of an appreciable amount of steam or water there
from, shall be placed in the pipes connecting a water column or gage glass to a
boiler.
(7) The water column shall
be fitted with a drain cock or drain valve of at least 3/4 inch nominal pipe
size (20 mm). The water column blowdown pipe shall not be less than 3/4 inch
nominal pipe size (20 mm), and shall be piped to a safe point of
discharge.
(8) Connections from the
boiler to remote level indicators shall be at least 3/4 inch nominal pipe size
(20 mm), to and including the isolation valve, and at least 1/2 inch (13 mm) OD
tubing from the isolation valve to the remote level indicator. These
connections shall be completely independent of other connections for any
function other than water level indication.
(d) Low-water fuel cutoff and water feeding
devices.
(1) All automatically fired steam
boilers, except boilers having a constant attendant, who has no other duties
while the boiler is in operation, must be equipped with approved low-water fuel
cutoffs.
(A) These devices shall be installed
in such a manner that they cannot be rendered inoperative by the manipulation
of any manual control or regulating apparatus.
(B) In boilers with a fixed water line, the
low-water fuel cutoff devices shall be tested regularly by lowering the water
level sufficiently to shut off the fuel supply to the burner when the water
level reaches the lowest safe level for operation. Boilers that do not have a
fixed water line shall be equipped with a flow sensing device, thermal couple
or expansion ring that is listed by a nationally recognized testing agency to
prevent burner operation at a flow rate inadequate to protect the boiler unit
against overheating.
(C) The
low-water cutoff shall be rated for a pressure and temperature equal to or
greater than the MAWP and temperature of the boiler.
(D) For high-temperature water boilers
requiring forced flow circulation, an approved flow sensing device must be
installed on the outlet, as close to the boiler as possible.
(2) When a low-water fuel cutoff
and feedwater pump control is combined in a single device, an additional
separate low-water fuel cutoff shall be installed. The additional control shall
be wired in series electrically with the existing low-water fuel
cutoff.
(3) When a low-water fuel
cutoff is housed in either the water column or a separate chamber it shall be
provided with a blowdown pipe and valve not less than 3/4 inch nominal pipe
size (20 mm). The arrangement shall be such that when the water column is blown
down, the water level in it will be lowered sufficiently to activate the
lower-water fuel cutoff device.
(4)
If a water feed device is utilized, it shall be constructed to prevent
feedwater from entering the boiler through the water column or separate chamber
of the low-water fuel cutoff.
(e) Pressure gages.
(1) Each boiler shall have a pressure gage
that is readable.
(A) The dial of the pressure
gage shall be graduated to approximately double the pressure at which the
safety valve is set, but in no case, less than one and one-half times this
pressure.
(B) The pressure gage
shall be connected to the steam space, to the water column, or its steam
connection.
(C) A valve or cock
shall be placed in the gage connection adjacent to the gage.
(D) An additional valve or cock may be
located near the boiler providing it is locked or sealed in the open
position.
(E) No other shutoff
valves shall be located between the gage and the boiler.
(F) The pipe connection shall be of ample
size and arranged so that it may be cleared by blowing down.
(G) For a steam boiler, the gage or
connection shall contain a siphon or equivalent device which will develop and
maintain a water seal that will prevent steam from entering the gage
tube.
(2) Each boiler
shall have a valved connection at least 1/4 inch nominal pipe size (6 mm)
connected to the steam space for the exclusive purpose of attaching a test gage
when the boiler is in service to test the accuracy of the pressure
gage.
(f) Stop valves.
(1) Each steam outlet from a boiler (except
safety valve connections) shall be fitted with a stop valve located as close as
practicable to the boiler.
(2) When
a stop valve is located that allows water to accumulate, ample drains shall be
provided. The drain shall be piped to a safe location and shall not be
discharged on the boiler or its setting.
(3) When boilers provided with manholes or
other similar opening that permits access for human occupancy and that are
connected to a common steam main, the steam connection from each boiler shall
be fitted with two stop valves, with an ample 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. Best practice is for the first
valve to be an automatic nonreturn valve (set next to the boiler), and a second
valve of the outside-screw-and-yoke type.
(g) Blowdown connection.
(1) The construction of the setting around
each blowdown pipe shall permit free expansion and contraction. These setting
openings must be sealed without restricting the movement of the blowdown
piping.
(2) All blowdown piping,
when exposed to furnace heat, shall be protected by firebrick or other
heat-resisting material, and constructed to allow the piping to be
inspected.
(3) Each boiler shall
have a blowdown pipe, fitted with a valve or cock, in direct connection with
the lowest water space. The piping shall be run full size without the use of a
reducer or bushings and shall not be galvanized. Cocks shall be of gland or
guard type and suitable for the pressure allowed. The use of globe valves shall
be in accordance with ASME code.
(4) When the MAWP exceeds 100 psig (700
kilopascals), the piping shall be at least schedule 80 steel and shall not be
galvanized. Each blowdown pipe shall be provided with two valves or a valve and
cock, such valves and cocks shall be adequate for design conditions of the
boiler.
(5) All fittings between
the boiler and blowdown valve shall be of steel or extra-heavy malleable iron.
In case of renewal of blowdown pipe or fittings, they shall be installed in
accordance with the requirements of the applicable section of the ASME
code.
(6) It is recommended that
blowdown tanks be designed, constructed, and installed in accordance with
National Board recommended rules for boiler blowoff
equipment.
(h) Boiler
external piping. All boiler external piping, as referenced in the ASME code,
shall be examined for compliance to the boiler's code of construction and shall
be documented in the appropriate block on the inspection report.
(i) Provisions for thermal expansion for
high-temperature water boilers.
(1) An
airtight tank or other suitable air cushion that is consistent with the volume
and capacity of the system shall be installed. Expansion tanks shall be
constructed in accordance with the ASME Code, Section VIII, Division 1, and the
pressure and temperature ratings of the tank shall be equal to or greater than
the pressure and temperature ratings of the system pressure. A pressure relief
valve shall be installed with a set pressure at or below the MAWP of the
expansion tank. Alternately the boiler pressure relief valve may be used
provided the expansion tank's MAWP is equal to or greater than the set pressure
of the pressure relief valve.
(2)
Provisions shall be made for draining the tank without emptying the system,
except for pre-pressurized tanks.
(3) If the expansion tank was originally
equipped with a sight glass, the sight glass and sight glass valves shall be in
working condition at all times, and the water level shall be maintained as per
the manufacturer's recommendations.
Notes
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