16 Tex. Admin. Code § 65.608 - Unfired Steam Boilers
(a) Unfired steam
boilers referred to in § 65.2 are shown in § 65.615, Exhibits 2 and
3.
(b) Unfired steam boilers shall
be constructed in accordance with ASME Code, Section I, or ASME Code, Section
VIII, Division 1, 2 or 3.
(1) Unfired steam
boilers constructed to ASME Code, Section VIII, Division 1, 2 or 3, shall meet
jurisdictional limits established in § 65.615, Exhibit 2.
(2) Unfired steam boilers constructed to ASME
Code, Section I, shall meet jurisdictional limits established in § 65.615,
Exhibit 3.
(c) 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 ASME Code, Section VIII, Division 1,
2 or 3, unfired steam boiler shall:
(A) have
all pressure relief valves fabricated in accordance with ASME Code, Section
VIII, Division 1 or Section I; and
(B) have at least one pressure relief
valve.
(C) Isolation valves may be
installed between the unfired steam boiler and the safety valve in accordance
with § 65.615, Exhibit 2.
(D)
Full-area stop valves may be installed on the inlet side of a safety valve in
accordance with § 65.615, Exhibit 2. A full-area stop valve may be
installed on the discharge of the safety valve when connected to a common
header. Stop valves shall be car sealed or locked in the open
position.
(E) One or more safety
valves on every unfired steam boiler shall be set at or below the MAWP. The
remaining valves, if any, shall be set within the range specified and have the
capacity required by the applicable section of the ASME Code.
(3) Each ASME Code, Section I,
unfired steam boiler must have one safety valve and if it has more than 500
square feet (47 square meters) of bare tube water heating surface, it must have
two or more safety valves.
(A) 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.
(B) Valves, except a changeover valve as
defined in §65.2(17), must not be placed between the required safety valve
or pressure relief valve or valves and the boiler nor on the discharge pipe
between the safety valve or pressure relief valve and the atmosphere.
(C) The safety valve capacity of each unfired
steam 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.
(4) When a discharge pipe open to the
atmosphere is used, it shall be at least 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 discharge piping. The drain or drains shall be
piped to a safe point of discharge. When an elbow or fitting is installed on
the discharge pipe it shall be located close to the safety valve outlet. The
discharge pipe shall be securely anchored and supported. All safety valve
discharges shall be located or piped to a safe point of discharge clear from
walkways or platforms. If a muffler is used on a pressure relief valve, it
shall have sufficient area to prevent back pressure from interfering with the
proper operation and discharge capacity of the valve.
(5) When two or more unfired steam 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.
(6) Safety valve and pressure relief valve
mountings.
(A) For ASME Code, Section I
installations, 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 pressure relief valve shall have at least the area of the valve
inlet.
(B) For ASME Code, Section
VIII, Division 1 installations, pressure relief valves normally should be
installed in the upright position, with spindle vertical. Where space or piping
configurations preclude such an installation, the valve may be installed in
other than the vertical position, provided that:
(i) the valve design is satisfactory for such
position;
(ii) the media is such
that material will not accumulate at the inlet of the valve; and
(iii) drainage of the discharge side of the
valve body and discharge piping is adequate.
(d) Feedwater supply.
(1) Each unfired steam boiler shall have a
feedwater supply which will permit it to be fed at any time while under
pressure.
(2) Feedwater piping to
the unfired steam boiler constructed to ASME Code, Section I, 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.
(3) Where deaerating heaters are not used, it
is recommended 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, it is recommended that the
minimum feedwater temperature be not less than 215 degrees Fahrenheit (102
degrees Celsius), so that dissolved gases may be thoroughly released.
(e) Water level indicators.
(1) ASME Code, Section I, unfired steam
boilers with a MAWP of 400 psig (three (3) megapascals) or less, shall have at
least one gage glass. For a MAWP over 400 psig (three (3) megapascals), shall
have two required gage glasses. When two gage glasses are required, one of the
gage glasses may be replaced by two independent remote level indicators that
are maintained in simultaneous operation while the boiler is in
service.
(2) Each steam drum of an
ASME Code, Section VIII, Division 1 unfired steam boiler, irrespective of
pressure and temperature, shall be provided with one direct reading water level
indicator (water gage glass), or two independent remote level indicators, that
are maintained in simultaneous operation while the boiler is in
service.
(3) 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.
(4) The gage glass cock connections shall not
be less than 1/2 inch nominal pipe size (15 mm).
(5) No outlet connections, except for
feedwater regulators, drains, steam gages, or apparatus of such form as does
not permit the escape of an appreciable amount of steam or water therefrom,
shall be placed in the pipes connecting a water column or gage glass to a
boiler.
(6) 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.
(7) Connections from the
unfired steam 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.
(f) Low-water cutoffs, alarms and
feed regulating devices.
(1) The owner or
operator is responsible for the design and installation of any low water
protection devices as required to prevent damage to the unfired steam boiler.
All installed low water cutoffs, alarms and feeding devices must be designed
for pressure and temperature equal to or greater than the MAWP of the unfired
steam boiler.
(2) When a low-water
cutoff, and/or alarm 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 low-water cutoff and/or alarm device.
(3) Should an unfired steam boiler be
installed in a system without a local and constant attendant, and it is not a
fail-safe design, it shall be provided with a low-water cutoff as required for
power boilers.
(g)
Pressure gages.
(1) Each unfired steam boiler
shall have a pressure gage that is readable. 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.
The pressure gage shall be connected to the steam space, to the water column,
or its steam connection. A valve or cock shall be placed in the gage connection
adjacent to the gage. 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 gage and the boiler. The pipe connection
shall be of ample size and arranged so that it may be cleared by blowing down.
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 unfired steam
boiler, must have a valved connection at least 1/4 inch nominal pipe size (8
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.
(h) Stop valves.
(1) Each steam outlet from an ASME Code,
Section I unfired steam boiler, shall be fitted with a stop valve located as
close as practicable to the boiler.
(2) When a stop valve is located such that it
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 that are
provided with manholes or other similar openings that permit access for human
occupancy are connected to a common steam main, the owner or operator shall
ensure that the boiler to which entry is being made is completely isolated from
the steam main. This may be accomplished with the use of two stop valves with
an ample drain between them, with a full isolation blind or removal of piping
such that the boiler is no longer connected to the steam main.
Notes
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