16 Tex. Admin. Code § 65.609 - Process Steam Generators
(a) Some process
steam generators referred to in §65.2 are shown in §65.615, Exhibits
4 and 5.
(b) The steam collection
or liberation drums of a process steam generator shall be constructed in
accordance with the American Society of Mechanical Engineers (ASME) Section
VIII, Division 1, Division 2, or Division 3. As an alternate, the process steam
generator may be constructed to ASME Code, Section I.
(c) When the owner or operator elects to
construct a process steam generator to ASME Code, Section I, the limits as
shown in §65.615, Exhibits 4 and 5, are as defined in the rules of ASME
Code, Section I.
(d) 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 or Division 2, steam collection or
liberation drum of a process steam generator, must have at least one safety
valve designed for steam service in accordance with applicable ASME Code of
Construction. The valve body drain must be open and piped to a safe point of
discharge.
(A) The installation of full-area
stop valves between the steam collection or liberation drum of a process steam
generator and the safety valve is permitted as depicted in §65.615,
Exhibits 4 and 5. A full-area stop valve may be installed on the discharge of
the safety valve when connected to a common header. Stop valves must be car
sealed or locked in the open position.
(B) One or more safety valves on every steam
collection or liberation drum of a process steam generator must be set at or
below the MAWP. The remaining valves, if any, must be set within the range
specified and have the capacity required by the applicable ASME Code.
(3) Each ASME Code, Section I,
process steam generator, 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. ASME Code, Section I, safety valves must be
applicably stamped.
(A) The valve or valves
shall be connected to the steam collection or liberation drum of the process
steam generator, independent of any other steam connection, and attached as
close as practicable to the steam collection or liberation drum without
unnecessary intervening pipe or fittings.
(B) No valves, except as defined in
§65.2(17), of any description may be placed between the required safety
valve or pressure relief valve or valves and the steam collection or liberation
drum, nor on the discharge pipe between the safety valve or pressure relief
valve and the atmosphere.
(C) The
safety valve capacity of each process steam generator, shall allow the safety
valve or valves to discharge all the steam that can be generated by the process
steam generator 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 steam collection or
liberation drums of process steam generators, operating at different pressures
and safety valve settings are interconnected, the lower pressure process steam
generator(s) or interconnected piping shall be equipped with safety valves of
sufficient capacity to prevent overpressure, considering the maximum generating
capacity of all of the process steam generators.
(6) Safety valve and pressure relief valve
mountings.
(A) For ASME Code, Section I
installations, 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.
(B) For ASME Code, Section VIII, Division 1
or Division 2 installations, safety valves or 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.
(e) Feedwater supply.
(1) Each steam collection or liberation drum
of a process steam generator shall have a feedwater supply which will permit it
to be fed at any time while under pressure.
(2) Feedwater piping to a process steam
generator constructed to ASME Code, Section I, shall be provided with a check
valve near the process steam generator and a stop valve or cock between the
check valve and the process steam generator. When two or more process steam
generators are fed from a common source there shall also be a stop valve on the
branch to each process steam generator 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,
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 that the
minimum feedwater temperature be not less than 215 degrees Fahrenheit (102
degrees Celsius), so that dissolved gases may be thoroughly released.
(f) Water level indicators.
(1) ASME Code, Section I, process steam
generators 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 process steam generator
is in service.
(2) Each steam
collection or liberation drum of an ASME Code, Section VIII, Division 1,
Division 2, or Division 3 process steam generator, irrespective of pressure and
temperature, as shown in § 65.615, Exhibits 4 and 5, 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 process steam generator 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 regulator, 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 on the pipes connecting a water column or gage glass on the steam
collection or liberation drum of a process steam generator.
(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 steam collection or
liberation drum of a process steam generator 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.
(g) 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 process steam
generator. All installed low water cutoffs, alarms and feeding devices, must be
designed for a pressure and temperature equal to or greater than the MAWP and
temperature of the process steam generator steam collection or liberation
drum.
(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 a steam collection or liberation
drum of a process steam generator be installed in a system without a local and
constant attendant, and it is not a failsafe design, it shall be provided with
a low-water cutoff as required for power boilers.
(h) Pressure gages.
(1) Each steam collection or liberation drum
of a process steam generator shall have a pressure-indicating device that is
readable from the primary operating station. The range 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-indicating
device shall be connected to the steam space, or 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 steam
collection or liberation drum of the process steam generator. No other shutoff
valves shall be located between the gage and the steam collection or liberation
drum of the process steam generator. The pipe connection shall be of ample size
and arranged so that it may be cleared by blowing down or flushing. The
pressure-indicating device shall be provided with a siphon or equivalent
device, which will develop and maintain a water seal that will prevent steam
from entering the pressure-indicating device.
(2) Each steam collection or liberation drum
of a process steam generator must have a valved connection at least 1/4 inch
nominal pipe size (8 mm) connected to the steam space for the purpose of
attaching a test gage when the process steam generator is in service, to test
the accuracy of the pressure-indicating device.
(i) Stop valves.
(1) Each steam outlet from an ASME Code,
Section I, process steam generator, shall be fitted with a stop valve located
as close as practicable to the steam collection or liberation drum of the
process steam generator.
(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 process steam generator 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
State regulations are updated quarterly; we currently have two versions available. Below is a comparison between our most recent version and the prior quarterly release. More comparison features will be added as we have more versions to compare.
No prior version found.