| (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/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 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,
shall have at least one safety valve designed for steam service in
accordance with applicable ASME Code of Construction. The valve body
drain shall 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
shall 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 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
ASME code.
(3) Each ASME Code, Section I, process steam generator,
shall have one safety valve and if it has more than 500 square feet
(47 square meters) of bare tube water heating surface, it shall have
two or more safety valves. ASME Code, Section I, safety valves shall
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(14),
of any description shall 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/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, shall 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.
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