| (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
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.
(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(14),
shall 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/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 shall 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.
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