(a) Steam Heating Boilers.
(1) Safety valves.
(A) Each steam boiler shall have one or more safety
valves, that are identified with applicable designator with the ASME
Certification Mark of the spring pop type, adjusted and sealed to
discharge at a pressure not to exceed 15 psig (103 kilopascals). Seals
shall be attached in a manner to prevent the valve from being taken
apart without breaking the seal. The safety valves shall be arranged
so that they cannot be reset to relieve at a higher pressure than
the MAWP of the boiler. A body drain connection below seat level shall
be provided. For valves exceeding 2 1/2 inch nominal pipe size (65
mm), the drain hole or holes shall be tapped not less than 3/8 inch
nominal pipe size (10 mm). For valves 2 1/2 inch nominal pipe size
(65 mm) or less, the drain hole shall not be less than 1/4 inch (6
mm) in diameter.
(B) Each safety valve 3/4 inch nominal pipe size (20
mm) or over, used on a steam boiler, shall have a substantial lifting
device, which will positively lift the disk from its seat at least
1/16 inch (1.6 mm), when there is no pressure on the boiler. The seats
and disks shall be of suitable material to resist corrosion.
(C) No safety valve for a steam boiler shall be smaller
than 1/2 inch nominal pipe size (15 mm). No safety valve shall be
larger than 4 1/2 inches nominal pipe size (15 mm). The inlet opening
shall have an inside diameter approximately equal to, or greater than,
the seat diameter.
(D) The minimum relieving capacity of valve or valves
shall be governed by the capacity marking on the boiler.
(E) The minimum valve capacity in pounds per hour shall
be the greater of that determined by dividing the maximum Btu output
at the boiler nozzle obtained by the firing of any fuel, for which
the unit is installed by 1,000, or shall be determined on the basis
of the pounds of steam generated per hour, per square foot of boiler
heating surface as given in §65.615, Exhibit 7. For cast iron
boilers, the minimum valve capacity shall be determined by the maximum
output method. In every case, the safety valve capacity for each steam
boiler shall be such that with the fuel burning equipment installed,
and operated at maximum capacity, the pressure cannot rise more than
5psig (35 kilopascals) above the MAWP.
(F) Safety valve piping. No valve shall be placed between
the safety valve and the boiler or on the discharge pipe between the
safety valve and the atmosphere. When a discharge pipe is used, it
shall be full size and fitted with an open drain to prevent water
from lodging in the upper part of the safety valve or pressure relief
valve or in the discharge pipe. When an elbow is placed on the safety
valve discharge pipe, it shall be located close to the valve outlet.
The discharge pipe shall be securely anchored and supported, independent
of the valve. 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.
(G) Safety valves and pressure relief valves shall
be installed on the boiler with spindles positioned vertically. The
opening or connection between the boiler and any safety valve or pressure
relief valve shall have at least the area of the valve inlet.
(2) Feedwater connections.
(A) Feedwater or water treatment shall be introduced
into a boiler through the return piping system or through an independent
feedwater connection which does not discharge against parts of the
boiler exposed to direct radiant heat from the fire. Feedwater or
water treatment shall not be introduced through openings or connections
provided for inspection or cleaning, safety valve, surface blowoff,
water column, water gage glass, pressure gage, or temperature gage.
(B) Feedwater pipe shall be provided with a check valve
near the boiler and a stop valve or cock between the check valve and
the boiler or return pipe system.
(3) Low-water fuel cutoffs and water feeding devices.
(A) All automatically fired steam boilers, except boilers
having a constant attendant, who has no other duties while the boiler
is in operation, shall be equipped with approved automatic low-water
fuel cutoffs installed in such a manner that they cannot be rendered
inoperative by the manipulation of any manual control or regulating
apparatus.
(B) The MAWP of all low water fuel cutoff devices shall
be set at or above the boiler stamped MAWP.
(C) When low-water fuel cutoff and feedwater pump controls
are 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.
(D) 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 low-water fuel cutoff device.
(E) 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.
(4) Pressure gages.
(A) Each steam heating boiler shall have a pressure
gage connected to the device exterior to the boiler. The gage shall
be of sufficient capacity to keep the gage tube filled with water
and arranged so that the gage cannot be shut off from the boiler except
by a cock with tee or lever handle placed in a pipe near the gage.
The handle of the cock shall be parallel to the pipe in which it is
located when the cock is open.
(B) The scale on the dial of a steam heating boiler
pressure gage shall be graduated to not less than 30 psig (207kilopascals)
nor more than 60 psig (414 kilopascals). The travel of the pointer
from zero to 30 psig (207 kilopascals) pressure shall be at least
three inches.
(5) Stop valves.
(A) Single steam heating boilers. When a stop valve
is used in the supply pipe connection of a single steam heating boiler,
there shall be one used in the return pipe connection.
(B) Supply and return line. Each supply and return
line to a steam heating boiler, which may be entered while adjacent
boilers are in operation, shall be fitted with either two stop valves
with ample drain between or a stop valve and figure 8 blank. The blank
shall be installed between the stop valve and the boiler.
(C) Type of stop valve. When stop valves over two inches
in size are used, they shall be of the outside screw-and-yoke rising
stem type or of such other type as to indicate at a distance whether
it is closed or open by the position of its stem or other operating
mechanism. The wheel may be carried either on the yoke or attached
to the stem. If the valve is of the plug cock type, it shall be fitted
with a slow opening mechanism and an indicating device and the plug
shall be held in place by a guard or gland.
(6) Bottom blowdown or drain valve.
(A) Bottom blowoff valve. Each steam heating boiler
shall have a bottom blowoff connection fitted with a valve or cock,
connected to the lowest water space practicable with a minimum size
as shown in §65.615, Exhibit 8. The discharge piping shall be
full size to the point of discharge. Boilers having a capacity of
25 gallons (95 liters) or less are exempt from these requirements.
(B) Drain valve. Each boiler shall have one or more
drain connections, fitted with valves or cocks connecting to the lowest
water containing spaces. The minimum size of the drain piping, valves,
and cocks shall be 3/4 inch nominal pipe size (20 mm). The discharge
piping shall be full size to the point of discharge. When the blowoff
connection is located at the lowest water containing space, a separate
drain connection is not required.
(C) Minimum pressure rating. The minimum pressure rating
of valves and cocks used for blowoff or drain purposes shall be at
least equal to the pressure stamped on the boiler, but in no case
less than 30 psig (207 kilopascals). The temperature rating of such
valves and cocks shall not be less than 250 degrees Fahrenheit (121
degrees Celsius).
(7) Water gage glasses.
(A) Each steam heating boiler shall have one or more
water gage glasses attached to the water column or boiler, by means
of valved fittings not less than 1/2 inch nominal pipe size (15 mm).
The lower fitting shall have a drain valve of the straightway type,
with opening not less than 1/4 inch (8 mm) diameter to facilitate
cleaning. Gage glass replacement shall be possible under pressure.
(B) Transparent material, other than glass, may be
used for the water gage, provided that the material will remain transparent
and has proved suitable for the pressure, temperature, and corrosive
conditions encountered in service.
(8) Piping, Fittings and Valves.
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