| (A) All piping, fittings and valves on the steam line,
shall have a pressure rating equal to or greater than the MAWP of
the boiler and a temperature rating of no less than 250 degrees Fahrenheit
(121 degrees Celsius).
(B) All piping, fittings and valves other than the
steam line, shall have a minimum pressure and temperature rating equal
to or greater than the maximum expected pressure and temperature that
may be reached.
(b) Hot Water Heating Boilers.
(1) Pressure relief valves.
(A) Each hot water heating boiler shall have at least
one pressure relief valve, of the automatic reseating type, identified
with the ASME Certification mark with the "V" or "HV" designator ASME
Code Symbol, and set to relieve at or below the MAWP of the boiler.
(B) When more than one pressure relief valve is used
on a hot water heating boiler, the additional valve or valves shall
have a set pressure within a range not to exceed 6 psig (42 kilopascals)
above the MAWP of the boiler up to and including 60 psig (414 kilopascals),
and 5.0% for those having a MAWP exceeding 60 psig (414 kilopascals).
(C) Pressure relief valves shall be spring loaded and
shall be set and sealed, so that they cannot be reset without breaking
the seal. 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 of 2 1/2 inch nominal pipe size (65 mm) or
less, the drain hole shall not be less than 1/4 inch (6 mm) diameter.
(D) Each pressure relief valve 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.
(E) Seats and disks of pressure relief valves shall
be made of a suitable material to resist corrosion. No materials likely
to fail due to deterioration or vulcanization, when subjected to saturated
steam temperature corresponding to capacity test pressure, shall be
used for any part.
(F) No pressure relief valve shall be smaller than
3/4 inch nominal pipe size (20 mm) nor larger than 4 1/2 inch nominal
pipe size (115 mm) except that boilers having a heat input not greater
than 15,000 Btu/hr (4.4 kilowatts) may be equipped with a rated pressure
relief valve of 1/2 inch nominal pipe size (15 mm). The inlet opening
shall have an inside diameter approximately equal to, or greater than,
the seat diameter. In no case shall the minimum opening through any
part of the valve be less than 1/4 inch (6 mm) diameter or its equivalent
area.
(G) The required steam relieving capacity, in pounds
per hour, of the pressure relieving device or devices on a boiler
shall be the greater of that determined by dividing the maximum output
in Btu 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 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.
(H) In every case, the pressure relief valve capacity
for each boiler with a single pressure relief valve shall be such
that, with the fuel burning equipment installed and operated at maximum
capacity, the pressure cannot rise more than 10% above the MAWP. When
more than one pressure relief valve is used, the overpressure shall
be limited to 10% above the set pressure of the highest set valve.
(I) Pressure relief valve piping. No valve shall be
placed between the pressure relief valve and the boiler or on the
discharge pipe between the pressure relief valve and the drain. 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
pressure relief valve or in the discharge pipe. When an elbow is placed
on the pressure relief 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. Mufflers shall not be used
on hot water heating boilers.
(J) Pressure relief valves and safety valves shall
be installed on the boiler with spindles positioned vertically. The
opening or connection between the boiler and any pressure relief valve
or safety valve shall have at least the area of the valve inlet.
(2) Makeup water connections.
(A) Makeup water or water treatment shall be introduced
into a boiler through the return piping system or through an independent
makeup water connection, which does not discharge against parts of
the boiler exposed to direct radiant heat from the fire. Makeup water
or water treatment shall not be introduced through openings or connections
provided for inspection or cleaning, pressure relief valve, pressure
gage, or temperature gage.
(B) Makeup water 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 between the check valve and the piping system.
(3) Low-water fuel cutoffs and water feeding devices.
(A) All automatically fired hot water heating boilers
shall have an automatic low-water fuel cutoff that has been designed
for hot water service, and it shall be so located as to automatically
cut off the fuel supply when the surface of the water falls to a level
below the normal waterline established.
(B) The MAWP of all low water fuel cutoff and flow
sensing 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) As there is no normal water line to be maintained
in a hot water heating boiler, any location of the low-water fuel
cutoff above the lowest safe water level established by the boiler
manufacturer is satisfactory.
(F) All automatically fired hot water heating boilers,
when installed in a forced circulation system and not under continuous
attendance, shall be equipped in the manner described in this subsection.
A coil-type boiler or a water-tube boiler requiring forced circulation
to prevent overheating of the coils or tubes shall have a flow sensing
device which is listed by a nationally recognized testing agency to
prevent burner operation at a flow rate inadequate to protect the
boiler unit against overheating.
(G) 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 and Temperature gages.
(A) Each hot water heating boiler shall have a pressure
or altitude gage connected to it or to its flow connection, which
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 the pressure or altitude
gage shall be graduated to not less than 1 1/2 nor more than 3 1/2
times the pressure at which the pressure relief valve is set. The
gage shall be provided with effective stops for the indicating pointer
at the zero point and at the maximum pressure point.
(C) Piping and tubing for pressure or altitude gage
connections shall be of nonferrous metal when smaller than 1 inch
nominal pipe size (25 mm).
(D) Each hot water heating boiler shall have a thermometer
or temperature gage located and connected, that it shall be readable,
and shall be located so that it shall at all times indicate the temperature
of the water in the boiler at or near the outlet. If placed on the
outlet piping, it must be located between the stop valve and the boiler.
(5) Stop valves.
(A) Stop valves shall be located at an accessible point
in the supply and return pipe connections near the boiler nozzle of
a single hot water heating boiler installation to permit draining
the boiler without emptying the system.
(B) When the boiler is located above the system and
can be drained without draining the system, stop valves may be eliminated.
Cont'd... |
