multiport cast iron construction and provide for even heating of
radiant elements. Heater design shall be essentially the same for
undercar and sidecar heaters, with heat transmitted to hopper car
by both radiation and convection. Design burner and radiant
element for radiation being the primary mode of heat transfer.
Make radiant element over the burner of a heavy
corrosion-resistant metal material. Design burner to operate on
[No. 2 fuel oil] [natural gas] [liquified petroleum gas], and such
that open flame from combustion will not extend beyond the emitter
surface either during normal operation or in the event of emitter
deterioration or burnout. Provide shields where necessary to
direct radiation and hot exhaust gases to hopper car surface.
Provide means for shielding car air hoses, air brake equipment,
and bearings from excessive heat. Provide each heater with
individual heater control boxes constructed as to provide positive
air pressure inside control box. Control boxes shall contain
mixing valve for maintaining proper gas-air ratio for satisfactory
combustion.
Locate gas and air piping connections for easy
removal of individual burners. Deliver combustion air to heaters
by means of pressure blowers which take fresh air from outside
thawing area to ensure continued satisfactory combustion of
gaseous fuels. Factory wire and assemble thawing units, control
panels, blowers, and zone controls. Fuel system and burner
control for oil fired units shall be as specified under paragraph
entitled "Pit-Type Railroad Hopper Car Thawing System" above.
b.
Burner Controls (for gas fired units): Burners shall be
electrically ignited with controls meeting I.R.I. requirements.
Provide a gas pressure regulator for serving not more than eight
individual burners. Regulator shall reduce gas pressure in supply
line to pressure required for burners. Provide each burner with
an air regulating valve for fuel-air ratio adjustment. Regulating
valve shall contain positive vibration-proof locking device for
maintaining critical adjustment.
c.
Control Panel: Provide centrally located control panel with panel
front having a graphic display of the thawing system. Display
shall be approximately to scale and coordinated with control and
light indication for combustion air blowers and on-off control of
individual heaters. Provide a modulating control for each heater
to regulate heat output to suit the operating requirements. Panel
shall be [NEMA 12] [NEMA 3R-8], dust-tight enclosure with internal
equipment and wiring accessible from the panel front. Provide
nameplates on panel front to designate function of switches and
indicating lights. Controls shall be suitable for [_____] volt,
[_____] phase, 60 Hz operation. Provide and mark terminals for
connections, with the exception of the neutral. Terminal blocks
shall be 600 volt rated. Control relays shall have convertible
contacts and shall have rating suitable for intended service but
not less than 10 amp, 600 volt rating. Components shall be an
industrial design of the oiltight type. Connections to the panel
shall be watertight. Motor starters for combustion air blowers
shall be installed in each respective blower cabinet.
[d.
Thawing unit may be an electric radiant heat thawing unit which
includes self-contained heater banks such as under-car outside the
rail heater sections, lower side car heater sections and vertical
side car heater sections, with reflectors, hinged cover,
waterproof and weatherproof wired terminal blocks and zone
SECTION 15502N
Page 96
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