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Type
of Furnace:
Horizontal tube furnace type TZF/12/125 with a water cooling
section and door assembly
Application:
Not specified
Work Tube:
Vitreous fused silica (Rotosil) 100mm bore x 1500mm long
Carbolite
accept no responsibility for the life of the work tube which can
suffer thermal shock damage during operations
Atmosphere:
Hydrogen and/or Nitrogen
Maximum
Operating Temperature:
1150°C (Hydrogen only above 750°C)
Furnace
zones:
3 zone control with re-transmission of the working set point
from the centre zone to the end zones
Heated
Length:
Nominally 915mm
Tube
Axis Height:
Nominally 1400mm
Heating
Elements:
Recralloy wire spirals cemented on to a ceramic former
Cooling:
A 600mm long double skinned cylindrical stainless steel water
cooling section to which a continuous flow of water must be applied,
is connected to the end of the work tube with a gas tight flange.
Construction:
Rolled and fabricated from stainless steel sheet and fitted
with a outer mesh cover and mesh end guards.
The supporting framework is made from rolled hollow section
steel, which is fitted with painted steel panels.
Uniform
Zone:
450mm long ±
5°C. measured in an empty work tube with the tube ends plugged.
Temperature
Sensors:
3 off type ‘R’ thermocouples for control, 1 off
thermocouple for independent over-temperature protection
emperature
Control:
3 off Eurotherm 815S microprocessor based PID controllers with
digital display of the measured value. The centre zone controller has
a “Ramp Rate” facility, which protect the work-tube from damage
due to thermal shock on heating and cooling. The working set-point is
re-transmitted from the centre zone to the remote inputs of the end
zone controllers.
A fail-safe “Full Scale Low” alarm relay is fitted to the
centre zone controller, preventing the Hydrogen solenoid valve from
opening whilst the furnace is below 750°C
A fail safe “Full Scale High” alarm relay is fitted to the
centre zone controller, this will activate the process timer as the
furnace approaches the set point.
Over
Temperature Protection:
1 off Eurotherm 106 process alarm instrument operating a safety
contactor with visual alarm and manual reset
Power
Control:
3 off Eurotherm 425 SSC thyristors with protection against high
current and voltage transients
Timer:
An analogue countdown time with 5 pre-selectable ranges and
audible alarm is activated by the “Full Scale High” alarm of the
centre zone controller.
Location
of Controls:
Located in the furnace supporting framework.
Furnace
Rating:
7kW
Power
Supply Requirements:
240v, 50Hz, single phase supply with neutral and earth, fused
and isolated for 35 amps.
Loading/Unloading:
The loading/unloading of the furnace charge is carried our
manually through the flap type door. It should be carried out with a
suitable push rod made from a non-conductive material e.g. high purity
alumina.
Gas
Control/Alarm System:
The Nitrogen and Hydrogen process gases are controlled by
separate flowmeters scaled at 0-50 litres/minute. They enter the
furnace through a single inlet on the blank end of the work tube.
Because the furnace can operate with a Hydrogen atmosphere
there are several ‘fail safe’ safety interlock relay contacts,
which must be closed before the Hydrogen can be allowed in to the
furnace work tube.
The Nitrogen and Hydrogen gas supplies must be nominally 5 psi
in order to close factory pre-set pressure switches.
The Honeywell UV detector fitted adjacent to the work tube
access door must be able to detect a flame from the Natural gas
burner.
Failure to satisfy the above conditions will activate a visual
and audible alarm and will automatically close the Hydrogen supply and
open the Nitrogen “safety purge”.
Water
Cooling:
A solenoid valve will be opened admitting cooling water to the
stainless steel water jacket whenever the temperature of the water in
the cooling section exceeds 50°C.
Approximate
Overall Dimensions:
1620mm high x 500mm wide x 2350mm long
Additional
Supply Requirements:
A “Mains” water supply of nominally 1-3 l/min, suitable for
connection to a 10mm compression fitting.
Hydrogen and Nitrogen process gas supplies isolated and
regulated for nominally 5 psi, suitable for connection to 8mm
compression fittings
A natural gas supply isolated and suitably regulated, suitable
for connection to a 6mm compression fitting.
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