Fault Finding - Techne IFB-121 Operator's Manual

Any service or repair work should only be carried out by a trained electronic or electro mechanical
technicians. Untrained personnel should not attempt to dismantle this equipment.
a) If the cut-out indicator fails to extinguish when the reset switch is depressed, check the temperature
of the fluidised bath to determine whether the bath has overheated and operated the temperature
cut-out. Check the setting of the over temperature cut-out which is situated within the electrical
control console. The over temperature cut-out is factory set to a maximum temperature of 630°C.
The cut-out can be re-set by depressing the red knob on the bottom of the cut-out.
To over-ride the door safety switch pull the knob down slightly and out.
Also check that compressed air is being supplied to the fluidised bath and that the air pressure
switch is being held in the on position. When operating correctly the air pressure regulator situated
within the pneumatic control console should be set at 204k Pa (30psi) and the bath should be
fluidised.
b) If the fluidised bath fails to reach its operating temperature or the heat-up rate decreases, check the
level of fluidisation. Where an air flowmeter is fitted, check that the air flow rate agrees with the
recommended values, and in any case check that the fluidised bed is evenly fluidised with bubbles
of approximately 50mm diameter.
Also check that the heater elements are functioning correctly. Three heater elements are fitted which
produce a total heater power of 6kW. The heater elements are individually terminated within the
control console (see attached circuit diagrams for wiring details).
To inspect the heater elements, remove the inner container from the outer wrapper, then remove
the three layers of thermal insulation that surround the fluidised bath. The heater elements are of
the ceramic knuckle type, each element being clamped to the inner container. To remove an
element, disconnect the two lead wires from the terminal strip and unbolt the heater clamps.
Before fitting a new heater element, inspect the walls of the inner container to ensure the walls are
not deformed. It is vital that the heater element is in close contact with the walls of the container.
Any surface irregularities should be treated before a new element is fitted.
Reassemble the unit in reverse order, ensuring that the new heater element is bolted tightly to the
inner container.
c) If the fluidisation within the bath deteriorates, check the compressed air supply and the air filter
assembly. Replace the air filter elements if necessary. Where a flowmeter is fitted, check the air flow
rates correspond with the recommended values. If an automatic fluidising air control system is fitted
and the air flow rates do not agree with the values, re-adjust the system in accordance with the
following:-
i) Ensure that the air pressure regulator is set at 204kPa (30 psi).
ii) FOR UNITS UP TO ISSUE/5 (with two contactor system).
Adjust the set point of the automatic air control temperature monitor which is located within the
electrical console so that both of the air control solenoid valves are closed. The automatic air
control temperature monitor is the right hand monitor.
iii) Adjust the manual valve at the bottom of the pneumatic control console adjacent to the air filter
assembly until the indicated air flow rate is approximately 70 l/min.
iv) Reset the right hand temperature monitor to a temperature of 400°C which will energise the
lower solenoid valve. Adjust the central valve until the total indicated airflow rate is
approximately 110 l/min.

FAULT FINDING

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