Fault Finding - Techne IFB-201 Operator's Manual

Fault Finding

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 630ºC. 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. Four heater elements are
fitted which produce a total heater power of 9kW. 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. The
heater elements are of the semi-embedded type.
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. Ensure that the air
pressure regulator is set at 204kPa (30 psi). If the fluidisation in the bath does not
produce satisfactory results when using the correct air flow rates, the condition of the
porous plate in the base of the fluidised bath must be suspected. An initial remedy is to
operate the fluidised bath at approximately 550oC for a period of at least one hour to
allow any accumulated residue in the bath to be decomposed. However, if the fault
continues the bath should be emptied and the porous plate examined.
The fluidised bath must only be emptied when the bath is cold. To empty the bath, use a
scoop to remove the alundum, when the unit is fluidised. A small quantity of fluidising
medium will remain in the base of the bath; this should be removed using a vacuum
cleaner. When the bath is empty, the stainless steel porous plate may be examined for
any sign of damage caused by the accumulation of plastic residue, distortion, or
corrosion. Partially blocked areas of the porous plate can be detected if the bath is
fluidised with a small quantity of fresh fluidising medium. If the porous plate assembly is
blocked any residue on the bolt heads can be chipped off. The bolt heads should be
rotated to ensure all bolts move freely and allow full air flow through the plate.
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