Techne IFB-51 Bedienungsanleitung Seite 25

The figures quoted are approximate and may need to be varied depending upon the work load, e g the
bath may have to be over fluidised to avoid the creation of dead spots above an immersed object. For
details of how to adjust the fluidising air flow rate when using the automatic air control system, see Item
c) of the Fault Finding Section of this manual.
To safeguard the fluidised bath from damage, two safety features are included in the control console: an
adjustable over temperature cut-out which guards against controller failure, and an air pressure switch
which inhibits operation if the compressed air supply to the fluidised bath fails. Both of these devices
isolate the electrical supply to the heater elements and illuminate the cut-out indicator in a fault
condition. The over temperature cut-out is factory preset at 630°C. Under no circumstances should this
setting be increased, but lower limits may be set to safeguard particular processes in the fluidisation
bath.
If the fluidised bath is to be used to process items that may emit toxic or inflammable fumes, it is essential
that an adequate fume extraction system be installed. Details of fume cleaning equipment are contained
in the following section of this manual.
The extraction system must be adjusted during initial operation for optimum extraction in line with the
following instructions:
a) Heat the fluidised bath to the operating temperature a recommended later in this manual, ensuring
that the fluidising air flow rate is adjusted in accordance with the above table.
b) Switch on the fume extraction system.
c) Immerse a typical component that is to be treated into the fluidised bath; do not exceed the stated
loading capacity, see Technical Specification for details.
d) Adjust the overall fume extraction rate by adjusting the setting of the damper valves built into the
fume extraction system so that adequate fume removal occurs over the surface of the fluidised bath.
The velocity of the extraction system should be just sufficient to entrain the maximum quantity of
fumes produced above the bath. If high extraction velocity misused, an excessive amount of
fluidising medium will be entrained by the extraction system.
e) Measure the fume concentration within the fume extraction system using an explosimeter and
ensure that the Lower Explosive Limit (LEL) is not exceeded. The fume concentration should be
diluted by fitting a dilution tee into the extraction ductwork directly after the fluidising bath. Air may
then be induced into the system to dilute the effluent gases. It is recommended that the maximum
fume concentration be less than 25% of the LEL.
f) Measure the fume concentration in the working environment adjacent to the fluidised bath using
suitable gas analysis equipment such as "Drager" tubes, to ensure that any toxic fumes generated
within the fluidised bath have been diluted so that the fume concentration is below the threshold
limit value. Recommended Threshold Limit Values (TLVs) are available in publications such as the
Health and Safety Executives Guidance Note EH15/76 in the UK, a copy of which is available from
Techne on request.
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