Techne IFB-131, Operator'S Manual

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I F B - 1 3 1 O P E R A T O R ’ S M A N U A L
PAGE 13
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.