Cole Parmer Techne IFB-201, Инструкция по эксплуатации

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e) Measure the fume concentration within the fume extraction system using an explosimeter and ensure
that the Lower Explosimeter Limit (LEL) is not exceeded. The fume concentration may be diluted by
fitting a dilution tee into the extraction ductwork directly after the fluidised bath. Air may then be
induced into the system to dilute the ef fluent 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.The
figu res 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.
Fume Ignition
Spontaneous ignition may occur above the surface of the fluidised bath or within the exhaust ductwork
if the concentration exceeds the lower explosive limit.
The fume concentration is dependent upon the rate of fume production in the fluidised bath and the
level of dilution achieved by entraining air from above the bath or through the dilution tee.
The rate of fume production is dependent upon the type and amount of material being treated and the
temperature of the bath.
To ensure that the concentration of inflammable fumes is below the lower explosive limit, ensure that
the amount of combustible material immersed in the bath at any one time is within the design capacity
of the extraction system. Ensure that the temperature of the bath is at the minimum level at which
satisfactory results can be achieved. Increased working temperatures result in increased fume
concentration. By way of example, an extraction rate of 2m /min is required to ensure that the fume
concentration is below 25% of the lower explosive limit when thermally decomposing 1kg/hr of
polythene at 450°C.
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