Carbolite CFM Series - Manual (Page 6)

CFM
6
MF10 - 3.08
3.3 General Operating Advice
Heating element life is shortened by use at temperatures close to maximum. Do not leave the
furnace at high temperature when not required. The maximum temperature is shown on the
furnace rating label and on the back page of this manual.
Lightweight ceramic fibre insulation can easily be marked by accidental contact. Some fine cracks
may be visible on the surface of the insulation, or may develop in the surface of the chamber due
to the progressive shrinkage of the insulation materials. Cracks are not usually detrimental to the
functioning or the safety of the furnace.
Switch off the Heater switch whenever loading or unloading the furnace - see the safety warning
below.
3.4 Tube Life
A work tube may be cracked if workpieces are inserted too
quickly or at temperatures below 900°C (when the tube is
more brittle). Large pieces should also be heated slowly to
ensure that large temperature differences do not arise.
Poor thermal contact should be encouraged between the
workpiece and the tube; crucibles or boats should be of low
thermal mass and should have feet to reduce the contact
with the tube.
Avoid metal directly touching the work tube - see the safety warning below.
3.5 Operator Safety
The ceramic materials used in furnace manufacture become electrically conductive to some extent
at high temperatures. DO NOT use any conductive tools within the work tube without isolating it.
The work tube is isolated when the Heater switch is OFF. This switch cuts both sides of the circuit
directly or, where the rated current exceeds 16 Amps, via a contactor.
3.6 Pressure
Work tubes are not able to accept high internal pressure. When gas seals or similar fittings are in
use, the gas pressure should be restricted to a maximum of 0.2 bar (3 psi). A pressure of about half
of that should normally be sufficient to achieve the desired flow rate. The customer must ensure
that the exhaust path from the tube is not blocked, so that excess pressure does not occur.