Carbolite STF Series - Manual (Page 6)

STF 14-16
6
LMF08 – 1.13
3.0 O PERATION
The instructions for operating the temperature controller are given in a separate manual.
If the furnace is fitted with a time switch, see also the supplementary manual LS03.
If cascade control is fitted, see the supplementary manual LS07.
3.1 Operating Cycle
The furnace is fitted with an instrument switch. The switch cuts off power to the control circuit.
There is also a heater switch which can be used to disconnect power to the elements.
Connect the furnace to the electrical supply.
Operate the instrument switch to activate the temperature controller. The controller becomes
illuminated and goes through a short test cycle.
Adjust the temperature controller (see controller manual).
Overtemperature option only. If the overtemperature controller has not yet been set as required, set
it and activate it according to the instructions in the appropriate manual.
Unless a time switch is fitted and is off, the furnace starts to heat up. The Heat light(s) glow
steadily at first and then flash as the furnace approaches the desired temperature or a program
setpoint.
Overtemperature option only. If the overtemperature trip operates then an indicator in the
overtemperature controller flashes, and the heating elements are isolated. Find and correct the
cause before resetting the overtemperature controller according the instructions supplied.
To turn the furnace off, set the Instrument switch to it’s off position; the controller display will go
blank. If the furnace is to be left off unattended, isolate it the electrical supply.
3.2 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.
Light weight 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.
3.3 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.
If a metal work tube is used, it must be earthed (grounded). Note that the furnace temperature
should be limited if a metal tube is used.
Ensure that there are no inflammable objects placed in such a way that the work tube could break
and fall on them.
Switch off the Heater switch whenever loading or unloading the furnace. The elements are isolated
when the Heater switch is OFF. This switch cuts both sides of the circuit directly or via a contactor
(a contactor is used in models where the rated current exceeds 16 Amps).
3.4 Tube Life
A ceramic work tube may crack if workpieces are inserted
too quickly or at temperatures below 900°C (when the
tube is more brittle). Large pieces should also be heated