6.5
Operator Safety
This product incorporates a safety switch which interrupts the heating
element circuit when the furnace is opened. This prevents the operator
touching a live heating element and also prevents the product from
heating up if the furnace is left open. The operation of this switch should
be checked periodically.
Depending on use, the surfaces in the working chamber and the
chamber load may still be very hot after the appliance is switched off.
Touching these surfaces may cause burns. Use suitable personal
protective equipment or wait until the appliance cools down to ambient
temperature.
Before removing a hot object from the product, make sure there is a safe place to put it
down. If necessary use tongs, face masks and heat resistant gloves. Heat resistant
clothing and face protection can guard against the effects of radiated heat when the
furnace is open.
When the product is opened during operation there is considerable radiated heat. Do
not keep any flammable objects near the product, nor objects which could be damaged
by radiated heat.
6.6
Notes on Temperature Control
This product is designed for heating and cooling at controlled rates. The heating and
cooling rates can be set in the temperature programmer. The programmer enables the
furnace to heat or cool at slower rates as desired and variable "hold" (dwell) periods
can be programmed as required.
The programmer is used in conjunction with a phase angle thyristor power controller,
which incorporates a current limit potentiometer pre-set by Carbolite Gero, but which
will require adjustment in the event of change of supply voltage.
The elements are connected in series across the low voltage output of a transformer
housed in the furnace case. Molybdenum disilicide elements do not age, if an element
fails it is not necessary to replace the complete set.
6.7
Insulation Cracking
In these furnaces the insulation material is susceptible to surface cracking as a result of
high temperature cycling; this is a normal occurrence and such cracking is not
detrimental to the performance of the furnace.
6.8
Thermocouple Warnings
(1) The output from 1700-1800 °C thermocouples when used regularly at temperatures
greater than 1650 °C can deteriorate and decrease with age faster than if used at
temperatures below 1650 °C; this will cause the furnace to operate at temperatures
higher than indicated.
45
6.0 Operation
