HIGH TEMPERATURE
FURNACE HANDBOOK
ISSUE 8 - 05/05
Page 10 of 37
A further safety device is provided in the furnace and is accessible by removing the top
panel and some fibre insulation. It comprises a gold wire (Potassium Heat Pipe only) in
series with the primary power circuit and is essentially in thermal contact with the furnace
core. Its function is to melt if both other control systems fail. This thermal fuse should not
be replaced after failure until the causative fault has been understood and corrected! The
terminal posts for fuse-connection are sited on the outer shell of the furnace assembly facing
the rear panel.
A section through the sealed type of metal freezing-point cell used in the furnace is shown in
Figure 1 and cell external dimensions are specified in Figure 2.
Figure 3 shows a section through the furnace (not to scale) together with the layout of the
controllers and power switch on the front panel.
The furnace is equipped with a thermometer pre-heating tube.
