| This range comprises the following
models: RHF 1700°C with chamber capacities of 3.4, 10 and 25 litres;
HTF 1800°C with chamber capacities of 3.4, 14.5 and 27 litres and
the HTC 1800°C with a chamber capacity of 7.7 litres.
All models (excluding the HTC) feature lightweight
fibre insulation, which allows rapid heating and cooling, but requires
more care when loading to avoid accidental or abrasion damage. The HTC
has a hard refractory brick lined chamber which provides a durable work
area and excellent abrasion resistance, but reduces the heating and
cooling rates.
Heating in all models is provided by molybdenum disilicide
elements, which are known as Kanthal Super Elements. They comprise molybdenum
disilicide (MoSi2) and a component that which forms a dense
protecting layer of glass around it at working temperature. This feature
is the key to the superior properties of the Kanthal Super. The elements
can be used continuously or intermittently and can either be used in
air or with the usual protective gases. As Kanthal Super Elements do
not increase in resistance with use, there is no need for a voltage
reserve. Should an element fail it may be replaced without affecting
other elements in the same circuit. Long life combined with ease of
replacement contributes to a high degree of usage and low maintenance
costs. The 'U' shaped elements, which are mounted on either side of
the chamber (the HTF 18/27 also has elements located in the back of
the chamber), are controlled using a sophisticated control circuit to
meet with European EMC legislation.
The upward motion of the door keeps the hot face away
from the operator, which is critical when working at such high temperatures,
and allows easy and full access to the chamber. The RHF 3 and 10 litre
capacity models are offered with a choice of either manually or electrically
operated door, whereas other models are available with an electrically
operated door only; the HTF 18/27 model offers a manual door only. The
gentle closure of the electric door protects both the heating elements
and delicate loads from possible impact damage.
A cool outer case temperature is maintained by electric
fans which accelerate the movement of air in the gap between the insulation
and the outer case.
Adjustable overtemperature protection is fitted as
standard. An additional thermocouple and controller are linked to a
contactor. The system can be set to protect the furnace or adjusted
to a lower temperature to protect a valuable furnace load. 
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