Carbolite HTF Series - Manual (Page 10)

RHF & HTF
10
MF22 3.09
5.6 Element Installation & Replacement
Safety Warning – Molybdenum Disilicide elements.
The elements form a glazed surface when heated. Internal stresses can form
through heating and cooling which render the glaze fragile. The glaze can
sometimes splinter into a shower of sharp particles when handled. Always wear eye
protection when handling the elements.
Handle the heating elements with extreme care as they are very fragile. Also, avoid touching the
heating surface (the thin part of the element).
Replacement: Note the length of element above the fixing clamps before starting. Remove the
aluminium braids and clips using the clip tool provided with the furnace. Remove the clamp,
which has a screw fixing. Lift out the old element and any insulation pieces: handle the insulation
pieces with care as they are fragile.
Because of different furnace sizes and voltage configurations, there are a number of variations in
the detailed element support layout. The element diagrams show the main alternatives. Examine
and identify the loose components and the support system appropriate to your furnace. There are
also variations in the positions of the braids which connect the elements: the rule is that for single
phase all elements are in series; for 3-phase, each phase has 2 (or 3) elements in series.
Fit the insulation spacer or block to the element; if the element is suspended from strips or bars
above the chamber roof, fit also the element support block. Locate the clamp(s) over the element,
and tighten carefully. Lower the element into position, and connect the braids using finger pressure
or the clip tool provided.
Ensure that the element is correctly placed: the thin part of the element legs should be entirely
within the heating chamber; the element should not touch the bottom of the chamber. A guide to
the correct placement is given in the table below, using the measurement from the top of the clamp
to the top of the element.
Replacement: heat up the furnace to a moderate temperature and ensure that the furnace is
controlling properly, in case the previous element failure resulted from a fault in the control
system.
After installing new elements run the furnace at 1500°C for an hour. This creates a protective
glaze on the element surface.
Element Fitting Layouts