7.0 Repairs and Replacements
7.6
Panel Element Replacement
See section 7.2 - wearing a face mask is required.
The chambers have two side-mounted refractory panels in which coiled heating
elements are inserted and one unheated hearth slab.
Disconnect the furnace from the electrical supply and remove the furnace back panel.
Make a written plan showing ALL the element and thermocouple connections. It is
important to make this plan for each individual furnace.
Disconnect all the element wire tails and thermocouple cables from their terminal
blocks. Straighten all the element tails.
Note that these become brittle with use.
Unscrew the screws fixing the metal back piece to the insulation assembly, and carefully
remove it, complete with thermocouple(s) and sheath(s).
Withdraw the back insulation piece. Handle with care. Observe the warning on handling
of ceramic fibre insulation.
Withdraw the old element(s), and insert the new. Note that in some models the ceramic
element carriers are in two parts: handle with care.
Replace the back insulation piece and metal piece, together with the thermocouple(s)
and sheath(s).
As necessary, shorten the element tails by clipping to the required length. Remake all
the thermocouple and element connections according to the individual plan.
Refit the back panel and operate the furnace for 30 minutes at 800 °C without
interruption to ensure complete burn-off of any organic binders. Some smoke may be
observed during this process, which should be carried out in a well ventilated area.
Check that the furnace is controlling properly to rule out the possibility that the previous
element failed because of a fault elsewhere in the control circuit.
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