Carbolite VMF Series - Manual (Page 10)

AAF, GSM, VMF
10 MF06 – 3.32
Switch the furnace ON and heat to 900°C without interruption, and then soak for 1 hour. 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 previous element
failed because of a fault in the control circuit.
5.7 Panel Element Replacement (AAF 11/18 and 12/18)
See section 5.2 - wearing a face mask is recommended.
The chambers have two side-mounted refractory panels in which coiled heating elements are
inserted, normally out of sight behind silicon carbide chamber walls.
Disconnect the furnace from the 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 from the inner chamber and withdraw this part
backwards complete with thermocouple(s) and sheath(s).
Withdraw the back insulation piece. Handle with care. Observe the warning on handling of
ceramic fibrous insulation – section 5.2.
Remove the Silicon Carbide chamber side walls, then withdraw the old element(s), and insert the
new. Note that the ceramic element carriers are in two pieces, front and back: take care when
handling them.
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 length.
Remake all the thermocouple and element connections according to the individual plan.
Refit the back panel and run 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 previous element
failed because of a fault elsewhere in the control circuit.
N
AAF 11/18 element connection example
(1-phase 200-240V)
L
N
L
L
N
link
terminal
block