Keison CARBOLITE AAF 11/18, Installation, Operation & Maintenance Instructions Manual

AAF, OAF, GSM, VMF 

Slab Element Replacement (OAF 11/2) 

See section 5.2 - wearing a face mask is recommended. 

The twin chamber contains two slab elements which form the heated floors of the upper and lower 
sections. The elements are made of refractory cement in which coiled heating wire s embedded. 

Disconnect the furnace from the electrical supply. Remove the furnace back panel and make a 
simple drawing of how the wires are connected to the elements. 

Release the screws which secure the element terminal blocks on the faulty elements. (Element tails 
become brittle with use, so care must be taken during removal, unless you intend to replace them 
all.) 

Open the furnace door. With a hacksaw blade cut grooves in the front brick sides sufficient only to 
enable the elements to slide out forwards. Remove the elements and tidy these grooves with a file. 

Check the condition of the insulation adjacent to the faulty element(s). Replace the insulation if it 
is excessively cracked of has radically changed colour or texture. 

Slide in the new element(s). Guide the tails through the existing holes in the insulation and re-
connect the element terminal blocks. 

Cut off any excess tail wire, replace the back panel and reconnect the electrical supply. 

Switch the furnace ON and heat to 900°C without interruption, then soak for 1 hour. 

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. 

5.9  VMF 10/6 Element Replacement 

See section 5.2 - wearing a face mask is recommended. 

The heating elements are vacuum formed modules; they are fragile, so spare elements are supplied 
complete in an insulation box to avoid damage. 

Disconnect the furnace, remove the back panel, make a plan of all the internal connections to the 
back of the heating chamber and disconnect. Remove the thermocouple(s) and support tube(s). 

Using a socket spanner undo the four bolts that fasten the insulation box. These are located under 
the insulation box in the two cross supports. 

Remove the insulation box by carefully sliding it out through the back of the furnace case. 

Carefully slide in the new insulation box, and fasten the four bolts. DO NOT support the element 
by putting your hand inside the chamber – the element is fragile. 

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 the previous element 
failed because of a fault elsewhere in the control circuit. 

5.10 

12 

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