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 Bake-Out Procedure for Multiple Zone Furnaces

The furnace contains carefully selected insulation to permit the best possible operation.  This insulation inherently contains moisture that must be slowly and completely removed before the furnace can be fully utilized.  During this drying period, a small quantity of smoke and vapors from the binders in the embedding cement will also be emitted.  The smoke will have a bad odor, so provide adequate ventilation. 

Please inspect the furnace prior to the bake-out procedure.  Please be sure that the furnace core is empty, that nothing is inside of it (ie. no papers, office supplies, tools etc).  Please be sure that nothing is on the exterior of the furnace as well.

Please follow the recommended procedure to properly dry out the furnace insulation for maximum operating success.  

1. Position the furnace vertically or to a position not lower than 30 degrees to the horizontal.

2. Leave the furnace ends open.

3. Vent the smoke outside through the use of a hood or exhaust collector.

4. Make certain that the core is empty.

5. Check the furnace power leads for possible shorts.

6. On the first firing, the power should be applied to every other zone, never to two adjoining zones at the same time.  The zones that are not fired should be completely disconnected from their power source.  It is recommended that in a three zone furnace, that the middle zone (zone 2) be fired or baked-out first.  Then, upon completion of zone 2 bake out procedure, that zones 1 and 3 can be baked out together.

7. Raise the temperature of the zones being fired to a minimum of 1000° C in four steps:

200° C for two (2) hours

400°C for two (2) hours

800°C for one (1) hour

1000°C for one (1) hour  

8.      After this bake-out has been completed, turn off the zones and completely disconnect as in Step 6.  The rest of the zones may now be connected and baked-out following the same procedures.

After the initial drying out run, all zones should be connected and the furnace should be run approximately 10°C - 40°C above the normal operating temperature, without exceeding the rated temperature, to fully stabilize the furnace.  Under no circumstances should the rated temperature of the furnace be exceeded.

WARNING: Multi-zone furnaces – SERIOUS DAMAGE may result if steps 6-8 are not followed when baking out multi-zone furnaces.

WARNING: Due to the possibility of combustible gases being given off by the refractory cement binders as the furnace is heated, Mellen recommends operating the furnace in a tilted or vertical position prevent local hot spots an possible damage to the heating elements or element.  Both ends of the bore should be open and the bore empty.  After the initial run, the furnace can be operated normally.

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