MTF 9/15
R
EPAIRS
& R
EPLACEMENTS
6.1 Safety Warning – Disconnection from Supply
Always ensure that the furnace is disconnected from the supply before repair work
is carried out.
6.2
Safety Warning - Refractory Fibrous Insulation
This furnace contains refractory fibres in its thermal insulation. These materials may
be in the form of fibre blanket or felt, vacuum formed board or shapes, mineral wool
slab or loose fill fibre.
Normal use of the furnace does not result in any significant level of airborne dust from these
materials, but much higher levels may be encountered during maintenance or repair.
Whilst there is no evidence of any long term health hazards, we strongly recommend that safety
precautions are taken whenever the materials are handled.
Exposure to dust from fibre which has been used at high temperatures may cause
respiratory disease.
When handling fibre always use an approved mask, eye protection, gloves and long
sleeved clothing.
Avoid breaking up waste material. Dispose of waste fibre in sealed containers.
After handling rinse exposed skin with water before washing gently with soap (not
detergent). Wash work clothing separately.
Before commencing any major repairs we recommend reference to the European Ceramic Fibre
Industry Association Bulletin No. 11 and the UK Health and Safety Executive Guidance Note
EH46.
We can provide further information on request. Alternatively our service division can quote for
any repairs to be carried out at your premises or ours.
6.3
Temperature Controller Replacement
Ease apart the two lugs at the side; grip the instrument and withdraw it from its sleeve; push in the
replacement.
6.4 Thermocouple Replacement
Disconnect the furnace from the supply; disconnect the thermocouple from the controller, noting
the connections.
Release the screw which secures the thermocouple sheath.
Reassemble with a new thermocouple, ensuring that the new one is in good contact with the tube
wall.
Ensure that the negative side of the thermocouple (marked blue) is connected to the negative
terminal of the controller.
6.5 Element Replacement
See section 6.2- wearing a face mask is recommended.
The furnace is heated by resistance wire wound onto a small ceramic tube. This is centred in a
cylinder of insulation. The element is terminated by bringing the ends of the heating wire out
through grooves cut in the ends of the insulation cylinder. The wire is electrically insulated from
the foil, which covers the insulation, by ceramic beads and by discs of glass fibre cloth which
cover the ends of the insulation cylinders.
To replace the element it is necessary to cut the binding which attaches the element to the chassis.
Replacement binding is supplied with the spare element.
MF09
11
