Carbolite TZF Series - Manual (Page 9)

1700-1800° Tube
MF32 - 3.25
9
Customers are advised periodically to check the thermocouple output, either by a calibration test,
or by comparing the output with a new reference thermocouple which has been subjected to high
temperatures for a minimum length of time.
Failure to check the thermocouple may result in overheating of the work and the furnace.
(2) The thermocouples fitted to these models give very low outputs below about 600°C, and do not
give accurate readings at low temperatures. The furnaces are not intended to be operated below
600°C.
4.0 M AINTENANCE
4.1 Routine Maintenance
No routine maintenance is required. The outer surfaces may be cleaned with a damp cloth. Do not
allow water to enter the interior of the case, tube or control box. Do not clean with organic
solvents.
4.2 Calibration
After prolonged use the controller and/or thermocouple could require recalibration; see the
warning about thermocouples in section 3.8. This would be important for processes which require
accurate temperature readings or which use the furnace close to its maximum temperature. A quick
check using an independent thermocouple and temperature indicator should be made from time to
time to determine whether full calibration is required. Carbolite can supply these items.
Depending on the controller, the controller manual may contain calibration instructions.
4.3 After Sales Service
Carbolite’s service division (Carbolite Engineering Services) has a team of Service Engineers
capable of repair, calibration and preventive maintenance of furnace and oven products at our
customers’ premises throughout the world. We also sell spares by mail order. A telephone call or
fax often enables a fault to be diagnosed and the necessary spare part despatched.
Each furnace has its own record card at Carbolite. In all correspondence please quote the serial
number, model type and voltage given on the rating label of the furnace. The serial number and
model type are also given on the front of this booklet when supplied with a furnace.
To contact Carbolite Engineering Services or Carbolite see the back page of this manual.
4.4 Recommended Spares Kits
Carbolite can supply individual spares, or a kit of the items most likely to be required. Ordering a
kit in advance can save time in the event of a breakdown. Each kit comprises one thermocouple,
one sheath, one power thyristor, and a set of elements, clips and braids. It is advisable also to
obtain element clamps and insulators (not included in kit).
When ordering spares please quote the model details as requested above.
4.5 Power Adjustment (Controller)
The furnace controller incorporates a power limit parameter OP.Hi which is usually inaccessible to
the operator.
Occasionally the power limit is set to zero to permit demonstration of the controls without the
heating elements taking power. In this case the power limit is accessible to the operator and may
be reset to its standard value of 100.
4.6 Power Adjustment (Thryristor)
The current-limiting thyristor stacks which control power to the elements are fitted with an
adjustable resistor which is factory set to limit the maximum current supplied. In the event of a
change of supply voltage, or the fitting of a new thyristor, further adjustment may be required.