Carbolite CFM Series - Manual (Page 7)

CFM
MF10 - 3.08
7
4.0 M AINTENANCE
4.1 General Maintenance
No routine maintenance is required other than the occasional replacement of consumable items.
The furnace outer surface may be cleaned with a damp cloth. Do not allow water to enter the
interior of the case or chamber. Do not clean with organic solvents.
4.2 Calibration
After prolonged use the controller and/or thermocouple could require recalibration. 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 solid state relay, one heating element or set of elements. For 1400°C models the kits also
include element clips and braids. Individual spares are also available.
When ordering spares please quote the model details as requested above.
4.5 Power Limit
In the 1400°C models the furnace control system incorporates electronic power limiting. Power is
supplied to the elements in bursts of about 1/3rd second duration. This prevents overheating of the
elements. The power limit is programmed into the furnace controller and may be calculated as a
percentage as follows:
powerlimit = (100 x targetpower x ohms) / volts
2
where targetpower is the wattage given on the furnace rating label
ohms is the overall resistance of the combined element circuits (see example)
volts is the voltage across each element circuit (e.g. 240 for a 415/240V supply)
example:
1-phase furnace with 4 elements of 3.6 ohms each in series, running on
220V, with a target power of 2250W:
ohms = 3.6 x 4 = 14.4
powerlimit = (100 x 2250 x 14.4) / (220 x 220) = 67%
A table of power limit settings is given in section 7.6. These are the settings for the furnace with
new elements as supplied.