M970-07/04
PAGE 17
Monitor the furnace temperature using the standard reference probe on the measuring
instrument or plot as a graph using PC soft-ware. When final temperature stabilization is
re ached the end zones should be in control with their control lamps blinking to indicate
an average control power input to the furnace end zones.
Checking horizontal uniformity
The temperature uniformity from end to end of the furnace will vary depending upon the
end zone losses. These vary with the temperature value, being much higher at 600 to
1200 deg.C. The total losses and end zone “temperature droop” will also be dependant
on the end zone insulation and its packing density used, together with the size, type and
number of probes inserted.
To check and adjust/trim the furnace end zone differential “offsets”, insert a long TC
probe into the centre hole of the equalization block in furnace. It is assumed that the
block has been mounted centrally between the furnace ends. While recording this
probe in the centre position, slowly re-position it at l in. intervals and monitor the
temperature change. Leave the probe at each position for approximately 5 mins.
dependant on probe response time to achieve thermal equilibrium. The temperature
profile over +/- 4 ins. from the centre of the block can be monitored. The end zone
controller up/down keys can be adjusted to obtain the best uniformity.
The reference and probes under calibration can be scanned and monitored by an
attached DVM/scanner or using the TTI7 digital thermometer / scanner system. Refer to
Section 16 for automatic calibration and data logging under computer control.
