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Heatpipe Furnace Models 17702W, 17702P, 17702S (13
–
07/20)
METHOD OF OPERATION
1.
By adjusting set-point to a few degrees above the appropriate melting point, the cell (zinc,
aluminium or silver) is melted in an essentially temperature gradient free potassium-filled heat-pipe.
When melting is complete, the heat-pipe temperature is readjusted to a level 0.5°C below the freeze
temperature of the cell. When this set-point has been reached a cold rod is introduced into the re-
entrant tube of the cell to initiate the freeze, giving a plateau that can be maintained for between 12
and 24 hours.
2.
The thermometers are removed from their storage rack and placed in the pre-conditioning furnace.
The furnace is slowly heated to 400°C (if the cell is zinc), 650°C (for aluminium) or 900°C (for
silver).
During conditioning, thermometers are protected from contamination by a slow air flux around them.
CAUTION:
it is essential, when thermometers are inserted into furnaces, to keep their heads cool.
This can be accomplished by blowing air, at ambient temperature, across them by means of a free-
standing fan.
3.
Thermometers are transferred individually to the cell for 20 to 30 minutes, for calibration, and then
returned to the post-conditioning furnace.
4.
When all the thermometers have been calibrated, the post-annealing furnace is slowly cooled to
450°C after which they can safely be exposed to room temperature and, thereafter, measured at the
triple point of water.
Throughout the time the thermometers are above 450°C the temperature changes are slow enough
to prevent strain, and the slow flow of air prevents contamination at high temperatures.
