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Chapter 4
Ramp-Hold
Definition of a Segment
Ramp-Hold fires in segments. Every segment must have
a targettemperature anda heatingrate to reachthat temper
-
ature. Shown in diagram A is a segment with a temperature
of 750°.
Rate is figured in degrees per hour. In Diagram A above,
the temperature takes two hours to reach 750°. The rate is
750 ÷2 = 375.
Diagram B, below, shows three rates. A rate of 1000° will
reach 1000° in 1 hour. A rate of 500° will reach 1000° in 2
hours. A rate of 333° will reach 1000° in 3 hours.
A segment, which is a target temperature and a rate of
heating to reachthat temperature, canalso have a hold.Hold
maintains the target temperature for the length of time you
specify. (Diagram C, above.)
A segment has two parts:
■
Ramp: where the temperature changes
■
Hold: where the temperature remains the same
A segment can have only one ramp and only one hold.
Therefore, if you need more than one hold, you will have to
add additional segments to the firing. Firing to a tempera-
tureat asingle ratewouldneed onlyone segment.Reasonsto
add more segments:
■
To change the heating rate
■
To add a hold somewhere below the shut-off tempera-
ture
■
To change the temperature direction. Example: to con
-
trol the cooling rate.
Diagram D, below, shows a 3 segment firing. Two seg
-
ments were used on the way up in temperature. Another
segment was added for controlled cooling.
12
Diagram A: a single segment.
Diagram C: a single segment with hold. The two parts of a segment are
the ramp and the hold. Not all segments have a hold, but they all have a
ramp.
Diagram D: a 3 segment firing. Only 2 segments have a hold.
DiagramB:Rateisdegreesperhour.This diagramshows3rates.Di
-
vide the target temperature by the number of hours it took to reach that
temperature.