OM-222166 Page 32
Maximum Temperature Message Screen
Cannot enter Run mode
Programmed temperature settings
exceed air cooled limits
(400
_
F, 204
_
C)
7-5-1-4. PWHT Operation
When a PWHT cycle is started, you may monitor where you are at in the cycle by selecting the Status Screen. From there you can determine what mode
you are in, what the heat controller’s current calculated target temperature is, and see the Soak Timer Countdown.
When using a single TC in the control loop, it is in control of the entire cycle. When using 2 - 4 control TCs, the ProHeat 35’s heat control has the following
characteristics:
•
When ramping up from the Ramp temperature to the Soak temperature, the TC with the highest temperature is the TC in control.
•
In many applications, the temperature of all the control TCs stay close together throughout the entire cycle, within the the programmed tolerance
band (default is +/- 25
°
F) of the set point. In these typical cases, the unit continues from the Ramp cycle into the Soak cycle, and the Soak countdown
timer starts.
When at the Soak temperature set point, all control TC temperatures must be within the tolerance band before the Soak countdown timer will start. If
all TCs are not within tolerance, heating continues until the hottest TC reaches the set point plus the tolerance band. The unit does not allow output
above the set point plus the tolerance band. If all temperatures are not within the tolerance band, you have three options :
1.
Allow time for the heat to conduct around and through the material. This may allow the area with the coolest TC to heat up above the minimum
(set point − tolerance) allowing the Soak cycle to continue.
2.
Manipulate the coil over the hot area, allowing that area to cool down. To accomplish this, you must stop the cycle, spread coil turns apart,
remove coil turns, or pull the coil away (decoupling the coil) only over the area where the hot control TC is located. As a result, the output power will
increase slightly allowing the cooler areas to heat up.
3.
Change the tolerance band. To accomplish this, stop the cycle, enter the Setup screen and increase the tolerance setting. Resume the cycle.
Certain codes such as ASME B31.1 and B31.3, do not allow tolerance settings over +/- 25
°
F, so be sure to check the code, or check with your
engineers to see if this is allowed.
•
When ramping down from the Soak temperature to the Ramp temperature, the TC with lowest temperature is the TC in control.
•
If the part cannot be heated at the requested rate (i.e. because of part mass, coil setup, etc.) the target temp displayed by the heat control will never
exceed a 10
°
F difference from the control TC.
7-5-1-5. Custom Program
In Custom Program, the operator can create a custom program with multiple steps or nonsymmetrical heat treat programs where the heating and
cooling rates and temperatures are different. When this process is selected, the following screen appears on the display:
.
This is the screen for initial use of the system. Subsequent use of custom program will revert to the last program used.
Mode.......: Custom Program
Segment....: 1
Type.......: End
Control TC.: 1
Custom Program Screen
The default position of the cursor is next to Segment. Press the Increase
or Decrease
button to increase or decrease the seg-
ment number, unless the segment type is End. In this case, the segment number will advance to segment 1.