Span Your Valves
Chapter 9
9-18
6.
If the observed pressure HPS16 for pack and HPS33 for hold are still
not within 20% of setpoints HPC16 and HPC33, your pressure valve
is not linear over the desired range of operation. Correct for a
non-linear valve by adjusting the Selected Pressure Valve, Output for
Minimum: PKC43 for pack or HDC43 for hold as follows:
If actuals are at least 20%: And Your Selected
Valve is:
Then change PKC43 or HDC43
(N44:159 or N44:219) as follows
Less than setpoints
Direct Acting
Increase in 5% steps
Reverse Acting
Decrease in 5% steps
Greater than setpoints
Direct Acting
Decrease in 5% steps
Reverse Acting
Increase in 5% steps
To do this, change PKC43 and/or HDC43, download PKC and HDC
followed by HPC with bits B21/9, 10, 11, and repeat steps 3 and 4.
What You Have Accomplished
The open-loop tuning procedure you just completed has defined the:
range of ram (screw) backpressure during plastication
end-of-range maximum and minimum signal levels for linear control of
the plastication pressure valve in open-loop control
For this
range limit
When trying to obtain
the pressure in:
The QDC module drives the selected
pressure valve to % output signal in:
Minimum
PKC41 or HDC41
PKC43 or HDC43
Maximum
PKC42 or HDC42
PKC44 or HDC44
Now for all open-loop pack or hold pressure profiles, the QDC module
assumes a linear relationship between ram pressure and signal outputs.