11
09 2025
Melt Pump Pressure Sensor Frequently Asked Questions
Should pressure or flow be controlled?
For most lines, pump inlet pressure control provides indirect but reliable flow control. Direct mass flow meters are expensive and difficult to maintain at high temperatures.
How do I choose the sensor range?
Choose a full scale (FS) 60–70% above your normal operating pressure. For example, 0–250 bar is a good choice for a typical 150 bar.
How long does PID tuning take?
With appropriate initial values and autotuning, it is possible to achieve stable tuning in a single shift. (This varies depending on the thermal inertia of the line.)
What happens when the recycled material content increases?
Viscosity fluctuation increases; slightly extending the I-time in the PID and increasing the PV filter are beneficial.
Common Errors and Solutions
Incorrect sensor location (pump outlet): Control is ineffective because the fluctuation at the inlet is not read. → Move the sensor to the pump inlet.
Excessive P gain: Output oscillates → Reduce P, add a PV filter.
Integral wind-up (I wind-up): Stacking at start/stops → Use anti-windup or I limit.
Analog scaling error: 0–10 V ↔ 0–100% mapping is incorrect → The same range must be defined in the drive and controller.