PRODUCTION MANAGERS | Change Pressure Transducers / Transmitters for Color or Material Changes?
- Bob
- Aug 30
- 2 min read
We get asked this often as part of a larger best practice type question. Here are some different factors to consider when faced with scheduled replacement of critical melt pressure sensors.
Color Changes (Plastics or Food Dyes)
Pigments and colorants don’t typically harm the diaphragm.
Risk: some pigments are abrasive (e.g., titanium dioxide in white masterbatch), which can cause erosion of the diaphragm surface over long use.
Action:
No replacement needed.
Clean diaphragm face during purge/changeover.
Inspect for wear if abrasive materials are run frequently.
Different Polymer Types (Plastics)
Some polymers process at different melt temperatures and viscosities.
Risks:
Higher processing temps may exceed the sensor’s rated temp → accelerated drift/failure.
Materials with fillers (glass fiber, mineral) can abrade or pit the diaphragm.
Residues from one resin can carbonize if not cleaned before running a new resin.
Action:
No automatic replacement.
Ensure the sensor’s pressure and temperature rating covers the new resin.
Always purge/clean the port to avoid residue build-up.
Food Applications
Different products (e.g., syrups, purees, starches) may have sticky residues that harden.
Risk: cross-contamination if not fully cleaned.
Action:
Flush diaphragm sensors are preferred.
Transducer is cleaned and sanitized but not replaced unless damaged.
When Replacement IS Needed
Replace the transducer if......
The new material runs at higher pressure or temperature than sensor’s rating.
The diaphragm is pitted, dented, or scratched during cleaning.
Sensor has drifted too far and calibration no longer holds.
In food: when hygienic compliance rules (FDA, EHEDG) mandate replacement after damage or at end of validated lifespan.
PLANNING TIPS :You do not replace melt pressure transducers just for material or color changeovers. Instead, you clean, inspect, and recalibrate. Only replace if the diaphragm is damaged, the sensor is out of spec, or the new material exceeds the sensor’s ratings. Of course NNS always recommends consulting your in plant process engineers.
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