Why Melt Pressure Transducers Fail in Glass-Filled Processes

Our Tech Squad gets this call or email regularly, so want to share some thoughts!

Glass-filled polymers are extremely common in modern plastics processing. Materials such as 30–40% glass-filled nylon, polypropylene, and engineering resins provide superior strength and dimensional stability.

Unfortunately, they also create one of the harshest environments for melt pressure transducers.

Many extrusion plants experience frequent sensor failures when running filled materials. Understanding why this happens can dramatically extend sensor life and reduce downtime.

The Main Reason: Abrasive Fillers

Glass fibers act like microscopic cutting tools as they pass through the extruder.

These fibers continuously impact the sensor diaphragm, slowly wearing down the metal surface.

Over time this causes:

• Surface erosion

• Signal drift

• Sensitivity loss

• Eventually complete failure

Higher glass content makes the problem worse.

Typical wear environments include:

• 30–40% glass filled nylon

• Glass filled polypropylene

• Mineral filled engineering plastics

• Compounding operations

The Hidden Problem: Sensor Installation Depth <= IMPORTANT / PLEASE READ!!

Many sensor failures in filled materials are not caused by abrasion alone.

Another common issue is sensor setback inside the barrel.

If the tip of the transducer is recessed too far from the melt flow, polymer can accumulate and cool in the pocket. When the line heats and cools repeatedly, this hardened material can apply uneven stress to the diaphragm.

In some cases, this stress can actually crack the diaphragm face.

Temperature Cycling Accelerates Failure

Extrusion lines processing filled materials often run at temperatures between 500°F and 700°F.

Repeated heating and cooling cycles cause:

• Metal fatigue

• Diaphragm stress

• Seal degradation

Combined with abrasive fillers, this dramatically reduces sensor lifespan.

How Plants Extend Sensor Life

Extrusion engineers often use several strategies to increase sensor durability:

• Flush mounting sensors with the barrel wall

• Ensuring proper installation torque

• Selecting high-strength diaphragm materials**

• Avoiding recessed installation pockets (An often unknown killer!!)

• Performing regular calibration checks

Even small installation changes can significantly extend sensor life.

Glass-filled plastics create one of the most demanding environments for melt pressure measurement. Understanding how abrasion, installation geometry, and temperature cycling interact can prevent unnecessary sensor failures.

Many plants assume frequent failures are unavoidable, but in reality proper installation and sensor selection can dramatically improve reliability.

Call or email today to talk!

TechSupport@NoNonSensors.com