The walls of plastic fuel tanks consists of 5 or more layers. One of which, is being used to reduce HC-emission. This is often done with a thin Ethylene vinyl alcohol (EVOH) layer. Measuring the thickness of this layer is a crucial factor of fuel tank quality assurance.
A common, but time consuming and destructive method to measure layer thickness is to cut out samples from a fuel tank wall. The samples have to be prepared for measurement by microscope.
The ultrasonic measurement of thin layers (<100µm) requires the use high frequencies, but plastic (HDPE) has a very high attenuation for high frequencies. There is no signal left after travelling thru a 8mm thick PFT wall.
Our ultrasonic measurement system is an invaluable tool for EVOH layer thickness gauging in PFT. The device is able to measure EVOH layers 40-50 µm
Total wall thickness: 2-8mm
EVOH-thickness: 50-250µm
Accuracy: +/-10µm at 3% EVOH layer
