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Ultrasonic Testing in Pipe Extrusion

Foreword from the Author

This On-Line guide book is a HTML edition of seminars and publications[References] from the author Rolf Diederichs. This hand book should give newcomers to the extrusion market help with decisions, or making for current user a further knowledge base for this technology. There are, even for Ultrasonic NDT users, some useful reading.

The state of the art revued here, relates to [References] the years 1991 -1992. Some of the guide books´ content were at that time in their early stage , or just announced. This technology gained during the last years, more and more industrial standards and it is still today very topical. Nevertheless the author will, after some other HTML publications, update this edition.

Copyright is for Internet and other electronic media always a debatable issue. It is acceptable for readers to make a personal copy . But for any further copies or commercial use, the copyright law is relevant.
I welcome your suggestions now here via mail. ©copyright Rolf Diederichs 13. Dec 1995

Contents |Go Deutsch|


Ultrasonic technology was for over 40 years employed in the steel industry, initially with flaw detection and later joined by wall thickness measurement.

For the past 15 years the plastics industry has used ultrasonic testing in the field of wall thickness measurement of pipe extrusions.

Quality considerations and material savings serve as arguments for investment in and protection against the increasingly important aspect of product liability. Also, Automation increasingly is being used in order to facilitate the use of data to recalculate the production costs of individual products and optimize the entire plant from this.

- Material Saving
- Automation
- Quality Control

In the last few years, considerable efforts were made to utilize ultrasonic wall thickness measuring systems in the pipe extrusion. This ultimately was demonstrated by a multitude of key patents.

In practice, the following points are important:

Where: at which point in the extrusion line can the ultrasonic technology be utilized advantageously? Is it better to measure near the die or away from the die, where is it worthwhile to use which control, etc.?

How: Here various measuring principles will be compared e.g. using fixed and reversing transducers through a water path ; or direct contact, with manual or automatic calibration, etc. will be compared.

The goal of this tutorial is to present an introduction to ultrasonics but with a concentration on the application. This information gives extruding company personnel practical guidelines for discussions with distributors of ultrasonic technology.

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Rolf Diederichs 13.Dec 1995, rd@ndt.net

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