wall thickness equation :These reflected pulses return to the transducer where they are recorded. The transmission time of the pulse, counted from where it enters the measured body to where it returns through the same spot equals two times the wall thickness of the measured body. Multiplication of this transit time by the material sound speed properties, gives the value of the wall thickness.
The mechanic coupling fixtures, which direct the transducer on the test specimen, are different. According to the application environment 3 different methods can be applied.
Direct-Coupling is applied in large pipe dimension. Here a good sound throughput is achieved. This method is therefor applied when other coupling methods do not succeed.
Waterpath-Coupling is the most widley applied method. It is applied in a wide dimension range.
Immersion-Coupling is general recommended with small pipe dimensions where here are non contact and non force measurement is necessary.
Rolf Diederichs 18.Dec.1995, email@example.com