A Multi-probe concept is necessary to meet the demands of an
ultrasonic weld test during pipeline assembly. The weld must be
tested completely during one turn around the pipe circumference.
This article describes an equipment concept that worked satisfactorily in
the field.
The data evaluation and post processing must work error-free under certain
conditions like changes in test object dimensions.
Correct separation of phantom and flaw echoes in
the root of the weld presents a special challenge due to nonuniformly
performed manual welding.
The solutions are introduced.
Common pipeline materials contain anisotropic elements which have great
influence on sound propagation and this must be taken into consideration.
The differences in this method vs. manually performed ultrasonic testing,
based on recent
specifications, are described with respective test results.
Pipeline conditions
In order to develop a good probe concept it is essential to look at the behavior of the materials as well as different shapes of welds. It's very clearly shown that the material behaves differently than that of the reference block e.g. K 1. The pipes are usually manufactured by use of thermo-formed steel plates and exhibit ultrasonically anisotropic behavior. Because a good understanding of propagation is essential, we have performed a comprehensive study together with Krautkraemer which we summarize here:- Shear waves velocities differ significantly between the longitudinal and
transverse
direction
(e.g. long.: 3.385 m/s - trans: 3.150 m/s).
- The shear wave velocity changes with the angle of incidence
- The angle of propagation is influenced by the frequency
- The maximum sound energy does lie not on the same axis as the sound beam.
- Shear waves can only be excited up to 67°
- Snell's law can not be applied for calculation of the sound propagation
- The influence on the velocity, angle of propagation and the sound beam
shape increased in proportion to the distance of
the angle of incidence from the 45 °.
- The same material from different suppliers shows different ultrasound behavior as well as a different wall thickness from the same suppliers.
That makes clear that the measurement of sound propagation on calibration
blocks are not adaptable to pipeline materials.
In international publications the ultrasound behavior is oversimplified
according to Snell's law.
Defined focusing is determined on homogeneous calibration
blocks and a 72° angle of incidence is reported.
A test concept and the ultrasound propagation must be tested on the
original material.
Figures of the German full text:
 Fig 1: Positon of the falt bottom holes |
| Table 1
US - manaul test adjusted with AVG - FBH 1.0 Compared with FBH 1.0 mm in X70 test stripe Reflector No. | Echo height (dB) to AVG | MWB 45-4 Echo height (dB) to AVG | MWB 60-4 1
| - 8
| - 4
| 2
| - 8
| - 3
| 3
| - 12
| - 3
| 4
| - 12
| - 3
| 5
| - 7
| - 6
| 6
| - 10
| -3
| 7
| - 10
| - 4
| 8
| - 9
| - 3
| 9
| - 9
| - 3
| 10
| - 8
| - 3
| 11
| - 8
| - 3
| 12
| - 10
| - 4
| 13
| 0
| - 4
| 14
| - 3
| - 5
| |
 Abb 2: Schema of UT - MIPA - WELDSCANNER |
 Abb 3: 3 dB Dynamic for H 5 M probe on 1mm FBH |