Fast inspection with imaging phased array ultrasonic weld seam inspection
VOGT Ultrasonics and Meyer Werft replaced the radiographic butt inspection of all support structures in the are of the ship’s hull, for sheets made of normal and high-strength steel. Extensive barriers in the production halls and work interruptions at the bordering production islands which are mandatory for the radiographic inspection do now belong to the past thanks to Phased Array ultrasonic inspection.
Meyer Werft GmbH, in Papenburg- Germany, is one of the most progressive and innovative shipyards worldwide. Shipping companies and pleasure cruise tourists equally appreciate the comfortable and safe cruisers. Approximately 25.000 tons of steel are installed in just one modern Cruise Liner including numerous kinds of structural steels and sheets up to a thickness of 50 mm are being installed and joined by various welding processes such as inert gas- and laser-hybrid welding. Wherever welded seams play a key role for statics and safety of the ship, a precise quality control is necessary.
In the past welded seams were inspected on defect areas using conventional manual ultrasonic inspection techniques parallel to a radiographic inspection. In summer 2010 VOGT Ultrasonics and its customer Meyer Werft successfully implemented the manual weld seam inspection by using Phased Array ultrasonic contact technology according to common standards DIN EN 1712, 1713, 1714 and DIN EN 12062 – and herewith the basis for an inspection technology for a faster and more efficient quality control within the production process was established.
Since the end of 2010 the Phased Array inspection of butt for all support structures in the area of the ship’s hull, for sheets made of normal and high-strength steel with a wall thickness of 8 – 30 mm welds is approved by the three large classification societies Det Norske Veritas, Lloys’s Register EMEA and Germanischer Lloyd and has been approved to replace the radiographic inspection for the above mentioned applications. With this improvement, extensive barriers in the production halls and work interruptions at the bordering production islands which are mandatory for the radiographic inspection do now belong to the past thanks to Phased Array ultrasonic inspection. Inspection
Especially for weld seam inspection the advantages of the Phased Array technology offers new possibilities for the ultrasonic inspector. Via sector scan a variety of inspection angles can be covered by only one transducer and by one configuration file. Besides the common inspection angles of 45°, 60° and 70°, the material inspector gets a more global knowledge of the weld quality due to additional sounding angles.
Pre-examinations using CIVA simulation software within the frame of project planning have shown that the inspection of 30 mm thick plates and under consideration of material characteristics and the requirements of defect resolution requires up to 32 parallel channels of the Phased Array device, so that up to 32 elements of the Phased Array transducer are combined to an active aperture (simply put: to the actual sound source) and controlled. Regarding the transducer frequency, 5 – 10 MHz in combination with 32 linear arranged crystal elements have emerged as the best compromise between material penetration, sound beam tilting- and defect resolution capability. A wedge made of Rexolite with a work angle of approx. 40° allows a tilting range of the sound beam of 30° to 75° for transverse waves.
A cable length of 3 meter enables the inspection of large seam sections. A spring loaded wheel encoder for the path-dependent inspection data recording is attached to the probe. The configuration of the Phased Array ultrasonic device as well as the data recording and evaluation is performed via an industrial Laptop PC incl. installed inspection software. The scan evaluation can be directly performed at the place of inspection, because all data are immediately available on the PC in digital form after recording. Distances and time exposure are therefore reduced to the minimum. In total the compact, battery-powered inspection equipment is especially adapted to the rough environment of a shipyard and can be carried and handled by the inspector without any problems.
Phased Array ultrasonic inspection equipment consisting of an industrial Laptop PC, a battery-powered Phased Array ultrasonic inspection device with 32 channels, a probe with 32 linear arranged crystal elements and appropriate wedge for generating 35° – 75° transverse waves in the component as well as spring loaded wheel encoder for the path recording.
Display of the inspection results
A further advantage of the Phased Array ultrasonic inspection in comparison to the conventional manual- resp. a radiographic film inspection lies in the increased amount of information. During and after data recording the material inspector is provided with the following display options:
A- scan: display of the amplitude heights of the reflected ultrasonic signal over propagation time as ultrasonic HF view.
B- scan: color-coded display of the amplitude heights considering the signal propagation time for the configured inspection angles. The B-Scan corresponds to a cross-sectional view of the inspected component.