Ultrasonic Application Solutions

Bike Eddy Current Array – Robotic Tank Weld Inspections
Application

Customer challenge

Integrating an eddy current array for detection of

For the magnetic crawler, the Waygate Inspection

surface cracks on carbon steel welds with a remote-Robotics BIKE platform can freely maneuver oncontrolled magnetic crawler robot enables tankmagnetic flat and cylindrical surfaces. Its capability

inspections without personnel having to enter
hazardous confined spaces. Pressure vessels used inthe Oil & Gas industry require regular inspections toassess the integrity of the asset. Today a lot of thiswork is still carried out manually by having inspectors
enter the asset. The confined space nature of theseareas however poses significant safety risks to thepersonnel.
Eddy current array testing (ECA) was chosen due to its
suitability for automaton. Combining this method witha remote-controlled magnetic crawler that can freely
maneuver on carbon steel surfaces removes the needfor personnel entry into the confined space of theto cross concave and convex corners with angles up
to 90° also allows deployments through manholeswithout man-entry or additional deployment tools.
The ECA probe is mounted in a holder that ensuresperpendicular alignment to the surface. A springloaded linear axis in the holder generates a constantcontact force against the weld. An actuated arm
allows the probe holder to be retracted above therobot during travelling and corner crossings.
The 3D Loc module with its 2D Lidar sensor and IMU
can be mounted in parallel to allow the entire 3dimensional inspection path to be recorded into a
mission database. A high definition tilt-zoom
camera can also be added to better monitor thevessel. A sensor carriage engages the eddy current

weld crack inspection or carry out visual inspections

array probe onto the weld with a defined force andwithout having to exit the asset to swap tools.

angle, removing the usually very operator dependent
manual handling of the sensor. With the addition ofThe robot is remotely controlled from the Integrated

the crawler being able to move the probe straight andControl Station usually placed close to the manhole

at a constant speed along the weld, results in a veryof the asset. It can generate an incremental encoder

repeatable and robust measurement.

signal based on the BIKE movement that can be fed
to the Eddy Current Instrument to record continuousC-Scans.

Solution benefits:
Pressure vessels used in the Oil & Gas industry require regular inspections to assess the integrityof the asset. Butt-welds connecting the plates which make up the shell of a tank are subject tovarious damage mechanism, many of which appear as surface cracks that can lead to failure ofthe entire asset.

Today a lot of this work is still carried out manually by having inspectors enter the asset. The
confined space nature of these areas, however poses significant safety risks to the personnel.
Any rescue efforts also inevitably expose rescue personnel themselves. The need for internalcleaning and scaffolding before an inspection both further increases the duration of stay in thehazardous area, as well as the outage duration and associated costs. Hence the chief goal ofdeveloping this new weld crack inspection tool was to avoid confined space entry and minimize
overall time spent inside the asset.

For the inspection method, eddy current array testing (ECA) was chosen due to its suitability forautomaton. Single-pass coverage of both weld and heat affected zone allows unmatchedinspection speed at reliable and uniform coverage. The ability of eddy current to inspect throughnonmagnetic surface coatings removes most requirements for prior surface treatment.
Complete C-Scan can be created by adding just one encoded axis in scan direction. Combining
this method with a remote-controlled magnetic crawler that can freely maneuver on carbon
steel surfaces removes the need for personnel entry into the confined space of the vessel.

A sensor carriage contacts the eddy current array probe onto the weld with a defined force andangle, removing the usually very operator dependent manual handling of the sensor. With theaddition of the crawler being able to move the probe straight and at a repeatable and robust
measurement.

Test Equipment:Eddy Current Array Probe with Tester
oProbe cable – 30 meters (~100 feet)o40 Probe coils – 2 mm diameter eachoArray coverage – 52 mm (2 inches)oMaximum weld bead height: 0.197 in. (5 mm)o

Minimum detectable crack (L x W x D):
0.020 in. x 0.004 in. x 0.020 in. (0.5 mm x 0.1mm x 0.5 mm)oMaximum penetration depth: 0.039 in. (1 mm)(Stainless Steel)Inspection Technique
The system was designed to inspect welds manufactured tothe quality standard ISO 5817 for surface imperfections. Hencethe eddy current equipment and procedure follows therequirements for eddy current testing techniques according toISO 17643. For calibration, a block as described in ISO 17643
with three continuous cuts of 0.15±0.03 mm width and depths
of 0.5±0.03 mm, 1.0±0.05 mm and 2.0±0.10 mm is used. Plastic
shims allow for consideration of surface coatings.
A weld reference block has been designed to validate theperformance of the system. EDM notches represent surface
breaking weld flaw locations and sizes as described in the ISO
5817 weld quality standard. Notches are placed on the weld
bead, weld toe and parent material.
Each notch is 6.0 mm long and 0.15 mm wide. Each location isrepresented with a set of transverse and axial notches ofdepths 0.5 mm, 1.0 mm and 2.0 mm.
The Surface Array Probe and Eddy Current instrument waschosen to meet these requirements. Two arrays of 20 coils at apitch of 2 mm enables detection of longitudinal, transverseand off-axis cracks as short and deep as 0.5 mm. The array
width of 52 mm (2 inches) allows single-pass coverage of
weld widths up to 22 mm and 10 mm parent material to eachside while leaving another 12 mm margin for following theweld. The flexible face of probe carrying the coils can contour
to weld bead heights of up to 5 mm. This system can detect all
artificial flaws on the weld reference block, including the mostcritical 0.5 mm deep notch at the weld toe. Lift-off tolerance isvery high with the system still being able to detect every
artificial flaw at an additional epoxy coating of 0.5 mm
thickness.