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Weldline Inspection System for Submerged Arc Spiral Welded Pipe by Ultrasonic MethodDr.D.Dutta & Rajesh Bose
M/s. International Testing & Inspection Agency - Calcutta, India
The strip is ultrasonically examined for laminations over a width of 25 mm along its longitudinal edges. Two 15 mm diameter pulse echo probes on each edge are used for this examination, and the probes are applied to the side of the strip which will be on the inside of the Finished pipe. "I lie equipment will detect along the edge of the strip, a lamination whose length and width are both greater than 15 man.
The strip edge equipment consists of two trailing arm assemblies mounted downstream of the leveling rolls and positioned such that the I inch wide hand covered by the two probes on each edge is referenced to the edge slitting line. Air purges are mounted in VEE formation on either side of the probe assemblies to remove the ultrasonic coupling water prior to welding The two pairs of ultrasonic probes (i.e. two on either side of the strip) are connected to a four channel electronic unit mounted on a base plate, which is attached to the strip feed table housing, Two paint guns, one on either edge of the stripper mounted approximately 300 mm from the slitting line to mark the longitudinal position of detected strip edge imperfections Solenoid valves, paint containers and control equipment are mounted on the same base plate as the electronic unit, The electronic equipment is arranged to monitor the occurrence of signals prior to tile first back wall echo and also to monitor the signal amplitude of the first back wall echo. This is achieved by a min gate system in the electronic unit. The sensitivity of each channel on the electronic unit is adjusted such that the first back wall echo amplitude is 2 cm. display (Fig. 1) screen height. The paint gun units and audible and visual alarm are actuated when: -
For demonstration purposes, the equipment will produce a reject signal at the above sensitivity level from an 8 man diameter flat bottomed hole machined halfway through the strip thickness.
A demonstration test piece used for this purpose is as shown in figure 1.
Note: At one end of the test piece (0.375" thick), 5% of the thickness has been removed to facilitate the electronic equipment gate setting to the minimum strip thickness tolerance
To facilitate tire determination of coupling failure, coupling monitor failure indication for cacti pan of probes has separate audio tones.
|Fig 2: Ultrasonic probe configuration ---X I.|
Compling monitoring facilities exist to check the operation of each testing probe. The two longitudinal defect seeking probes monitor the coupling conditions by coupling to one another. The two transverse defect seeking probes are checked for coupling efficiency by the two separate receiver probes mounted on the longitudinal defect seeking probe blocks The equipment is calibrated against a reference standard,
The longitudinal defect seeking probes are calibrated to both internal and external parallel sided longitudinal notches (N5 depth) on both sides of the welded seam (see Figure 3.).
A 4-channel event recorder operates automatically during each pipe test and also doling tile calibration check. The following are recorded
When the equipment indicates the presence of a weld defect audible/visual alarms will operate along with a paint marking system to indicate the location of the indication and by which probe system it was detected i.e. longitudinal or transverse .
All indication from the weld testing probes are re-checked for reproducibility by reversing the pipe back and checking the original indications.
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