Introduction

A2072 INTROSCAN is an inspection robot system for intelligent pigging of gas pipelines in empty state (free of gas products). The main purpose of the inspection system is detection of irregularities by means of visual and ultrasonic guided wave inspection units on board of the magnetic wheel crawler traveling inside of the pipeline.

The technology and inspection system has been developed by Acoustic Control Systems - ACS Group and is represented in KSA by Isotopes Arabia.

• Transport vehicle

  The wirelessly driven crawler unit can be inserted to the pipeline via available manhole hatches and capable to insect pipelines with OD > 500 mm. The dimensions of the access holes must be > 320x240 mm.

  The inspection of pipelines is provided without additional clean-up operations, at that the scanner moves in a path along the pipe passing-by the contaminated areas.

  The range of robot coverage is 2 km for Straight Sections and 1 km for Elbow and Tee Joints Passage Sections.

  

  

  Fig. 1: Pipeline Inspection by wireless intelligent pigging system INTROSCAN

• Visual screening

  The A2072 INTROSCAN is equipped with two slewing optical HD cameras (1280x720 Pixels) installed in front and on the back of the vehicle for visual inspection of the

  

  

  Fig. 2: Slewing optical cameras for visual inspection integrated in A2072 INTROSCAN

  

  Fig. 3: Near-field image of the front HD camera

• Ultrasonic screening for corrosion and stress-corrosion detection

  The ultrasonic testing of pipelines is performed by means of shear-horizontal guided waves (SHo mode) propagating perpendicular to the traveling direction of inspection vehicle. While moving in axial direction of the pipe the array of ultrasonic Dry-Point -Contact transducers generates and receives guided waves, propagating in circumferencial direction of the pipeline. For detection circumferencially oriented material flaws, e.g. cracks in girth welds, the inspection unit has to travel in circumferencial direction insonifying the pipeline in axial direction.

  Data obtained in pulse-echo mode by transducer array are in real-time transferred to the control PC to be processed by Synthetic Aperture Focusing Techique (SAFT) algorithm. The data processing and evaluation for the inspection results is performed off-line in a separate evaluation software.

  The inspection range of the guided wave inspection is limited by several hundred millimeters in both directions 800 mm depending on sound attenuation value and maximum up to 1000mm both sides. Thus, for covering 100% of pipe circumference several axial scans must be performed.

  DPC transducers applied for sound generation and receiving pulse-echo data require no ultrasonic couplant.

  

  

  Fig. 4: Array of Dry-Point-Contact transducers integrated in A2072 INTROSCAN

• Reference specimen

  The instrument calibration has been performed on the mockup having nominal wall thickness of 9.5 mm with artificially introduced reference reflectors (notches and flat bottom holes) placed at different locations of the mockup. The notches representing crack-like defects have orientation in axial direction (first group of 7 notches) and circumferential direction (second group of 7 notches). Further, flat bottom holes have been introduced representing corrosion-like defects (see Fig. 5).

  It can be stated that longitudinally oriented notches can be detected whale scanning the pipeline in longitudinal direction, while for detecting second group of the notches a circumferential scan has to be conducted.

  Flat bottom holes (FBH) have unidirectional beam directivity and can be detected by any scanning direction. Although, FBH are weaker reflectors and should be preferably detected at smaller distance from the transducer array.

  

  Fig. 5: Locations and dimensions of the artificial defects introduced in the the pipeline mockup

  

  Fig. 6: Mock-up of the pipeline with artificial reference reflectors

• Calibration results

  Figures 7 and 8 represent the results of calibration scan performed in axial and circumferential direction accordingly. In both scans the artificial reference reflectors could be detected with sufficient signal-to-noise ratio. Based on the performed calibration scan the rejection level has been chosen equivalent to the notch with 20% of the wall thickness and length of 20 mm.

  

  Fig. 7 a) Axial scanning direction

  

  Fig. 7b) : C-Scan image by A2072 axial scanning in "1 hour" position with detected artificial reflectors (longitudinal notches)

  

  Fig. 7c) : C-Scan image by A2072 with the thickness range recorded as display below.(9.1-9.4mm)

  

  Fig. 7d) Notch 1 Longitudinal Direction

  

  Fig. 7e) Notch 2 Longitudinal Direction

  

  Fig. 7f) Notch 3 Longitudinal Direction

  

  Fig. 7g) Notch 4 Longitudinal Direction

  

  Fig. 7h) Notch 5 Longitudinal Direction

  

  Fig. 7i) Notch 6 Longitudinal Direction

  

  Fig. 7j) Notch 7 Longitudinal Direction

  

  Fig. 7k) Notch 8 Longitudinal Direction

  

  Fig. 71) FBH 1

  

  Fig. 7m) FBH 2

  

  Fig. 7n) FBH 3

  

  Fig. 70) FBH 4

  

  Fig. 7p) FBH 5

  

  Fig. 7q) FBH 6

  

  Fig. 8a) Circumferential Scanning Direction

  

  Fig. 8b) : C-Scan image by A2072 scanning in circumferencial position with detected artificial reflectors (circumferencial notches)

  

  Fig. 8c) Notch 9 Circumferential Direction

  

  Fig. 8d) Notch 10 Circumferential Direction

  

  Fig. 8e) Notch 11 Circumferential Direction

  

  Fig. 8f) Notch 12 Circumferential Direction

  

  Fig. 8g) Notch 13 : Circumferential Direction

• Inspection of a test section at ARAMCO

  After the calibration scans performed on the mockup of Isotopes Arabia, a trial inspection has been conducted on an ARAMCO object at Shaybah.

• Photos by INTROSCAN

  Figure 9 shows recordings of the INTROSCAN front-camera in the far-field mode (infinite focus), where closed clapper valve and cancellated three-way plug can be observed.

  

  Fig. 9: Far-field images of the front HO camera

  Figure 10 shows the recording of the back camera of the INTROSCAN vehicle with the nearfield focusing, where pulled surface with the slight cracking can be observed.

  

  Fig. 10: Near-field image of the back HO camera

  

  Fig. 11: Far-field images showing welds of the front HO

  

  Fig. 12: Near field images focusing Welding of the back HO camera

  

  Fig. 13: Near field images focusing Welding of the front HD camera

  

  Fig. 14: Near field images focusing Nozzle Branch of the Rear HD camera

• Results of the ultrasonic inspection

  The Figure 15 represent the C-Scan image recordings with the Thickness Chart with Different thickness ranges from 15 to 80mm recorded as displayed below in green.

  

  Fig. 15: C-Scan image by A2072 axial scanning in "2 hour"

The obtained results of INTROSCAN inspection can be summarized as following:

• Trial inspection run at Shaybah plant has been conducted by the INTROSCAN inspection robot after preceding calibration performed on the mockup with artificial reference defects - notches of 20% wall thickness.
• The instrument functionality could be confirmed in "native" environmental conditions (58°C inside of the pipeline).
• Both visual and ultrasonic tests have been performed with no relevant / unacceptable indications.
• Further trials on available mockups by ARAMCO with relevant defects and real objects with natural flaws for the purpose of further verification of the INTROSCAN inspection technology are eligible.