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Diverse uses of advanced ultrasonic inspection technologies for

pipeline manufacturing, construction, and maintenance

André Lamarre, Olympus Scientific Solutions Americas

Abstract

Advanced ultrasonic technology is utilized in many different ways to assure the integrity

of pipelines at different stages of their lifecycle.

In manufacturing plants, in-line automated ultrasonic phased array systems are used to

perform full-body inspection of seamless and welded pipes with very high throughput.

In the field, during pipeline construction, automated ultrasonic techniques are used to

inspect girth welds with high accuracy, offering significant advantages over radiography.

During maintenance, when the pipe is accessible, semi-automated and portable phased

array ultrasonic testing is used to accurately map corrosion degradation.

Phased array technology also features comprehensive imagery that facilitates results

analysis and interpretation, as well as electronic data archiving for easy traceability.

When the pipe is not accessible, long-range guided wave ultrasonic testing is capable of

inspecting long distances of pipe; this is considered a very useful and efficient screening

tool for detecting anomalies.

This paper will review how the use of advanced ultrasonic technology contributes to

pipeline integrity.

Introduction

For years, conventional UT was the standard ultrasonic technique used to verify the

integrity of structures such as pipelines.

More recently, the development of more advanced ultrasonic techniques have

extensively improved the efficiency of ultrasonic inspection. Phased array, time-of-flight

diffraction Time-of-Flight-Diffraction (TOFD), automated UT, and ultrasonic guided

waves are the most popular advanced ultrasonic techniques.

These advanced techniques have shown to be very efficient in improving the integrity of

pipelines, particularly when used at specific stages in the lifecycle. They are used during

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the fabrication of pipes, the construction of the pipeline, and also during pipeline

maintenance.

Advanced ultrasonic techniques

Conventional ultrasonic testing usually consists of a UT flaw detector connected to an

ultrasonic probe, which is manipulated by a skilled operator. The operator interprets an

A-scan signal that represents the echo from reflectors in the part. Conventional UT

permits detection and characterization of flaws, but it is known to be slow and highly

operator dependent. It is also limited in that there is no possibility to archive the data.

Operator using Olympus UT flaw detector: EPOCH 600

Phased array technology

Phased array technology is based on the capacity to electronically modify ultrasonic

beams generated by probes that contain multiple small elements. When these elements

are excited using different time delays (focal laws), the beam is steered at different

angles and focused at different depths. If a long probe is used, the beam can also be

multiplexed along the length of the probe, which simulates a mechanical movement.

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Conventional UT vs Phased array UT

Phased array instruments have the capability to control the probe and the results are

displayed in a comprehensive manner using images such as S-scan, B-scan, and

A-scan plots. Phased array instruments are available as portable, stand-alone

instruments or PC-based instruments, each offering different electronic capabilities.

Olympus ultrasonic portable phased-array instruments: OmniScan MX2 (left); OmniScan SX (right)

Phased array technology increases the inspected volume coverage and the flaw

detection capability through its multi-angled beam control capacity and comprehensive

imaging.

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Time-of-flight diffraction (TOFD)

Time-of-flight diffraction (TOFD) is an ultrasonic technique that relies on the property of

defects such as cracks to diffract energy when the tip is impinged by an ultrasonic

beam. Two ultrasonic transducers, one emitter and one receiver, work in tandem to

inspect the volume of a weld. When a crack is present in the weld, its tips diffract waves

back to the receiver and, using simple trigonometry, the depth of the crack is defined.

The use of the B-scan facilitates the interpretation of the signal and increases the

probability of flaw detection.

Time-of-flight-diffraction principle of operation

Automated ultrasonic testing

Automated ultrasonic testing (AUT) uses powered scanners to move and record the

position of ultrasonic probes. Different types of scanners can be adapted to perform

applications such as girth weld inspection, heat exchanger inspection, etc. Manually

driven scanners can be used for semi-automated ultrasonic testing at a reduced cost.

Different inspection techniques, including conventional UT, phased array, and TOFD,

can be used for AUT, and when used in combination they can improve the reliability of

the inspection.

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Different Olympus scanners: PipeWizard for automated girth weld inspection (left); WeldRover for motorized weld inspection (center); ChainScanner for semi-automated weld inspection

AUT speeds up the process of inspection, increases the repeatability, and reduces the

uncertainties induced by human operation. AUT can be used on-site to inspect a girth

weld, or in a factory to verify the integrity of manufactured parts such as pipes. When

integrated into the production process, AUT is referred to an ultrasonic system.

Guided wave technology

Guided wave technology is used to locate potential degradation such as internal or

external corrosion and metal loss in pipe. While conventional UT provides localized

inspection underneath or in the vicinity of the sensor location, ultrasonic guided waves

are able to screen the entire pipe wall, over tens of meters, from a single inspection

position. The inspection can be done without removing insulation from the pipe.

Ultrasonic guided waves beam propagation principle

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Advanced ultrasonics for pipe fabrication

The fabrication of pipes used for pipelines is regimented by international standards

(including the API 5L specification and DNV standards), which define the level of

integrity required for pipes for specific applications. Since pipelines are subjected to

constant pressure and a failure could result in catastrophe, a high level of quality is

required. Advanced ultrasonic systems allow the manufacturer to meet these strict

standards while maintaining a high rate of productivity.

For example, industrial systems using phased-array techniques are used to perform full-

body inspection of seamless and welded pipes. Fully automated and composed of a

series of phased array probes, industrial systems can inspect carbon steel and high-

alloyed steel pipes. Linear flaws as well as volumetric defects can be detected. Wall

thickness variation and measurement of eccentricity are performed simultaneously.

In such industrial environments, robust and powerful electronics are required. Also, the

use of water wedges enables immersion of the pipe to ensure proper coupling of the

phased array probes.

Zoom on the water wedges assembly of the Olympus Full-Body Inspection System

Advanced ultrasonic testing during pipeline construction

The quality of the welds between two sections of pipe is critical to ensuring the integrity

of a pipeline. Automated ultrasonic testing that combines phased array and TOFD

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permits a reliable inspection of the girth welds and provides multiple advantages over

radiography.

To be able to withstand harsh environments, such as Middle-Eastern deserts and

Siberian steppes, the automated system has to be designed and packaged to resist

over-heating, rain, snow, sand, dust, etc.

This automated ultrasonic in situ system consists of a pair of phased array probes,

which generate multiple beams to cover specific zones of the weld and a pair of TOFD

probes for volumetric inspection, mounted on a fully automated scanner. The weld is

inspected in its entirety in only one pass, and the results are immediately shown on-

screen. Inspectors benefit from comprehensive strip chart imaging to provide quick

assessment of the quality of the weld.

Olympus PipeWizard system in operation(left); Olympus PipeWizard strip chart imaging showing a lack-of-penetration(right)

A major advantage that AUT has over radiography is its capability to measure the height

and depth of an indication. When the height and depth of the indication is known, the

critical length of a flaw for the engineering critical assessment (ECA) can be relaxed,

resulting in less need for weld repair. This has been shown to generate important

savings for pipeline contractors. In addition, AUT does not require the use of chemicals

nor proximity to radiation. AUT inspection is also faster than radiography.

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Lack-of-side wall fusion representations: micrograph (top left); radiography (top right); Olympus PipeWizard strip chart imaging (bottom)

Ultrasonic guided wave testing during pipeline maintenance

Guided wave technology is used to screen in-service pipes and pipelines over long

distances in order to localize areas of concern.

Typically, a collar with low-frequency (10–100 kHz) probes is installed around a pipe.

Excited by a portable electronic unit, these transmit ultrasonic guided waves inside the

pipe wall. While travelling in the pipe, any change of acoustic impedance due to wall

reduction, corrosion, or geometry will reflect energy back to the transducers. The results

are displayed using comprehensive imaging, such as F-scan, C-scan, and A-scan plots,

which provides the means to identifying and localizing areas of concerns.

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Olympus guided wave system: UltraWave LRT

This technique helps to reduce operating costs when inspecting pipes with limited

access. It is recognized as a reliable screening method. In-depth evaluation of the area

of concern is then carried out using other techniques such as ultrasonic phased array.

Phased array ultrasonic testing during pipeline maintenance

To maintain the integrity of a pipeline during its lifecycle, a maintenance program is put

in place to monitor degradation. Corrosion is considered as the main source of pipeline

deterioration.

Corrosion evaluation of a pipeline is performed in the ditch by a crew of operators. For

the sake of practicality, portable battery-operated phased array instruments are used.

Using a long phased array probe mounted on a water wedge, large areas can be

inspected very quickly with an automated or semi-automated scanner. Mapping of the

inspected area is displayed on the instrument, showing the remaining wall values in a

color-coded image known as C-scan.

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Olympus OmniScan MX2 ultrasonic phased-array unit with ChainScanner and Hydroform in operation for corrosion inspection

Conclusion

Advanced ultrasonic techniques contribute significantly to the integrity of pipelines.

When used during the fabrication of pipe, and the construction or maintenance of

pipelines, these techniques optimize the accuracy, speed, and reliability of ultrasonic

inspection.

The accurate and comprehensive images used by phased array, TOFD, automated UT,

and guided wave technology offer considerable advantages for the interpretation of the

inspection results.

In addition, these techniques have shown to be reliable replacements for radiography in

ensuring pipeline integrity.