Mechanical Integrity - Technology and Techniques

Mechanical Integrity's skilled field service operators, technicians and engineers have considerable experience in the practical application of advanced NDE technologies to solve real inspection challenges. See below for an explanation of technologies and inspection techniques which demonstrate Mechanical Integrity's technical leadership.

AUT

(Automated Ultrasonic Techniques)

Crawling AUT robot

Introduction

The TD-SCAN automated inspection system is a development of Technology Design. It applies the TOFD, Pulse Echo, Corrosion mapping, and Phased Array technology to non-destructively screen piping and vessels, such as those found in the refining and petrochemical industries. The user is provided with a true representation of the test material which speeds the process of defect interpretation. All data is digitally recorded and scans are repeatable for monitoring purposes.

The Technology

Automated Ultrasonic inspection uses conventional and special transducers to generate sound in the test materials. These transducers are mounted to robotic crawlers, which articulate to cover large areas of vessel surface. The data collected is then displayed in color in multiple A-Scan, BScan, C-Scan, and D-Scan images A-scan representation is the view in which the signal amplitude is shown as a vertical excursion from the horizontal sweep time trace.

Corrosion mapping

The B-scan and D-scan presentations are two-dimensional views of cross-sectional planes through the test object on different axis. This imaging is helpful in distinguishing mid-wall inclusions such as laminations and blistering, from back-wall discontinuities like erosion and corrosion. The C-scan image is a two-dimensional plan view of the object. Indication of depth is color coded to provide the image with qualities which resemble a topographical map viewed from the inspecting surface.

Pulse-Echo

Pulse-Echo inspection is the process in which discontinuities are detected by the return echoes from the transmitted pulses. This is the most common ultrasonic method used, and usually consists of one or more search units acting individually to send and receive sound. There are several different ways to use pulse-echo ultrasonics and each provides specific information pertaining to the test object.

Corrosion Mapping

AUT corrosion scan Data sample

Corrosion mapping is one of the more common inspections performed today. It provides reliable information about the remaining wall and ID geometries of equipment and piping to engineers and inspectors, who use the information to establish corrosion rates, equipment longevity, and maintenance and repair cycles.

It also provides information on the material integrity, such as laminar defects and blistering, which may occur due to the migration of hydrogen atoms through the material due to process. It is possible to scan up to 800 square feet of surface area per day with the automated system. All vessels and piping systems in the refining and petrochemical industry are subject to material degradation and automated corrosion scanning can help detect where problem areas exist or where they could exist in the future. AUT corrosion scanning provides digital images which can be regenerated or archived for future examination. AUT corrosion scans can be remapped to establish flaw extension over time, for Fitness for Service assessments.

Pulse-Echo Weld Inspection

Above is an example of a Crawler performing AUT Weld inspection

Pulse-Echo weld inspection uses single or multiple search units, set at specific angles, to inject sound into the test weld to search for discontinuities and defects. These angled and zero degree search units can be mounted onto a robotic crawler which enables the inspector to cover large areas of weld in a reliable and repeatable manner, and in a shorter amount of time than doing the work manually. Depending on the thickness of the test material and the angle of the search unit sound path, the crawler rasters the transducers in a perpendicular motion to the weld in order to get full volumetric coverage of the material with the search units. This is performed simultaneously from both sides of the weld. This technique detects, locates, sizes, and identifies the nature of the flaw. Any defects found with AUT weld inspection are manually checked by the certified technician to be sure of reliability. Most vessel and piping welds may be examined with pulse-echo ultrasonics whether they be existing, repaired, or new production. It is the most widely practiced and commonly used technique in weld inspection today. Up to 300 linear feet of weld can be inspected per day with AUT weld scanning.

Zoned Weld Inspection

Above is an example of Manual Encoded Scan System for Zoned Weld System

Zoned weld inspection is another product of AUT weld inspection. The search unit or units, are set at a specific surface distance from the weld, depending again on the thickness and angle used, and focus the sound on a particular area of the weld. The crawler is then used to traverse the weld in a linear parallel to search for defects. Since no raster is needed, this is one of the faster AUT weld inspections and provides detection and flaw length information. It is possible to inspect up to 500 linear feet of weld per day with AUT Zone Weld scanning.

Phased Array

Phased Array technology is one of the latest advances in ultrasonics and provides many useful tools for inspection purposes. An array of transducer elements are excited in precise timing patterns to produce certain desired effects, such as steering the beam axis or focusing the beam. This allows the user the ability to inspect certain portions or volumes of the weld using many different beam angles and focal laws. The results may be viewed as A-scan, B-scan, C-scan, or as a Sector scan image. This technique is also used in a single axis scan motion which makes it faster than manual scanning.

Above is an example of Phased Array Sector and BScan image showing Lack of Root Fusion and Lack of Sidewall Fusion

Above is a Phased Array Probe examining a Half-Inch Weld Sample in a water bath

Above are samples of a Phased Array probe and Wedge.

Time of Flight Diffraction (TOFD)

Time of flight diffraction is an accurate method for detection of flaws for weld inspection. Using two search units, one transmission and one receiver, compression waves are injected into the test material at angles specific for the thickness range. This method introduces both the compression mode of sound as well as shear waves into the material. In most cases, full volumetric coverage can be attained. The display resembles black and white waves or lines since each positive and negative half-wave cycle is recorded according to mode type and position gated in time. Discontinuities are shown as breaks in the waves or additional waves between mode lines. TOFD is much more sensitive than pulse-echo and is a useful tool when sizing defects in welds. The search units can also be attached to a robotic crawler or an encoded manual scan system to quickly inspect welds in a single, parallel line scan motion to provide flaw detection, length, and depth. It is possible to inspect up to 500 linear feet of weld per day using AUT TOFD scanning.

Above is an example of the TOFD probes on a calibration block

TOFD Sample Of A Half Inch Weld

The Scanners and Systems

Each scanning system is designed and manufactured to handle day-to-day service in the rough petrochemical environment. All of the automated crawlers are fitted with coolant systems to help keep them operational when in use at higher temperatures. The crawlers have been used successfully at temperatures of up to 700 degrees Fahrenheit (371.11 degrees Celsius). We also fit special couplant delivery systems to each scanner to help ensure proper sound transmission into each test piece. This provides inspectors with the ability to acquire accurate data even at the higher testing temperatures.

Above is an example of our High Temperature Scanner in operation at 700 Fahrenheit

An Example of our AUT system in operation

AUT Cladding Inspection

Automated Ultrasonic Clad Inspection provides our clients with the data they need to evaluate an equipment's clading condition for remaining life evaluations.

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High Temperature AUT

High Temperature AUT allows recent developments in equipment and technology to be available to the refining and petrochemical industry.

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AUWI

Automated Ultrasonic Weld Inspection - a pulse-echo ultrasonic technology to perform and digitally record weld inspections.

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Mechanical Integrity's services are split into:

Product Solutions: standard or tailored turnkey solutions which meet the rigorous reliability, flexibility and ease-of-use requirements of the petrochemical industry and as tested by our own field service division

Field Servicing Solutions: provision of highly-skilled and reliable manpower to visit your location and provide the optimum NDE solution and onsite reporting

Technical Consultancy: proven and systematic approach to address complex or new NDE challenges

Training: from application training for Product Solutions to UT levels I & II

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