Quality Test & Inspection: Preserve the Image

August 1, 2006
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When it comes to remote visual inspection, there has been an improvement in overall imaging quality as a result of fully digital data streams and improved optical and illumination technology, which, in turn, has led to a greater probability of flaw detection and improved inspection productivity.



Visual inspection is the oldest of all inspection techniques. Man has always trusted his eyes to assess the quality or fitness for purpose of objects ranging from artifacts and structures to precious stones and food. He also has always trusted his brain to provide him with analysis and management of the input data. However, as engineered products became increasingly complicated, it became necessary to devise other inspection methods. One of these is remote visual inspection (RVI), which still permits the human brain to make critical assessments but allows the eye to travel to previously inaccessible locations.

Inspection, and specifically nondestructive testing (NDT) or examination, is a vital technology for the operation of any industrial plant and in the manufacture of any product. Inspection is carried out to assess the functional integrity of offshore oilrigs, nuclear power stations and aircraft. Inspection is carried out during the manufacture of capital and consumer products from children's toys to automobiles to ensure quality and fitness for purpose. There are many techniques available for such inspections.

Radiography provides volumetric inspection of simple and complex geometry items by using high-energy radiation to penetrate the parts. Ultrasonic techniques, or sound waves much like sonar, can be used to detect and size defects in materials. Eddy current techniques are used to identify near-surface or surface-breaking defects. Very often the first stage, and often the last stage, in any inspection will be a visual inspection. Because of the complexity of much of today's plant and equipment, very often this inspection has to be carried out remotely.



What is RVI?

RVI uses optical and electro-optical methods to allow images to be viewed and captured from otherwise inaccessible locations or where normal access is denied because of interfering structures or machinery. Typical applications include checking for obvious plant problems such as leaks, vibration and misalignment, as well as inspecting for surface cracking, corrosion and erosion, liner integrity, blockages and foreign bodies.



Very often the first stage, and often the last stage, in any inspection will be a visual inspection. And because of the complexity of much of today's plant and equipment, often this inspection has to be carried out remotely. Source: GE Inspection Technologies
Versatility allows RVI to be used in a variety of applications including inside turbines and piston engines, inside conventional fossil fuel and nuclear power plants, on oil production platforms, within pipe work systems-including heat exchangers-inside pressure vessels and storage tanks and in air-conditioning ducts. It also can be used to provide a vision system for remote tooling and in-situ cleaning, akin to the application of endoscopy in the medical field.

Sometimes, a remote visual inspection and report will meet the relevant inspection requirements. Sometimes, RVI will be used to complement other NDT modalities or inspection and measurement instrumentation, such as pressure or flow metering.



Remote visual inspection permits the human brain to make critical assessments but allows the eye to travel to previously inaccessible locations. Source: GE Inspection Technologies

Evolution of RVI Systems

In its most basic form, an RVI system is made up of a lens and an illuminating light source, connected to a light-transmitting extension that ends in a viewing eyepiece. This was essentially the design of the first borescopes, which featured a rigid connection between lens and eyepiece and first appeared more than 70 years ago. It also was possible to record any inspections by fitting a 35-millimeter camera to the instrument. The fiberscope, which uses fiber optics to allow flexibility in the manipulation of the RVI system, was developed in the 1970s and subsequent developments saw the introduction of video CCTV devices, video borescopes and portable video borescopes. However, there have been a number of advances during recent years in the way borescope data is viewed, captured, stored and analyzed. These advances have been founded on the way that digital connectivity has been introduced to RVI.



Source: GE Inspection Technologies

From Data Capture to Data Management

With current and previous generations of RVI equipment, inspection practices have been largely limited to data-capturing processes, using technology such as 3.5-inch floppy disks and VHS videotape. In recent years, advances in technology have significantly improved the ways that inspection data can be captured and saved and, today, digital, full-motion video can be saved using CD, DVD, flash media or other solid-state memory cards. Data can be recorded direct from the RVI instrument, with flash media through a USB connection, and the files can then be transferred to a PC for further assessment or storage. This sneaker-net solution, as it has become known, has continued to provide a workable solution to data storage and data sharing. However, the latest generation of video borescopes now allow complete digital integration of data capture, data transfer and data management, offering significant advantage over the two-step sneaker-net method.

This has been achieved by creating a new generation of video borescopes with PC-standard operating systems, containing integral and intuitive image management software, which can create data folders, organize and delete files and even create reports which automatically integrate saved images or motion-video clips into the report document. Inspection also can be fully documented by combining input for text overlay and voice annotation with the imaging data and multiple video stream outputs allow simultaneous viewing by multiple parties. Information shareability also has been considerably enhanced by stepping up to USB-2 outputs for fast data transfer to portable memory devices and associated PCs, while Ethernet connections enable hardware and software to connect to open Internet lines and to support private network protocols.

These new generation borescopes, with their on-board CPUs, represent a significant advance in processing power. This means that analog-to-digital conversions are reduced to just one, resulting in minimal signal degradation. More processing power also means faster, better and higher resolution image management, which as well as improving general inspection enhances features such as contrast imaging used in the identification of edges and defects in difficult locations. The new borescopes are also well suited for handling the compression formats, such as MPEG-2, which offer a good balance between data transfer rate and the unavoidable, but virtually unnoticed data loss that occurs with compression. Typically, at a bit rate of 1MB per second, today's most advanced video borescopes, with high-specification digital processing capability and multiple video processors, can record more than 1 hour of real-time digital video simultaneously onto a 4GB flash device or a DVD while delivering outstanding image quality.



Application-specific Software

With its integrated PC operating system, today's borescope can be used to browse the Web and communicate through conventional e-mail and other electronic methods, as well as being suitable for the running of application software. Web browsing provides the inspector with immediate access to a useful range of relevant information, while standard and internal company e-mail greatly enhances communication to and from the job site. And the connected video borescope is capable of pumping high quality video into the World Wide Web at rates of megabytes per second.

However, the potential of today's borescopes does not rely solely on their immense processing capabilities but also on the application software available to ensure that the vast amounts of generated data is efficiently managed. Such software can organize the images with meaningful names and standardize inspection processes so that comparable information is generated. It can streamline inspections to focus on only what needs to be inspected and it can create a filing structure and a means to categorize data for analysis thereby significantly improving the quality control process.

It also can guide an inspector accurately through specific inspections, as is the case with the menu-directed software program. For example, when inspecting a turbine, a drop-down menu will first allow the inspector to make his choice from gas turbine, steam turbine, control valve or coolant pump. The inspector can then input all the identification data relevant to that job-name, site, date-before selecting the borescope entry point and carrying out the inspection on the specific, identified component. After the inspection image is captured, the image file is tagged with all the relevant information and filed within the borescope's data capture system. When all the images are captured, tagged and analyzed, paper reports are automatically generated and the data is either saved as individual files or fed into a data warehouse.



Future of RVI is Data Management

Data warehousing or archiving is essential if the vast amounts of data generated by RVI is to be exploited to its greatest extent. Fortunately, one of the greatest benefits of digitization is its potential for information management. Archiving software is now available, which can provide on-line and near-line image storage, single-media archiving by CD/DVD, as well as storage on DVD jukeboxes. As a result, information sharing is simplified and flexible and access to any information is much faster. In one software platform, all data is saved and transferred in DICOM/DICONDE format, a development from the medical sector, which is fast gaining acceptance in industry as the preferred data transport technology. DICOM/DICONDE compliancy ensures that operators are not constricted by current, proprietary formats, eliminates the need for data conversion and simplifies data integration from other NDT information systems, such as pipeline databases.

The flexible and versatile database of the new archiving and storage software also opens the way for developments in data mining, where different databases can be compared and analyzed to investigate the effect that various parameters, such as load, pressure, flow and temperature, have on defect development. This takes NDT and inspection into diagnostics akin to medical diagnostics, where it will be possible to forecast future trends and treat the underlying cause of the defect rather than merely correct the defect itself.

Data fusion also is an area of future software development, allowing the fusing of information from different RVI inspections, as well as the fusing of information from other NDT modalities. This will be carried out using data stored from previous inspections, to provide a better trending and analysis platform. Data also can be compared from simultaneous inspections, such as eddy current information for surface inspection and ultrasonic or radiographic information for volumetric inspection and then even exported to a remote site for comprehensive review and analysis.

RVI has come a long way since the early days of rigid borescopy. There has been a vast improvement in overall imaging quality as a result of fully digital data streams and improved optical and illumination technology, which, in turn, has led to a greater probability of flaw detection and significantly improved inspection productivity. Enhanced data capture technology has enabled higher quality inspection data. The integration of PC operating systems and the associated processing power within borescope workstations has expanded their versatility and greatly facilitated data sharing. Sophisticated data recording and archiving systems allow the plethora of accumulated data to be organized efficiently and used to best advantage. As a result, inspectors can now work smarter and faster, while manufacturers, plant operators and owners have access to accurate and meaningful information to ensure the on-going integrity, quality and safety of their products, plant and assets. Q



Tech Tips

-Remote visual inspection (RVI) permits the human brain to make critical assessments but allows the eye to travel to previously inaccessible locations.

-Sometimes, a remote visual inspection and report will meet the relevant inspection requirements. Other times, RVI will be used to complement other nondestructive testing modalities or inspection and measurement instrumentation.

-In its most basic form, an RVI system is made up of a lens and an illuminating light source, connected to a light transmitting extension that ends in a viewing eyepiece.

-With its integrated PC operating system, today's borescope can be used to browse the Web and communicate through conventional e-mail and other electronic methods, as well being suitable for the running of application software.

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