Video inspection and internal weld scanning
28 October 2010
Hugh Davies, head of sales at OMS, discusses how video inspection and internal weld scanning tools are being used to check weld quality on pipes and other deepsea subsea oil and gas structures.
When inspecting the inside of pipelines and other subsea structures, such as valve manifolds, video inspection can provide close-up views of features that are otherwise very difficult to access. Video inspection enables inspectors to assess a variety of features relating to welds, internal corrosion, internal structure and coating.
Whether onshore or offshore, inspectors need the best possible lighting and video technology, as well as a variety of methods of deploying the video tools inside different structures. Optical Metrology Services (OMS) offers a range of video inspection equipment, including pan-and-tilt camera technology, auto-focus zoom lenses, tractor systems and motorised cable reels.
For specialist weld inspection applications, it is possible to produce bespoke digital imaging solutions - for example, for deployment inside hot pipes during production welding. OMS can also offer a turnkey solution employing its own trained staff.
For ‘reeling trials’, OMS offers video inspection services that can be combined with laser scanning of pipes to provide a combination of imaging and dimensional mapping of pipes or features in 3D.
Internal weld scanning
In oil and gas pipes, the quality of the root pass of a weld is critical to the structural integrity of the girth weld. There are, therefore, stringent inspection requirements for checking welds. However, few if any tools currently exist that can perform this kind of work. Welding of clad pipe is particularly challenging and requires accurate measurement of the weld area in order to ensure zero defects and to avoid the delay and cost of a weld cut out later in the welding process.
Using its innovative internal weld inspection system, in combination with video-based inspection systems, OMS is able to check the internal size and shape of girth welds on pipes that are destined for use in deepsea subsea oil and gas applications.
The Internal Weld Scanning Tool internally scans welds inside pipes, both visually and dimensionally, enabling the quality of the root weld to be quickly. The tool is available on a service contract or rental basis, with a trained OMS inspector.
The service is available both onshore and offshore at different stages of the pipe welding process. The internal weld scanning tool can be used on corrosion-resistant alloy-lined pipe to identify sour (aggressive) ingress points, in both clad butt-weld and clad weld inlay applications. It can also be used to improve weld procedure development efficiency and to check the root weld and geometry before next passes are deposited. The technology provides similar uses in fatigue-sensitive applications (SCRs) where the pipe is subject to higher dynamic stresses.
Using OMS’ internal weld scanning service, a wide range of weld features can be detected, including root penetration, root concavity, cracks, lack of penetration, discolouration, oxidisation, surface porosity and burn-through.
The Internal Weld Scanning Tool can be mounted to a purge dam, with an integrated camera for positioning and inspection. Pipe can be inspected whilst it is being spooled onto a pipe laying vessel or during stalk fabrication/tie-in. Here, the tool is retrieved using a winch and wire system, with weld positioning controlled by a camera and precision motorised system.
The service includes integrated analysis software, which enables the documentation and interpretation of internal weld features, as well as the measurement of cross-sectional data. Scanning a typical 10-, 12- or 14-inch diameter pipe takes around 45 seconds in total.
The software is also a traceability tool. Inspectors can choose cross-sections around the pipe at regular angles and log any defects as they are found. The software automatically records all measurements, as well as typed comments from the inspector. This information, including sample images and cross-sectional profile data, can then be archived. Logged data can be directly imported to Microsoft Excel as part of a weld inspection record.
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