New tool ensures girth welds in oil and gas pipes are right first time

Citation

(2010), "New tool ensures girth welds in oil and gas pipes are right first time", Sensor Review, Vol. 30 No. 3. https://doi.org/10.1108/sr.2010.08730caf.004

New tool ensures girth welds in oil and gas pipes are right first time

Article Type: Mini features From: Sensor Review, Volume 30, Issue 3

A new, groundbreaking internal weld inspection system has been launched that inspects the internal size and shape of girth welds on pipes that are destined for use in deep sea subsea oil and gas applications.

The Internal Weld Scanning Tool, developed by UK-based company Optical Metrology Services Limited (OMS), is an innovative system that internally scans welds inside pipes – both visually and dimensionally – enabling engineers to quickly and confidently assess the quality of the root weld.

In oil and gas pipes, the quality of the root pass of a weld is critical to the structural integrity of the girth weld. Oil and gas companies therefore have stringent inspection requirements for checking welds. However, few if any tools currently exist on the market that can perform this kind of work. Welding of clad pipe is especially 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.

The technology can be deployed onshore and offshore at different stages of the pipe welding process. The 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. The tool 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.

The system 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.

In the past, some engineers would inspect the girth weld at the final stage of the welding process (AUT inspection) – if a defect were found at that stage the delay could be in excess of 4 h. Most reported “AUT” defects are in the root region of the weld. “You need to get the root weld right first time,” says Gooch. “This then ensures that there are no delays in the welding process. The root weld geometry can be checked before the next welding passes and any defects dealt with prior to subsequent passes. This results in fewer defects at the automatic ultrasonic testing stage [AUT inspection] and improves overall productivity and efficiency.”

The OMS Internal Weld Scanning Tool comprises two main systems: a high quality digital colour camera with sophisticated optics and lighting, as well as a high resolution laser scanner. The tool can be used to detect a wide range of weld features, including root penetration, root concavity, cracks, lack of penetration, discolouration, oxidisation, surface porosity and burn-through. To ensure that all these features are detected, the scanning system measures a 25 mm wide cross-section, with complete profiles at millimetre intervals around the inside diameter of the pipe. The camera takes overlapping pictures around the pipe for review and archival.

Software provided by OMS enables the user to document and interpret these features, as well as measure the cross-sectional data. Scanning a typical 10-, 12- or 14-inch diameter pipe takes around 45 s in total. Once the automated scanning of the root weld is complete, the OMS software enables the user to identify the features of the weld and measure them. Cross-sections around the weld, for example, can be chosen and the main features of the weld then measured.

The software also acts as 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.