OMS fits Scancontrol into internal weld inspector

Micro-Epsilon is using non-contact laser-profile displacement sensors for an internal weld inspection system.

The sensor measures the internal size and shape of girth welds on pipes destined for use in subsea oil and gas applications.

Optical Metrology Services Limited (OMS) has integrated Micro-Epsilon's Scancontrol 2700 laser profile sensor on its new Internal Weld Scanning Tool.

This tool internally scans welds inside pipes - visually and dimensionally - enabling engineers to quickly and confidently assess the quality of the root weld.

OMS is a specialist measurement technology company that provides measurement services and precision measurement systems to the oil and gas industry.

A key focus for the company is in the dimensional measurement of oil and gas pipes or other similar structures such as aero engines, process-industry tubes or manufactured cylindrical objects, where dimensions are critical.

In oil and gas applications, 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 to ensure zero defects and to avoid the delay and cost of a weld cut out later in the welding process.

The Scancontrol 2700 is Micro-Epsilon's latest generation of laser profile sensor.

The compact design and integrated controller make the unit ideal for industrial automation tasks and machine-building applications, where space is often restricted.

Other than weld measurement, typical uses for the sensor include the measurement of angles, channels, gaps, edges and clearance; detection of beads (bulges or bumps) of adhesive; door-edge detection; robot guidance and positioning; groove width and depth measurement.

Unlike conventional laser line scanners, the Scancontrol 2700 provides an integrated controller in the sensing head.

The user requires no other components to evaluate the measurement data.

The unit is easy to set up, configure and adapt for different applications.

Measuring ranges are from 25 or 300mm.

Data is output from the sensor via Firewire IEEE1394.

Additionally, a small output module for DIN rail mounting is also available to convert the sensor output data into common fieldbus systems, including CANbus, Profibus DP, Ethercat and IEEE.

The OMS Internal Weld Scanning Tool comprises two main systems: a high-quality digital colour camera with sophisticated optics and lighting, as well as the Scancontrol 2700 sensor.

The tool can be used to detect a 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 25mm-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-in diameter pipe takes around 45 seconds in total.

Richard Gooch, director of technology at OMS, said: 'Not having to connect the sensor to a separate controller was also a key selection criteria for OMS, as there is no space to accommodate a remote controller for this particular application.

'The Scancontrol 2700 also outputs the dimensional data in a format that's easy to manipulate.

'The Scancontrol 2700 measures up to one-thousand profiles per second, allowing us to scan the diameter of a pipe in 45 seconds.

'For inspection of oil and gas pipes, our customers require a system resolution of typically less than 0.1mm.

'To achieve a system resolution such as this, a sensor is needed that is much more accurate.

'The Scancontrol 2700 has a resolution of less than 10um and an accuracy of less than 50um, which helps compensate for other external influences on system accuracy, such as mechanical-system components and thermal expansion.' The Scancontrol 2700 is the first high accuracy profile sensor with integrated electronics in a compact footprint.

Other competing profile sensors on the market with integrated controllers are either very bulky, often two to three times larger, or their measurement performance is reduced because of the restriction in space for the processing electronics.

The Scancontrol 2700 uses the laser-line triangulation measurement principle.

The sensor has an integrated, highly sensitive CMOS array, which enables measurements of almost any surface, including shiny or reflective surfaces, independent of the reflection from the target.

This means excellent accuracy, resolution and reliability are achieved, even at high measurement speeds.

A line optical system projects a laser line onto the surface of the object being measured.

The back-scattered light from the laser line is registered on a CMOS matrix by a high-quality optical system.

Along with distance information (z-axis), the controller calculates the true position along the laser line (x-axis) from the camera image and outputs both values in the sensor's 2D coordinate system.

A moving target or traversing sensor generates a 3D representation of the object being measured.

The system itself comprises a sensor and integrated controller, which calculates the dimensions of the weld.

The system works in two ways: either in a stationary mode, with the sensor fixed and looking at moving targets, or in a scanning mode, where the sensor works in combination with a motion-control device or robot.

The sensor uses an innovative CMOS array with a real time, high-speed electronic shutter (rather than conventional rolling shutters), which captures the entire profile and processes the information instantaneously.

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