There is a growing need within the pipeline industry for fast, reliable techniques to inspect piping for corrosion. Olympus NDT has recently released a system to accurately detect and measure corrosion for both large areas of erosion and tiny pinholes.
Ultrasonic (UT) thickness measurement has been used for many years as a simple corrosion mapping system. The system requires marking out a grid on the area of pipe to be tested so that a UT technician can take measurements with a thickness gauge and a conventional ultrasonic transducer. Such measurements can be very accurate, but the process is time-consuming and requires patience. The alternative to corrosion mapping is fully-automated systems requiring expensive robotics.
To provide a middle-range solution, Olympus NDT has just released the Hydroform Corrosion Mapping System. The aim is to provide accurate and reliable results with:
* Simple mechanics;
* No calibration;
* Minimal setup files;
* Simple training for a technician familiar with weld-testing; and,
* Battery operation (up to six hours with two Li-ion batteries).
The system consists of the standard Omniscan MXU phased array (PA) UT flaw detector and the Hydroform scanner, which includes a 7.5 megahertz PA probe and in-built encoder. It can be used either manually or with a chain scanner for full x-y encoding.
The Hydroform differentiates itself from other mapping systems because, instead of a hard plastic wedge, it holds a water column that conforms to the pipe, like a mini-immersion test. A special gasket also minimises water loss.
Advantages of the Hydroform system
The Hydroform Corrosion Mapping System has a number of advantages. It is able to detect mid-wall defects as well as internal corrosion due to high near-surface resolution (NSR). The Hydroform can measure 1.5-2 mm beneath the near surface of the pipe, depending on material and surface condition.
In addition, the system provides stable and consistent coupling between the probe and the pipe surface, regardless of surface condition. This is very difficult with systems that use a large plastic wedge.
Olympus’ system also fits a broad range of pipe curvatures and diameters without the need for many different curved wedges or mechanical setups. Either manually or with the chain scanner, Hydroform can be used on pipes from 100 mm in outer diameter, on flat plates, and on spherical or elliptical pressure vessels.
The 64-element PA probe provides scans approximately 60 mm wide, with 1 mm resolution in both the scan and index (x and y) directions, at speeds of up to 100 mm per second.
The pictured screencap is of a C-scan in which both a band of corrosion and an isolated pit (in red) can be seen. Thickness is indicated by colour, with blue being the nominal wall thickness and areas of increasing wall loss being shown in yellow and red.
Inspection, analysis and reporting of internal corrosion can all be done on the standard Omniscan – no specialised software is required.
The Hydroform system can also be used in conjunction with Olympus’ Tomoview software. Using Tomoview, data files can be merged into one large file, more advanced analysis can be performed, and data can be exported in a number of different formats. For example, tabulated text files can be imported into third-party evaluation software such as Technical Tool box.
For more information contact Alison Glover at Olympus Australia on 0418 351 021 or email alison.glover@olympus.com.au