This case study demonstrates the capability of the Wavemaker System to screen long lengths of pipework from a single location. In this case the test was performed on a 3 inch pipe which was not coated and was lying directly on the ground. The pipe carried light crude oil and was tested while in-service. Visual inspection of the pipe was difficult due to its length and vegetation coverage but the general surface condition of the pipe was good.

The Wavemaker result for the section of the pipe in the photograph is shown opposite. A minor corrosion patch was found and has been marked +F1. A major defect was found close the weld marked +F2. The pipe section after this weld marked +F3 shows very high attenuation which indicates heavy general corrosion. This finding was later confirmed using standard UT measurements

As a result of this test the client was able to limit follow-up inspection and maintenance to the areas of pipe which were found to be defective. This considerably reduces the time and cost of these activities.

Wall penetrations are a common feature within oil and chemical plants where walls are built to control spillage of products and possible flooding. Walls of this type are between 150 and 400mm thick and are usually made from concrete. There are two common types; 'Built-in' where the pipe is simply cemented into the wall during construction and 'Sleeved' where a larger diameter sleeve is cemented into the wall providing a conduit for the pipe.

 

The pipe region within and around a wall penetration is susceptible to corrosion but is inaccessible for visual and conventional Ultrasonic Testing (UT). As a compromise, UT measurements are often taken at a single point on the pipe near the penetration and compared over time to give a general indication of pipe condition. This method cannot give any indication of the condition of the pipe within the wall.

Guided wave inspection using the Wavemaker Pipe Screening System (WPSS) offers a solution to this problem by inspecting the pipe within the penetration and its surroundings for corrosion and other defects from a single convenient to access location some distance away from the wall.

The three case studies which follow demonstrate the WPSS capabilities on various real wall penetration cases.

The above photograph shows two typical 'built-in' wall penetrations within a petrochemical plant. The UT testing points for the pipes are indicated. The standard UT measurements and visual inspection suggested that no corrosion was present in either pipe.

The figure opposite shows the Wavemaker result for pipe A. The location of the wall is indicated by the shaded region at the top of the diagram. The entrance to the wall is labeled F1. No reflected signals were detected from the entrance or from within the wall. This indicates that no significant defects are present.

The figure left shows the Wavemaker result for pipe B. Again the entrance to the wall is labeled F1.A large reflected signal was detected from the area within the wall. This signal also has significant asymmetric content (indicated by the red trace). This result indicates that there are significant defects such as corrosion within the wall penetration.

 

Sleeved wall penetrations

The figure opposite shows the Wavemaker result for a pipe which passes through a sleeved wall penetration. A large and asymmetric signal was detected from the entrance to the sleeve which indicates the presence of a significant defect.

These results have demonstrated the capability of the Wavemaker Pipe Screening System to screen pipes within wall penetrations. The system is also ideally suited for screening long lengths of pipework in difficult to access locations such as: pipe in racks, jump overs and insulated pipes.

This case study demonstrates the capability of the Wavemaker Pipe Screening System (WPSS) to screen long lengths of overhead pipework from a single easy to access location. In this case the test was performed on a 3 inch pipe which was tested while in-service. Visual inspection of the pipe was difficult due to its length and height from the ground but the general surface condition of the pipe was lightly corroded.

The photograph opposite shows the pipe under test. The pipe initially runs at ground level and then turns upwards through a 90 degree cast bend. There is then a 5 meter long vertical section before the pipe turns back to the horizontal through another 90 degree cast bend. The WPSS equipment is mounted to the vertical section of pipe just above the lower bend. From this location it is not only possible to test the vertical section of pipe but also around the bend and along the horizontal section also. The total range which can be tested depends on general pipe condition and coatings but in this case more than 20 meters were tested in each direction.