We would like to give you information about further developments about our method to determine corrosion at the supports of pipes.
In March 2009 (last information) we did have experience in testing wall thicknesses up to 15 mm and diameters up to 48". At this moment we have expanded the range up to 40 mm wall thickness and up to diameters of 64" or even higher. In case of an urgent emergency we can offer 10 teams for testing pipe supports. In this way we are able to test approximately 3000-3500 pipe supports in 1 week (7 days). This is equal to 20-25 kilometer of pipe line.
In 2010, we have been asked the following questions.
Is it possible to determine corrosion in positions which can't be reached with our standard
tools. For example in pipes going through walls, floors/ceilings or in drums lying in saddles. We have developed a single-probe-system for this and we are able to say if there is corrosion present, and whether this corrosion is light, medium or heavy. Determining the remaining wall thickness is not possible with this system (see appendix 1).
The single probe system can also be used to determine the extend of the corrosion in circumferential direction. We have developed special tools (for testing in longitudinal direction to determine the exact wall thickness.
We are able to determine the size of a field with corrosion, and to locate the deepest spot.
Is it possible to test pipe supports when there are welds present? We have some situations simulated to show that even with welds it is possible to determine corrosion.
Appendix 2: Corrosion in a trunnion support and the search for it. It is also possible to examine bends with a welded pipe on it.
Appendix 3: a situation with welded double plates. The difference between the area without and with corrosion is clearly visible.
Appendix 4: a situation with a support in 6 hour position, in this case with 1 plate. Even with 2 plates the result is the same. One can clearly see the difference between the healthy material and the spot with corrosion.
Appendix 5: in pipes is erosion present in 6 hour position. At the support a construction is welded to the pipe. Will it be possible to determine the remaining wall thickness at this construction? With pictures we show you that this is possible.
As you can see by our examples we are able to detect corrosion in pipes at different types of supports, clamps and through walls. In case a situation is new to us, we will try to find a fitting solution.
The situations in appendix 1 through 5 we have shown you are part of our revised procedure of November 2010.
In 2010 questions have been asked about detecting corrosion in coated pipes. We have experience with bitume coating since 1998. We inspect isolation couplings and when the pipes do have higher diameters we have to pass a band of up to 500 mm of bitume coating to examine the coupling.
We show you with a 10" coated pipe that it is possible to determine the corrosion. We did also a test with a new coating, named Stopaq. In both cases it is possible to inspect the material over some distance, see appendix 6.
We hope that with these developments from our side it is possible to solve questions from your side. Together with these developments we would like to attend you on our other specific kinds of UT- testing, see appendix 7. On the last 2 pages you'll find our reference list
Short information about our test method
A common form of outside corrosion occurs, when pipelines are lying on steal or concrete, or are hanging in clamps. Because of temperature changes, the pipeline is moving over the support, which can cause damaging of the coating of the pipeline. In combination with water, corrosion will occur. The method of lifting and inspection during process is not acceptable because of the risks which are involved.
In 1997 we received the question if it was possible to detect corrosion in piping lying on supports. In 2002 our procedure was operational and we could offer this service to our clients. Nowadays we test on a yearly base worldwide 30.000 supporting points.
In 2002 our procedure was operational and we could offer this service to our clients. Nowadays we test on a yearly base worldwide 30.000 supporting points.
Method of investigation
Verkade NDT Services has developed a method of investigation to detect in a quantitative way possible corrosion at supports/pipe clamps, and to measure the depth of the corrosion.
The investigation is based on ultrasonic testing and the principle is like this: one probe sends a sound pulse through the material and another probe receives it. Make the signal visible on the screen of a ultrasonic equipment en adjust it to a certain screen height.
If there is loss of wall thickness, the direction of the sound beam will be changed, less sound will be received and the signal on the screen will be smaller.