Specialist Inspection Services and Equipment from Silverwing

Long Range Ultrasonic Inspection (Guided Wave)

Guided wave provides a method of rapidly determining where there are problem areas on a pipe. There are many possible applications for guided waves for rapidly screening long lengths of pipes.

Instead of scanning the region directly below or near to the transducers, guided waves travel down the length of the pipe. This allows 10's of meters to be inspected from a single location.

The pipe walls form a guide for ultrasonic waves, which directs them down the length of the pipe. When the guided wave hits a change in cross section it reflects back toward the transducer.

Some applications where this technology is especially cost effective are listed below. Areas such as road crossing, which cannot currently be inspected without excavating, can now be quickly screened to determine which are in danger or corrosion.

Rapid, full coverage screening of pipes
Especially cost effective in difficult to access locations

Road crossings
Corrosion under insulation
Riser Inspection
Deck penetrations
Wall penetrations
Pipe racks
Rope access
Underground Pipe

Can detect cracks and general metal loss (greater than 5% of the cross-sectional area)

The equipment is completely battery operated and can therefore be quickly and easily deployed on site.

Although the unit is not rated as intrinsically safe, it will not create an ignition source under normal condition. The low power voltage is safe for the operator. There are no known health hazards involved in using the equipment. The most dangerous part of the performing the test is accessing the test site.

The data is presented in a format that is easy to trace for Quality Assurance purposes. Time stamps, compact file sizes, and calibration values that very with each test guarantee that a test was actually performed.

Long Range Ultrasonic capabilities

100% of the pipe is inspected (within the diagnostic length of a test)
Pulse echo type operation provides information on feature position and approximate size
Can be performed without taking the pipe out of service
Sophisticated analysis aids interpretation of results

Some major advantages of the technique are:

The inspection can be performed without taking the pipe out of service. Tests can even be performed at elevated temperatures (normally up to 120 degrees centigrade, but this range can be extended if special procedures are used).
The entire volume of the pipe is inspected. It does not sample at only spot locations, it is sensitive to corrosion anywhere on the circumference. It is equally sensitive to both internal and external corrosion.
The technique works by looking for reflections from changes in cross section of the pipe. Long ranges of pipe can be screened from a single location.

How Guided Wave works

To perform the guided wave test, a ring of transducers is placed around the pipe. No couplant is needed. The transducers dry couple on to the pipe. The surface of the pipe usually does not need to be prepared. Any loose flaking paint or corrosion needs to be scrapped off of the pipe, but other wise, no preparation is necessary. For example the pipe shown would require no preparation.

Overview of operation



	Small Diameter Pipes Tested using solid rings For pipes 1 - 8 inches diameter Can be mounted in less than a minute 3 inches clearance needed around pipe For pipes 8 inches and under, we usually use solid rings such as the one pictured. They can be quickly mounted on a pipe and have proven to be very durable. Internal springs are used to couple the transducer elements onto the pipe.

		Large Diameter Pipes Tested using inflatable ring For pipes 6 inches or greater Employ conventional foot pump to inflate 2 inches clearance needed around most of pipe For larger diameter pipes, an inflatable belt system is used. This system uses a regular foot pump to fill an internal bladder, which forces the transducer elements onto the pipe. The system allows for a light flexible application of the technique to large diameter pipes. Our normal range of inflatable rings is from 10 to 24 inches in diameter. However, larger. We normally recommend that this screening technique is only used on pipes 24 inches in diameter and smaller. (Larger pipes can be inspected, but on large pipes only large corrosion patches can be found.)


	Testing overhead line In addition to road crossings, other difficult to access locations are frequently screened. Here is an example of a location where a pipe ‘jumps over’ a road. The overhead section has been quickly screened without using scaffolding. An area of increased corrosion has been easily identified.

	Example of Offshore Riser Inspection Testing of 24” Riser. Note the lack of Scaffolding.


	Inspection of River crossing Inspection of 4” to 20” lines across a river. The entire crossing can be inspected from two locations, reducing the amount of access required.



	Inspection of flow lines and Jetty Lines.



		Buried Pipelines



	Road Crossing Inspection