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Flooded Member Detection is an inspection regime designed to screen subsea platform structural members for defects. A cracked weld, or similar, can allow the ingress of sea water into the member which may go on to create a point of failure for the structure. Operators therefore inspect these members on a regular basis to gain confidence that there has been no sea water ingress.


The Cygnus Flooded Member Detection (FMD) system is the only one of its kind available that is designed by a dedicated, ultrasonic NDT (Non Destructive Testing) specialist. When the Cygnus system presents a Flooded / Not Flooded result, that result is backed up with a true, rectified A-Scan. This allows for more interpretation of a result and allows either the technician on the survey, or an off-site engineer at a later date, to confirm the result is absolutely correct.

Other considerations have also been taken properly in to account; there is a 4-way gimble built around the Cygnus transducer that ensures correct transducer alignment; and the system has a transducer contact sensor – to let the topside technicians know the ROV or diver has made good contact.

“Over the past few years, we observed that FMD with UT (Ultrasonic Testing) has not gained as much respect from the offshore inspection industry as it should have done,” says Cygnus Managing Director Lucinda Crosthwaite-Eyre. “Previous generations of UT equipment were not dedicated to the task and could be tripped up by thick walled members or by heavy corrosion. So we embarked on a full development and trials cycle because we knew that, done properly, a fully developed, professional UT system would play a much greater role in FMD in the future.”

And it would certainly seem as if Cygnus’ intuition was correct.

Nearly two dozen systems have been deployed around the world in the first full year of the product being available -and Cygnus have joined forces with Ashtead Technology to ensure the FMD system is available for rental all round the globe.

Surveys have now been successfully completed by all the major contractors for almost all of the Tier 1 Operators; from Saudi Arabia to the Gulf of Mexico and from Western Australia to the North Sea.


Louis Pietranek of Westerton Access rented the Cygnus FMD equipment from Ashtead in 2018 and commented “The new Cygnus Ultrasonic FMD System was perfect for our recent application. Our technicians found the software to be very easy to use with features that ensured a quick and reliable result. It’s a great addition to the Westerton Access capability, offering FMD inspection from the Falcon ROV.”

Customers are clearly appreciating and benefitting from the Cygnus FMD System’s cleverly designed features. Lucinda Crosthwaite-Eyre continues, “after exhaustive development work, our system’s advanced signal processing and low noise data acquisition will work on thick-walled members and pipes (up to 75mm thick), on heavily corroded members and on buoyancy tanks.”

Cygnus has been in the underwater inspection business for nearly 4 decades. And Cygnus Business Development Director, Graham Haines, recalls that “we were asked repeatedly for a UT FMD solution many dozens of times over the last decade - as a result of a lack of reliability from other UT offerings and due to the relative expense of using the gamma technique. But the simple fact was we were always busy on another project. We finally were able to give ourselves some time and space to assess the market and quickly saw that there was a clear space where Cygnus could play. We are all extremely pleased with how the product is now being received.”

Feedback is clear on just why the FMD system is working so well for the world’s biggest contractors: while some degree of surface preparation is needed for UT FMD on Members, that perceived disadvantage can very often be outweighed by two distinct advantages: operational flexibility and cost savings.

Because the Gamma Technique uses a radioactive source, the equipment is almost always provided as a service by a third-party contractor. To operate the equipment one, or often two, specialist technicians must be deployed with the equipment - and they will then take up precious bed-spaces offshore. The Cygnus UT equipment is extremely easy to understand and simple to operate; therefore, existing personnel from the diving or ROV team will perform the inspection work themselves – creating a potentially very valuable cost saving for the operator.

For more information on Cygnus’ latest innovative development, please visit:

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