Flooded Member Detection is an inspection regime designed to screen subsea platform structural members for defects. A cracked weld, for example, can allow the ingress of sea water into the member which may 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.


There are two recognized non-destructive testing techniques that allow for Flooded Member Inspection; the use of a radioactive source (commonly referred to as the Gamma Technique), or using Ultrasound.

Inspection using a radioactive source is effective and can be fast – as the source does not need to physically touch the Member and therefore no cleaning or surface preparation is required.

But Cygnus Instruments has embarked on a full development and trials cycle because the UK-based ultrasonic specialist believes that a fully developed, professional UT system can now play a much greater role in FMD in the future.

This is because while some degree of surface preparation is needed for Ultrasonic Testing (UT) of 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 come 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 good cost saving for the operator.

In addition, as the Cygnus system is able to sit on a vessel without incurring personnel costs, it means that an operator and its inspection contractor can perform small packets of FMD inspection work as and when it is convenient; a vessel is not tied to meeting a third-party inspection service provider offshore at a certain time in a certain place. With the Cygnus system, work can be done as and when it suits.


The Cygnus UT FMD system is the only system available to buy that is designed by dedicated ultrasonic non-destructive testing specialist. To that end, when the Cygnus system presents a Flooded / Not Flooded result, that result is backed up with a true UT A-Scan. This allows for more interpretation of a result and that the technician is properly informed.

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