Cygnus FMDUltrasonic Flooded Member Detector

Issue 4 9.2018

Graham Haines Scott StephenBusiness Development Director NDT Sales ManagerCygnus Instruments Ltd Ashtead Technology

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Flooded member detection (FMD) using ultrasound is performed

by emitting an ultrasonic pulse into a pipe/member

Ultrasound propagates through the near wall of the cylinder. If the

cylinder does not contain water, virtually all of the sound is contained

in the near wall and a flood is not detected, however if the cylinder

does contain water, sound travels through the water and is reflected

off the second (far) wall as an echo and a flood can be detected.

Introduction

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Cygnus FMD System

• Purpose designed for the application of Flooded Member Detection

• It is robust & easy to use, providing a quick result without using a

gamma radiation source (therefore easy to transport, no export

permits/licenses required)

• It gives reliable & repeatable results using advanced algorithms to

‘tune’ the system for differing operational conditions

• For use on members which are horizontal, vertical & diagonal

with a wide range of wall thickness & member diameters

• Good performance on corroded members due to the use of a

piezo-composite ultrasound probe & high sensitivity receiver.

Advanced algorithms optimize performance for

differing operational situations

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Cygnus FMD System

The 3 main components of the system are the

• Subsea Electronics Module (Acetal or Stainless Steel)• Probe & Handler (Acetal or Stainless Steel) • CygFMD software

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Probe Handler

The innovative probe handler is self-aligning to ensure correct contact with the member it will align if brought to the surface at an angle of up to 20° in both planes

The 0.5MHz probe has a magnetic surface contact sensor which detects when it

has made contact with the test member surface sufficiently

As a safeguard, if the probe

loses contact during a test,

it will not be possible to

continue

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CygFMD SoftwareCygFMD is simple to use, with a green or red indicator for dry or flooded

Dry

Flooded

Typical A-Scan for a dry result

Typical A-Scan for a flooded result

Returning backwall echo

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The Cygnus FMD system uses an advanced intelligent algorithm which

employs a Fixed Gain Curve for minimum & maximum gain levels

Each FMD test performs 3 tests with minimum (cycle 1), medium (cycle 2)

& maximum (cycle 3) gains applied

It increases the gains as the member diameter increases, the wall thickness

increases & if there are higher levels of corrosion

A test piece is used to conduct a daily, function test prior to & throughout

the deployment ensuring the system is fully operational (logged in the

software)

Along with the innovative probe contact sensor & handler alignment this

ensures reliable, unambiguous tests results are easily achieved

Advantages over existing

acoustic FMD Equipment

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Multiple Gain for accuracy

Multiple test cycles are performed automatically at up to 3 Gain levels. The first test cycle starts with a Normal Gain level for the member diameter entered;

If a positive Flooded signal is detected on a member with low level corrosion on the back of the near wall, a Flooded result is returned - as no additional testing can alter this result

If a Dry result is detected the test is instantly repeated at an increased gain level. This ensures a member with internal corrosion is catered for as the ultrasound signal will need more gain. This process is repeated until either

(a) maximum gain has been reached or (b) a Flooded result has been found

Only when consecutive Dry results have been found will the FMD Test return a Dry result

This provides ultimate confidence in the result returned

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Multiple Gain Displayed

The A-Scan for each gain level can then be selected to view

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Conclusion

The intuitive operation, inbuilt system

checks & advanced functionality of the

Cygnus FMD system all mean the user

can have confidence in their

inspection results

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The Cygnus FMD system is available for hire through Ashtead Technology worldwide

Ashtead Technology have a large stock of all the parts for systems to be used on ROV’s & by divers