smart gauge plate

Pipeline & Gas Journal/August 2001/pipelineandgasjournalonline.com

The Development And Use Of SmartGauge Pigs In Offshore Applications

onsiderable time, effort andcost are used in recoveringgauge pigs from the subsea toinspect gauge plate conditions

prior to beginning hydrotest operations.Vessels used for pigging have to discon-nect, travel to the receiver and recover thegauge pig to deck for visual inspection.

The Copipe Arrival ConditionMonitoring Equipment (ACME, alsoreferred to as Smart Gauge plate; UK andinternational patents pending) provides ameans of determining the condition of apig-mounted gauge plate after a gaugingrun, without the need to retrieve the pigfor examination. ACME operates by usingelectrical circuits bonded to the gaugeplate to control the frequency of a signal-ing device. Gauge plate damage results incircuits being broken, which in turn caus-es a frequency change.

ACME offers significant project costsavings by reducing vessel movementsand intervention requirements and provid-ing a direct progression into hydrotestingif the gauge plate is acceptable (Fig. 1).

The ACME SystemACME is an add-on system for a stan-

dard gauging pig which enables the facil-ity to remotely determine the condition ofthe gauge plate on the pigs arrival in thepig receiver. This avoids the necessity torecover a gauge pig to determine the con-dition of its gauge plate, thereby savingsignificant vessel and intervention costswhen working at subsea levels.

ACME uses a standard aluminumpetalled gauge plate with a simple instru-

mentation adaptation to sense the platecondition. Prior to setting up the plate, aGo/No Go criterion is agreed, based onthe deflection of a bent peal relative to anundeflected petal (the usual condition foracceptance). Based upon this criterion, anelectrical break sensor detects any defor-mation beyond the agreed criterion.

The gauge plate sensor provides twopossible outputs:

Short circuitplate is within agreedGO condition; and

Open circuitplate is in NO GOcondition.

The output from the gauge platesensor is used on a pig receipt in thereceiver to switch the output of a pig-mounted pinger between two condi-tions to announce plate condition (thiscan be frequency, pulse pattern, on/off,etc., depending upon the applicationand other systems in use). The ACMEsignal is detected at the receiver, andthe gauge plate condition is broadcastfrom there, back to the launching endor another convenient location, usingeither the Pig Home system beacons,or a dedicated transmitter system.

Existing gauge plates may be easilyadapted to operate with ACME. A typicalplate arrangement is shown here:

An undamaged plate not only confirmsacceptable bore, allowing the pig to beremoved when more convenient, forexample at tie-in stage, but also allowshigh-pressure receivers to be used toallow immediate hydrotesting withoutvessel relocation, receiver removal andpig recovery.

If damage does occur to the plate,when the Copipe impact logger is used, itis possible to determine where the platebecame damaged, (which requires recov-ery of the pig). This can be used to ruleout the possibility of damage atlaunch/receive (Fig. 3).

Development And Testing ProgramA section of 16-inch pipe had been pro-

vided to Copipe as part of the preparatoryphase for the Draugen commissioningproject. This pipe was set up in Copipesyard between two coiled tubing reels. Onereel was used as an anchor and the winchon the second reel was used to pull pigsthrough the pipe sample (Fig. 4).

To provide a means of damaging thegauge pig, a threaded pin was fittedthrough the pipe wall at the midpoint ofthe pipe sample, in the 12 oclock position.This pin was inserted such that 40 mm ofprotrusion was caused. This was sufficientto ensure that the gauge plate would bedamaged, and is not the minimum damagethat the system can detect (Fig. 5).

By Les Graves and Tony Yates,Copipe Systems, Ltd., Aberdeen,Scotland

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5


plate. The pig used for the test was an IPP16-inch gauging pig of specific design forDraugen (Fig. 6).

The epoxy filling used to protect theelectrical components is extremely tough.Plates are hydrostatically tested to theirmaximum service pressure and water jet-ted to confirm the robustness of the plate.

The rectangular items around thewaist of the pig are pickup magnets forcollecting any metal objects from thepipeline, and are not a part of the ACMEsystem (Fig. 7).

The signaling device used in the testwas a dual-frequency acoustic pinger, setto operate in pulsed mode and to transmitaccording to the following convention: Gauge plate intact ......................30 KHzGauge plate damaged ................21 KHz

A standard pinger receiver with manu-

The pipe sample was cleaned bydrawing a utility brush pig through itthree times prior to the gauging trials.The pin was not fitted during this clean-ing operation.

The ACME system utilizes a gaugeplate that is modified by the addition ofelectrical sensors in a set of groovesmachined into the rear face of the plate.The location of the grooves relative to theouter edge of the gauge plate determinesthe sensitivity of the plate. The platesused in the trials had been constructed togive a sensitivity matching the value beingdefined by the Draugen project.

Visually, the ACME plates are almostindistinguishable from standard plates:only the connector for the electrical con-nection, and the epoxy potting protectionfor the electrical sensors distinguish the

al tuning was used to detect the outputfrom the pinger. In this mode of opera-tion, the gauge plate may be consideredas a switch, the function of which is tochange over the pinger frequency.

The acoustic antenna of the pingerwas arranged to protrude through thefront bulkhead of the pig, and can beseen in Figure 8 with the hauling loopremoved from the pig nose.

The test procedure was simply to insertthe pig into the pipe, and then pull it throughon the winch at approximately 0.5 meters persecond, stopping it at the far end of the pipe,and listening to the output frequency of thepinger to determine plate condition. Tworuns were carried out in this manner.

Outcome Of testsFigure 9 shows the pig about to be

PPSA Special Section

Figure 6

Figure 7

Figure 8


inserted, and the peg can also be seenat the top of the pipe. On both testruns, one plate petal was bent back byapproximately 15 mm.

Test TwoIn the second test, the pinger was

heard at 21 KHz after the pull through,confirming the successful function ofthe system.

Further TestsThe second successful test was repeat-

ed an additional six times. On each occa-sion, the system functioned perfectly.

The pig was also equipped with aCopipe impact logger, which is a smallcylindrical instrument approximately 50mm x 50 mm. This records any impactloading the pig experiences, and may beused to determine where gauge plate dam-age occurred. Both logs were identical.

The small events (approximately 10g)are the pig entering and leaving the pipe,and the much larger 20g event is the plate

being damaged. In a test of this type,where speeds are low, this impact resultsfrom the release of elastic energy in thepolyurethane of the pig as the pig ridesoff the obstruction.

The gauge plate damage was similar inboth tests. The plate from test two is shownin Figure 10. The mark where the pin struckthe plate can be clearly seen in this view.

Offshore UseSince the development tests, ACME has

been successfully used on a number ofNorth Sea and international projects.Diameters, lengths and water depths havevaried. Consistent success has created cus-tomer interest beyond expectation. P&GJ

Les Graves is operations director,Pipeline & Excavation Services, for CopipeSystems Ltd., which is part of PSL PipelineProcess Excavation in Aberdeen, Scotland.He has 26 years of experience in thepipeline industry, primarily offshore serv-ices. He has an MSC in EngineeringProject Management from LancasterUniversity. He is joint founder of CopipePipeline Services with Alan Evett.

ACKNOWLEDGMENT:The authors would like to acknowledge HalliburtonSubsea, EMC and Coflexip Stena Offshore Ltd.

Figure 9

Figure 10

Test OneIn the first test, the pinger was heard

at 30 KHz, despite the plate being obvi-ously damaged. On recovery of the pig,the electrical connector to the plate wasremoved and the pinger continued totransmit at 30 KHz. The pig was disman-tled. It was found that the nose connec-tor to the pinger was dislodged by theassembly method used, and was short-ing in its receptacle, thus causing the 30KHz signal. A new plate was fitted andtested fully, and the pig returned to thetest pipe.

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