Miniature Sensors for Monitoring the Operational Conditions of Pipelines
Authors: Volk Michael , Miska S. , Freeman E. 
Published: April 2012

Abstract
A miniature sensing technology can be used inside pipeline maintenance pigs ofany size and configuration in order to measure fluid conditions, map pipelinefeatures, and identify potential wall buildup or defects. The miniature sensorcan be used in pipelines where conventional in-line-inspection tools cannottraverse, while significantly reducing deployment cost and risk. It can also beused to provide near real-time monitoring of critical pipeline characteristics. The pill-shaped housing containing the sensing elements can collect data onmultiple variables, including but not limited to, pressure, temperature, 3-axistilt, and acceleration. Multiple tests were conducted using the technologymounted onto pigs in a 12-inch flow loop with single-phase gas and liquidmedia. Results from the sensing device consistently identified known bends andwall-thickness changes as small as 0.125 inches. The sensor pill device wasalso deployed in a free-floating arrangement without a carrier pig in the flowloop filled with water. This design enabled the sensing device to travel thelength of the line without a pig, thus indicating a potential inspectionsolution for fully unpiggable pipelines.

Introduction
Subsea pipelines are difficult to access, costly to maintain, and areaccompanied with a high level of risk during most pigging and inspectionoperations. Furthermore, internal operational conditions often threaten thepipeline with corrosion, paraffin build-up, and hydrate formation. Externaldamage from ship anchors and seismic activity can also compromise the integrityof offshore pipelines. It is crucial that any pigging or inspection activitiesdo not disturb production from subsea pipelines, and provide the operator withsufficient information to gauge its integrity and condition. A miniature sensortechnology may provide a low risk solution by recording the conditions presentinside the pipeline, while using a minimal physical footprint. These rawmeasurements can be used to identify blockages within the pipeline and helpmonitor potentially hazardous situations.
By its very nature, it is difficult to know exactly what is going on inside, oreven outside, a pipeline. The consequences of not knowing, however, can becatastrophic. The technologies available to measure the precise location of apipe, the conditions inside it, and the integrity of the pipe structure itselfhave remarkably improved, alongside similar advances in instrumentation forinspecting, for example, the human body.
With advances in materials, electronics, and computers, medical devices aregetting smaller, faster, lighter, and more versatile. Lower costs have in manycases rendered inspection devices disposable. Smart sensors, which are createdby combining sensing materials with integrated circuitry [Schwiebert], arebeing developed for use in the biomedical industry. These smart sensors canmonitor physical, biological, and chemical reactions within the body. A singlesmart sensor pill could measure ECG (Electrocardiography), EEG(Electroencephalography), EMG (Electromyography), and/or heart rate. It is notuncommon to place multiple sensors on a single chip, with integrated circuitryof the chip controlling all of these sensors [Schwiebert]. Such sensorsgenerally have to be able to communicate with an external computer system tolog and record the transmitted data through a wireless interface. These sensorshave several other limitations as well, which include: limited on-board energystorage, biocompatibility issues, other safety issues, reliability, and issuesrelated to patient comfort.