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Seeing in the deep

Written by  John Sheehan Monday, 01 August 2016 00:00

Assessing the condition of pipelines, especially as they get older, is an increasing task. John Sheehan surveys potential solutions.

Tracerco’s Discovery tool. Image from Tracerco. 

The expansion of the offshore industry in recent decades has brought with it a huge growth in subsea pipeline infrastructure.

From the Åsgard Transport pipeline in the Norwegian North Sea to the West Natuna gas pipe line in the South China Sea, thousands of kilometers of offshore pipelines have been laid, all of which need regular inspection, repair and maintenance.

The focus on asset integrity management has also sharpened as operators look to increase the lifespan of mature assets.

Key to this are advances in both internal and external pipeline inspection technologies, which operators use to check for corrosion degradation and pipeline blockages.

Companies such as GE PII Pipeline Solutions, Rosen, TD Williamson and NDT Global among others are in the frontline in the battle against pipeline defects.

Halfwave

Smaller companies are also playing their part and Norway’s Halfwave has developed Artemis, a potential solution for operations in areas where the combination of deepwater and thick protective coatings rules out most traditional methods for non-intrusive pipeline inspection.

Based on acoustic resonance technology (ART) developed by DNV (now DNV GL) over the last 20 years, Artemis has been honed for inspection of rigid and flexible subsea pipelines.

The system is designed to check pipelines at depths up to 10,000ft, providing high resolution information by inspecting through coating materials and avoiding costly subsea mechanical intervention. The system clamps onto the pipe and provides real-time data to the topside inspection team. It is deployed by remotely operated vehicle (ROV) and performs a 360° scan using ART. The technology works with a sending transducer transmitting a broadband acoustic signal towards the pipeline. The signal spreads in the metal pipeline and a response is detected by a receiving transmitter, with the results then analyzed revealing resonance peak frequencies from which the structure’s thickness can be estimated.

The system can be launched from offshore installations using an inspection class ROV or from a vessel using a work class ROV.

Discovery

Another company providing clamp-on technology for pipeline inspection is Tracerco with its Discovery and Explorer offerings.

Discovery can perform a detailed high resolution CT scan of subsea pipelines, distinguishing between wax, hydrate, asphaltene or scale deposits, data that is paramount when planning any flow remediation campaigns. It can also detect wall thinning, corrosion and pitting.

Discovery is deployed using an ROV and clamped onto the pipe, with real-time communications allowing instant assessment of pipeline conditions.

Explorer meanwhile, can fast screen pipelines (100m/hr) to locate restrictions. Explorer detects the location of deposit build-ups by measuring the density profile of the pipeline and then analyzing any detected anomalies. An abnormal density, in relation to the material flowing in the line, indicates a build-up of deposit.

Both devices work without the need to remove the pipe coating material. Once Explorer has located the area of the suspected blockage, Discovery can be deployed to accurately characterize its precise nature.

The technology has recently been deployed to Australia, where there are more than 4000km of subsea pipelines in operation.

“Operators who face flow challenges need to get their pipelines back to full operation quickly,” says Ken Pearson, Tracerco’s managing director in Australasia. “The speed at which we can deploy, coupled with the fact that coatings do not need to be removed from the lines before inspection, saves time and costs whilst mitigating the risk of damage to the pipeline.”

Pigs get smarter

For internal inspection of pipelines, inline inspection tools, or smart pigging devices, are being used to help fight corrosion, cracking and blockages. The global inline inspection market is estimated to be worth about US$1 billion a year.

“A smart pig is a highly advanced piece of technology that we run inside a pipeline to inspect it,” explains Andrew Greig, operations engineer with pipeline operator Kinder Morgan. “Smart pigs have numerous sensors on them and inside them they have a computer and a hard drive that gathers data and stores it.

“Smart pigs use all sorts of highly advanced technologies, some similar to those used in a hospital like ultrasonics. Once we run the pig through the line we get a massive amount of data and we go through it and make sure we find all the critical areas and address them accordingly.”

Several runs are usually made in the pipeline, with a cleaning pig with brushes, magnets and scraper tools employed first to remove any debris from the pipe.

A geometry tool with caliper arms is used to check for any geometric faults such as dents that might be affecting the pipeline. The smart pig is then run to detect for any general thinning or corrosion in the pipeline.

The intelligent pigs are equipped with highly tuned sensors that can gauge the thickness of the pipes they are traveling through along with cracks, fissures, erosion and other problems that may affect the integrity of the pipeline.

The pigs, which are launched and recovered in the pipeline, collect data and transmit it to a team that interprets that data to gauge the health of the pipeline segments being scanned.

If any problems are found then teams not only know what the problem is thanks to a heavy set of data points, but know exactly where to go to replace the affected pipe thanks to highly tuned sensors.

Balltec goes flangeless

As the technology of the pigs themselves evolves, so too does the technology to launch and recover them. Balltec recently launched its flangeless pig launcher, which can be used in pipeline repair jobs.

“What Balltec has developed is a pig launcher that can be used in emergency situations or in adverse conditions where a section of pipe needs to be cut and that section of pipe then needs to be plugged,” Martyn Conroy, Balltec's VP of sales and marketing, told OE. “The pig launcher fits over the end of the open pipe and we have a pig that is held in a canister in the back of the tool and gripping mechanism that can grip hold of the pipe. Simple adjustments can be made to the gripping section to ensure that we can not only grip onto steel pipe, but we can accommodate any coatings that are on that pipe.”

Conroy said that the technology was developed when a client approached Balltec because they had an issue where a piece of pipe had been damaged during laying and they needed to cut out a section. In order to cut out the section they had to de-water that section as well.

“The end user was Total in the North Sea,” Conroy says. “Leading on from the back of that we were actually picked up by Statoil, which was doing some inspection, repair and maintenance work on the Åsgard Millom pipeline. They wanted to be able to use the pig launcher to inject a TD Williamson smart plug into the pipeline to plug a live pipeline.”

The existing technology was significantly re-designed to accommodate a larger smart plug of 4.5m in length with a mass of 1500kg. The plug launcher gripping mechanism was built to withstand pressure of up to 120 bar from within the pipeline.

“This is a unique piece of subsea equipment,” says Jon Jackson, Balltec engineering manager. “The subsea plug launcher is flangeless and allows the insertion of plugs without any existing infrastructure by gripping and sealing the end of a cut pipe. The plug can be launched via a simple hydraulic system and operated with minimum remotely operated vehicle intervention. This allowed our client to have no production loss during tie-in.”

The whole project was delivered to Technip and was successfully deployed and used in the Åsgard field in August 2015.

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