Posted by Sonardyne Asia Pte Ltd on 06/26/2017

Acoustically-aided system improves subsea inspection efficiency

Acoustically-aided system improves subsea inspection efficiency

Huge potential for fast-working, high speed ROV

New subsea technology developed by innovations-focused partners in Sweden and Norway could have game-changing potential for maritime organisations seeking faster and more accurate high-resolution marine surveys.

A new high-speed survey remotely operated vehicle (SROV),Surveyor Interceptor, has been specially designed to improve the speed, precision and efficiency of seabed mapping and pipeline inspection surveys. The vehicle’s revolutionary design includes a hydrodynamic hull and powerful drive train which provide the propulsion for the SROV to travel at speeds up to six knots – almost 50 per cent faster than conventional work class ROVs.

To enable ROVs to travel at faster speeds close to the seafloor or alongside offshore oil and gas pipelines, the vehicle’s manoeuvring and propulsion systems need to receive very precise and uninterrupted position updates. So the SROV developers installed a cutting-edge acoustically-aided inertial navigation system created for subsea vehicles by Sonardyne International, a subsea instrumentation manufacturer specialising in acoustics for underwater navigation, positioning, data communications and control.

Sonardyne’s inertial navigation system, SPRINT, makes optimal use of acoustic aiding data from acoustic ultra short baseline (USBL) and long baseline (LBL) positioning technologies together with Doppler Velocity Log (DVL) sensors and other pressure sensors. This improves position, accuracy, precision, reliability and integrity in any water depth while also reducing the time taken to complete tasks which reduces ROV costs. The accuracy and precision provided by the advanced inertial navigation technology complements the SROV’s state-of-the-art imaging and mapping sensors which, during successful offshore integration trials, resulted in improved data quality while also substantially reducing the ‘cost per kilometre’ of subsea surveys.

Inertial navigation systems (INS) use a computer, motion sensors (accelerometers) and rotation sensors (gyroscopes) to continuously calculate the position, orientation, direction and speed of a moving object without support from external references. According to Sonardyne, inertial navigation is inherently self-contained and robust with very good short-term accuracy. However, it can drift over time.

To get round this problem, SPRINT is supported by complementary positioning data which provides long-term accuracy, robust performance and greater vehicle control. With theSurveyor Interceptor, an inverted USBL transceiver has been interfaced directly to the acoustically-aided inertial navigation system to provide a “highly optimised navigation solution” that delivers position updates up to 100 times each second.

The 2,000 metre (6,560 feet) ratedSurveyor Interceptoris the product of a combined venture involving MMT of Sweden, which specialises in high resolution marine surveys, Norwegian company Reach Subsea, an international subsea service provider, and Norwegian ROV manufacturer Kystdesign.

“We were looking for an inertial navigation solution that would deliver real-time performance with high speed updates,” says Jonas Andersson, research and development manager at MMT. “By running Sonardyne’s SPRINT inertial navigation system we witnessed a marked difference in the accuracy of all ROV positioning activities during the period, which in turn made a marked difference to the quality of the survey data received.”

Following successful trials,Surveyor Interceptorhas recently completed its first commercial assignment, inspecting the 106 kilometre (65 miles) Knarr gas pipeline in the North Sea at depths ranging between 140 and 400 metres (460 and over 1,300 feet) for Gassco, operator of the gas transport system which delivers Norwegian gas to continental Europe and the UK through more than 8,000 kilometres (4,970 miles).

Sonardyne

The new SROV operates at speeds 50 per cent faster than conventional work class ROVs.

SONARDYNE

The high speed SROV was used to check the external condition of the new pipeline and rock berm protection before gas was pumped through the pipeline. The inspection took just 17 hours at an average speed of 6.2 kilometres an hour – almost three times faster than a conventional ROV would have taken to complete the task.“Most of the gas pipelines lie on the seabed, and ROVs controlled from surface vessels must therefore be used for maintenance and monitoring work,” says Kristin Kinn Kaste, vice president for the transport network. “Such operations are basically expensive. Factors affecting the price include the offshore vessel, the ROV’s efficiency and the choice of inspection technology. Using new, world-leading technology is therefore cost-efficient for us.”

Alan Macdonald, sales manager for Sonardyne, adds: “At a time when the offshore industry is focused on ways to reduce costs without compromising on quality, the combination of MMT’s ground-breaking ROV and SPRINT represents a unique offering to the construction survey marketplace.”


Sources:

http://reachsubsea.com/assets/surveyor/

http://www.cadden.fr/sites/default/files/pdf/Sprint.pdf

http://www.gassco.no/en/media/news-archive/Innovative-ROV-on-test1/

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