A new acoustic positioning technique to improve the quality and accuracy of pipeline touchdown monitoring has been successfully utilised by leading project management, engineering and construction company Technip. The company has installed a Sonardyne GyroUSBL transceiver on the stinger of its rigid pipe S-lay and heavy lift construction vessel, G1200. Used in conjunction with Sonardyne’s Ranger 2 USBL tracking system, the technology is used to acoustically track an ROV positioned at pipelay touchdown to ensure the pipe is being accurately laid in the permitted corridor.
Ranger 2 is a survey grade USBL acoustic positioning system designed for long range tracking of underwater targets and position referencing for dynamically positioned (DP) vessels. The system calculates the position of a subsea target by measuring the range and bearing from a vessel-mounted transceiver to an acoustic transponder fitted to the target. Typically the transceiver is deployed through the hull or over the side of the vessel; this enables targets to be tracked below, to the side and far behind. However on a large pipelay vessel, a transceiver cannot reliably ‘see’ through the thruster wash created at the rear. By fitting the transceiver on the end of the G1200’s pipelay stinger, it was positioned well away from thruster noise and in direct line of sight of the ROV behind it.
GyroUSBL combines a 6G high performance HPT transceiver with a Lodestar Attitude and Heading Reference/Inertial Navigation system in the same assembly. This combination eliminates alignment errors seen in conventional USBL systems and is proven to deliver unrivalled levels of accuracy and precision. It also means that users are now able to monitor the dynamic motion of the stinger’s tip.
“We’ve been incredibly impressed with the accuracy, precision and repeatability provided by Ranger 2 GyroUSBL. The success with the stinger-mounted transceiver means that we’re now looking to adopt this novel technique for future pipelay projects here in the Gulf of Mexico and elsewhere.”
“Typically, touchdown monitoring operations are conducted using an ROV deployed from a survey vessel following on behind the pipelay barge. With this new technique, the pipelay barge can use its own ROV to carry out the touchdown survey, therefore removing the need for a survey vessel altogether or allowing the survey vessel to get on with another operation, increasing project flexibility. “Locating a transceiver on the stinger is a great solution for ensuring that vessel noise disruption is rejected. The time-saving features of the pre-calibrated GyroUSBL also result in reduced operational costs with the ability for users to move it from vessel to vessel with minimal downtime whilst maintaining the highest levels of positioning performance.”
For more information about Lodestar GyroUSBL, click here.
For more information about Ranger 2, click here.