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Marine Electronics


December 2011 Issue

OSIL Designs ROV-Triggered Sampling System
Ocean Scientific International Ltd. (OSIL), based in Havant, England, supplied in October a water sampling system to an oil major for use in offshore operations off the West African coast.

The oil major had several requirements for the system. It had to be capable of retrieving multiple samples and have space for a CTD probe or similar instrument. The system also had to be fitted to and operated by an ROV under difficult conditions. The samples were to be collected at fixed depth and had to be collected in conjunction with other ROV samples. This prevented the use of traditional wire water sample collection methods, due to the risk of entanglements.

OSIL designed a sampling system that uses six primed five-liter Niskin bottles, which the company said were chosen due to their robustness, with space for an AML Oceanographic (Sidney, Canada) CTD Plus V2 in the center of a stainless steel frame. The frame could then be mounted to the ROV. The system is being used off the coast of Nigeria in the exploration for offshore oil, OSIL said. For more information, visit www.osil.co.uk.

r-tTS Monitors Mooring Chain Tension in Real Time
WFS Subsea (Aberdeen, Scotland) and Monitor Systems Scotland Ltd. (Aberdeen) have developed a tension sensor for real-time wireless load monitoring, the companies announced in October.

The Real-Time Tension Sensor (r-tTs) is a PC-based wireless anchor and hawser system from Monitor Systems that uses WFS wireless capability. It provides real-time data on mooring chain tensions for all types of production vessels, including FPSOs, and can also be used to monitor loads on renewable energy devices, such as floating wind turbines and wave riding devices, the companies said.

Typically, once an alarm is received to indicate a problem with chains on a production vessel, it's too late. The r-tTs provides immediate data on load, tension, inclination, orientation and can be used to effectively monitor subsea mooring lines, anchors and chains.

The r-tTs uses hybrid radio/acoustic technology to monitor multiple chains simultaneously and give early indication if safe load parameters are exceeded. Data transmission is unaffected by shallow and congested waters, harsh weather conditions or ambient noise, allowing the r-tTs to operate in complex environments and making it a complimentary device where acoustic methods are already being used. For more information, visit www.wfs-tech.com.

WASSP Multibeam Locates MV Rena's Containers
A WASSP Ltd. (Auckland, New Zealand) multibeam sonar was recently used by hydrographic surveyors to locate lost containers at the grounding of the 236-meter cargo vessel MV Rena on the Astrolabe Reef off the coast of New Zealand.

Within 48 hours after arriving in Tauranga, New Zealand, the multibeam had been used to identify 12 targets, WASSP said in November. Seven of these targets were submerged containers at depths of up to 80 meters.

Single-beam echosounders and side scan sonar have been used to support the salvage operation, however, multibeam echosounding systems provide a more economic means of gathering seabed information, particularly in deeper waters, WASSP said.

The surveyors involved in the salvage effort said they were surprised how quickly they were able to get the equipment fitted and the system up and running. Most multibeam systems require significantly longer mobilization time frames, the company said.

"In relation to the Rena salvage, WASSP provides a means of covering a lot of seabed very quickly, which is crucial in a salvage operation," WASSP General Manager Ian McDonald said. For more information, visit www.wassp.com.

Pressure-Inverted Echosounder Deployed off Hawaii
Sonardyne International Ltd. (Yateley, England) has deployed its first Pressure-Inverted Echo Sounder (PIES), a long-life sensor logging node designed to measure the average sound velocity through a column of water from the seabed to the sea surface, the company announced in November.

Deployed off the coast of Hawaii, the PIES gathers information that will help oceanographers to better understand ocean and atmosphere-ocean coupling dynamics.

Pressure-inverted echosounding works by transmitting an acoustic pulse from a PIES instrument on the seabed upward. The pulse is reflected off the water-air boundary at the sea surface and returns back to the seabed, where it is detected by the PIES. This enables a measurement of the two-way signal travel time to be calculated. At the same time, a precise internal pressure sensor takes a depth measurement. Average water column velocity can then be calculated from the depth (i.e., distance) and travel time data.

Depending on the sampling interval configured, the PIES can stay on the seabed for up to five years, Sonardyne said. The unit, located at a depth of 950 meters in a water channel between the islands of Hawaii and Maui, is logging an average sound speed reading every seven minutes.

Data gathered from the Hawaii survey will be recovered at the end of the mission, the company said. Sonardyne engineers will return to the site in a few months and will acoustically command the PIES unit to disconnect itself from its tripod stand. After the PIES returns to the surface under its own buoyancy, scientists will recover the unit and download data for analysis. For more information, visit www.sonardyne.com.

Cable to be Among First in Caribbean to Offer 40G
TE SubCom (Morristown, New Jersey) and Columbus Networks (Bridgetown, Barbados) have partnered in the deployment of a 40G upgrade to the CFX-1 undersea cable system, which connects the U.S. to Colombia.

The upgrade, which the companies said was to be completed in November, will allow for an increase in the CFX-1 system's final design capacity to 2.5 terabytes per second per fiber pair. The upgrade will make the system among the first in the Caribbean to offer 40G service.

CFX-1, which was constructed by TE SubCom and entered service in 2008, has landings in the U.S. and Colombia, with a branch to Morant Point, Jamaica. The 2,500-kilometer undersea system was originally designed for a transmission of 10 gigabytes per second transmission. For more information, visit www.subcom.com.


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