Attempting to relocate underwater objects in a low-visibility environment can be a difficult and time-consuming task. Acoustic pingers and transponders solve this problem. Not long ago these devices were expensive pieces of equipment used primarily by the military, the oil and gas industry and oceanographic institutions. Today, these underwater locating beacons are being employed by a wide range of users including commercial diving companies, public safety dive teams, universities, environmentalists and companies in the energy industry.

One organisation employing these acoustic locators is EGS Asia in the Philippines. EGS is an international group of companies with offices in Europe, the Americas, Asia and Australia. It started in the near-shore environment doing port projects, reclamation work and pipeline laying. Today, EGS offers a broad range of technical services to the oil and gas, telecommunications and marine infrastructure markets.

As part of a recent project EGS Asia had to deploy an acoustic Doppler current profiler (ADCP), which is used to measure water current velocities over a depth range. To ensure the ADCP could be recovered when it was time to retrieve the stored data, EGS’s Roberto Ruiz attached a JW Fishers, USA, MFT-1 transponder. The transponder stays dormant, saving battery power, until activated by a gun-like device called an interrogator which causes it to begin transmitting an acoustic signal. The interrogator can be carried by a diver or deployed from a boat. Once the transponder begins sending a signal, the interrogator detects it and displays direction and distance to the target.

Ruiz reports: “We attach a MFT-1 to the tripod holding the ADCP before deployed in 15- to 35-metre water depth. Using the interrogator, the device can quickly be relocated and recovered.”

ASSIST

Ireland’s seabed territory is ten times larger than its landmass. The Ocean Science and Information Services Marine Institute was established to undertake and assist in marine research, to promote economic development, create employment opportunities and protect the ocean environment. The institute provides scientific and technical information that helps the country’s legislators make sound policy decisions to support and sustain Ireland’s valuable marine resource.

Routine monitoring and measuring of the ocean environment is essential to gather the data needed to provide the best advice. The work is carried out by a team of scientists and technicians which scrutinise any variations in marine chemistry or changes in the benthic environment. To ensure its oceanographic monitoring instruments can easily be recovered, the institute is using JW Fishers’ MFT-1 transponders and DHI-1 interrogator.

DESIGN

Helping to relocating underwater sites and oceanographic equipment is not the only use of these acoustic devices. Propipe in the United Kingdom is a leader in the design and manufacture of pipeline ‘pigs’ for the oil and gas industry. These pigs perform various maintenance operations inside the pipe, and ‘pigging’ is generally done without stopping the flow of material through the pipe. This is accomplished by inserting the pig into a ‘launching station’, an oversized section of the pipe that then narrows to the normal diameter. The pig is moved along by the pressure of the product moving through the pipeline, and is then removed at a receiving station, the ‘pig catcher’. To ensure the pig’s movement can be tracked, and its exact location determined should it become stuck, an acoustic pinger is attached. Propipe has acquired several of Fishers’ PR-1 pinger receivers so that it can track its pigs and be sure they are safely recovered.