Device Prevents Cable From Becoming Tangled With Buoy Lines

A costly tangle involving petroleum explorers and fishermen may soon come to an end, the American Petroleum Institute reports.

Mobil Oil Corporation has patented a device that will prevent seismic cables used for exploring beneath the marine bottom for oil and gas from becoming tangled with the buoy lines used to mark crab and lobster traps. Mobil has dedicated its patent for the device to the public so that it may be freely used by anyone without payment of royalties.

During marine operations, the cable containing the seismic instruments must be maintained at a designated depth. To do this, torpedo-shaped housings with movable wings are used. These depth control devices are known as hydroplanes or paravanes, and are commonly referred to as "birds." The birds are attached to the seismic cable, which is towed by an electronically equipped boat through the area being surveyed.

The seismic gear transmits signals which provide the information about the underlying strata.

Difficulties can arise if the wings of the birds, which are used to lower and raise the cable, come in contact with a lobster or crab trap line. The line can get caught in a space between the wing and the housing of the bird, and a sawing action may occur.

This action not only may damage the bird but also damage or destroy the trap.

The device that Mobil has invented to prevent this problem is a skeletal, frame-like structure which is fitted to the housing or the bird in front of each wing.

A trap line coming in contact with the frame simply slides away from the bird.

The API reports that Mobil has used the device successfully for more than a year, and is making its patent available to the public in hopes that others involved in offshore petroleum exploration will use the device in lobster and crab fishing areas.

Other stories from October 1977 issue


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