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Deep-Submergence Electrical Connectors For 4,500-Meter-Rated AUV

By Amy Brown



Six BIRNS Millennium flanged receptacles (FRs) with five 16-AWG pins and eight 20-AWG pins.


Subsea connector technology has advanced apace with the increase in the use of sophisticated new vehicles to explore the ocean. Connector systems for these innovative submersibles can now provide faster, more accurate communication, increased options in power and signal, and enhanced performance capabilities for sensors, cameras and sonar. As today’s underwater vehicles are also becoming more compact and powerful, so too are the connectors serving as conduits for their wide ranges of complex systems.

As an example of such synergy, BIRNS, Inc. (Oxnard, California) was asked by Bluefin Robotics (Quincy, Massachusetts) to develop 12 deep-submergence custom cable assemblies with BIRNS Millennium electrical connectors. The cable assemblies were for its new 4,500-meter-rated Bluefin-21 AUV. This Bluefin vehicle was custom configured for marine services contractor Phoenix International Holdings, Inc. (Largo, Maryland). Phoenix needed an air-shippable AUV with a small onboard footprint capable of seamless mobilization on vessels of opportunity. Delivered in 2013, the AUV provided highly accurate, high-resolution seafloor imagery for a range of Phoenix customer requirements, from subsea research and offshore applications to military and archaeological investigations. In late 2013, Phoenix used the AUV, called Artemis, on a successful mission to find a U.S. Air Force F-15 plane lost at a depth of 3,000 meters off the shore of Okinawa, Japan. The highly modular 17.2-foot-long vehicle weighed 1,600 pounds and was capable of reaching speeds greater than 4 knots. It could operate at 3 knots for approximately 20 hours with standard payload, and was equipped with field-swappable batteries and sophisticated survey acoustic and optical payloads for highly efficient operations and performance capabilities. Artemis was most recently deployed in the Indian Ocean in search for wreckage of Malaysian Airlines Flight MH370, which had 239 people on board when it went missing in March. Artemis was tasked with imaging a large, focused search area up to 5,000 meters deep.

Since the vehicle would be operating at depths of 4,500 meters up to 20 hours at a time in demanding operational conditions, the most rugged connectivity solutions were necessary. BIRNS created custom connectors and cable assemblies with 48-inch leads for a wide range of systems on the free-flooded design, whose titanium main electronics housing measured approximately 20 inches in outside diameter and approximately 16 inches in inside diameter, resulting in tight tolerances for its cable assemblies.


Functions met by the Connectors
Artemis used a variety of connectors in a range of pin and cable configurations. The most critical pieces of connector hardware are those installed in the Bluefin sphere. The connectors ranged in size from the BIRNS Millennium 3G to the 3O, with a variety of pin quantities and pin diameters, from 10 22-AWG conductors installed on 3G connectors to combinations of 16-AWG and 20-AWG pinouts in connector pairs of the 3M. The 3G size in particular was an enabling component in that it was highly compact. It had an electrical insulation diameter of 0.33 inches and tight tolerances between pins, with spacing of 0.08 inches center-to-center distance, and socket-to-socket clearance of only 0.02 inches. A slightly larger (0.46 inches) BIRNS Millennium 3K mating pair had 16-AWG conductors.

There were a total of six BIRNS Millennium 3M connector pairs throughout the pressure vessel. The BIRNS Millennium 3M connectors each had a 0.58-inch electrical insulation diameter and a flange dimension of 1.5 inches. The 3M connectors had five 16-AWG conductors and eight 20-AWG conductors. Two of the 3M cable assemblies were molded, and four were designed with pressure-balanced oil-filled (PBOF) cables with advanced oil-filled adapters incorporating double-ferrule hydraulic fittings. This system reduced the risk of cut tubing found with the use of hose clamps in PBOF assemblies. It included two small rings that together formed a gentle wedge. When pushed down by the main nut, the rings gently yet securely pressed against the tubing, which was supported internally with a stainless steel tube insert, in turn sealing and retaining it. A right-angle PBOF cable assembly with a mating pair of BIRNS Millennium 3O (0.70-inch electrical diameter) had 23 20-AWG conductors. To continue this article please click here.


Amy Brown is the director of corporate communications for BIRNS, Inc. and is responsible for developing and managing a comprehensive set of strategic external marketing, media relations and internal communications programs. Her career in marketing began in 1998, and she has held senior marketing management roles for companies in the marine industry since 2004.




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