The INTERCON system was developed by Robert Hill, working in concert with Intercontinental Engineering-Manufacturing in Kansas City, MO, to provide a U.S. alternative to the ARTICOUPLE, and solve the issues present in the ARTUBAR design.
The operation of the system is straightforward. The system is a single degree of freedom connection that like other systems, establishes a transverse, fixed axis between the tug and barge, around which the vessels are allowed free relative rotation, or pitch. All other movements such as yaw, roll, and heave are restrained. Thus the tug heaves and rolls with the gentler motion of the barge, and unlike systems that allow motions in more than one axis, the system forces are predictable.
In the system, the port and starboard sides of the notch wall are fitted with a vertical channel member with the open side facing the barge centerline. Notches, or teeth are incorporated on the fore and aft sides of the channel to eliminate vertical travel. The channel sides are tapered to provide a wider opening to ease connection, and the side taper is flat enough to minimize resultant thrust from higher bow to stern loads imparted on the barge by the tug. The notches lie on the taper of the sides and are of equal angle, peaked to balance forces and to minimize multi-angle planes of contact when engaged by the tug's connecting helmet. The vertical extent of these connection ladders is determined by the relative draft range desired for operation, and they can be supplied in a skeg module, prefabricated for installation as a unit into the barge. The machined steel connecting heads of the tug--which are inserted into the channels port and starboard to make the connection--are configured to match the channel tooth pattern. Each head is mounted on a spherical support to allow auto-alignment to the channel while retaining the greatest load carrying capacity in a minimal space. The ram is a heavy fabricated steel cylinder supported on the O.D. by a bronze bushing. The bushings are mounted in the I.D. of a "Load Box" structure which is a stress-relieved steel fabrication designed to transfer all structural loading, shaped to suit the tug and pre-fabricated and outfitted at Intercon with full lighting, access, wiring, piping etc. for insertion into the tug as a module. To extend or retract the head, the rams are moved along the horizontal axis by a large, male threaded shaft turning in the female boss on the inside of the ram. The threaded shaft is operated by electric motors through gearing mounted to the housing. Two drive motors are provided - one for low-torque high speed operation, the second for high-torque low speed operation. Emergency drives are also available, for use in the event of an electrical power failure.
Like ARTICOUPLE, INTERCON allows connection at multiple drafts. No ballasting is required. The system also is part of a large manufacturers product line, and as such enjoys solid engineering and service support. There is a large population of the units in existence with long experience. The system is built in pre-fabricated hull modules for ease of installation. The system has ABS and USCG approval and certification for dual-mode service. The gear/screw drive, prevents accidental retraction at sea, and allows for finer control of the units. Only this system provides a positive means to prevent retraction at sea. The unit is designed as well, to a very high safety factor.
Addendum: INTERCON has released a new, lighter weight connection system. Based on the current design’s general principles, the INTERCON-C features a simpler drive, lighter components, and a lower price. The trade-off comes in component life over longer time periods for the same loading. This new unit will need shorter overhaul periods, but that is based on operation continually in heavy seas, which most times is not required.
Intercon has also introduced a “lightering” type system, which used teeth in a wave form, welded on the barge connection ladder, to match a similar wave-type helmet, allowing the helmet to be slightly withdrawn during loading of a barge or discharge at sea, to change draft while the tug remains at a constant draft.
As co-inventors of the system, OT&BE has designed many newbuild AT/B tugs with this system, as well as multiple conversions, all of which have been successful.