The original ATB vs. ITB post, from November 2008, was due for a major updating, including lots of photos, so here it is.
Warning: before you read any further , please be advised that these are my definitions and opinions. Others, including but not limited to the U.S. Coast Guard, naval architects and some of my fellow mariners, may disagree. C’est la vie. In any case, I get asked this question often and what follows is my standard answer: “Within the rather broad category known as towing vessels there exists a sub-category known as ATB’s, which stands for Articulated Tug & Barge. There is another sub-category known as an ITB, or Integrated Tug & Barge. They are not, and never were, the same. Nor are either of them, with some limited exceptions, a real tug in anything but name.” This answer, I believe, is based on sound logic and reasoning, not regulatory doublespeak or wishful thinking.
Moving right along, this is an ITB…..
…..which, as you can plainly see…..
…..is no tug…..
…..not even a little bit, except for having propellers.
Even at their peak of popularity there were very few ITB’s in existence, so many of you might never have seen one. They bear no relation whatsoever to a real towing vessel. They were designed from the keel up as nothing more than regulation-beaters, capitalizing on the uninspected vessel-status of towing vessels to get away with lower manning, construction and operational-safety standards. They’re simply small to mid-sized tankers with detachable propulsion/control units that are rigidly connected and do not move independently. An ITB “tug” disconnected from its “barge” is a sight to behold: unstable in anything but the calm waters of a well-protected harbor, and having the ability to do absolutely nothing remotely tug-like besides moving about under its own power. Click here for more photos and some history.
An ATB, on the other hand, is a different story. There are two basic types of them, purpose-built (new) and converted, and they presently use one of six connection systems: Articouple, Bludworth-Cook, Hydraconn, Intercon, JAK and Westec. The generally-accepted slang term for them is pin boats, the reason for which should be obvious. When “pinned in” to their barges an ATB pivots on the transverse axis provided by said pins, allowing the “tug” to pitch independently from the barge, but they roll as one.
The purpose-built type are generally not very seaworthy when disconnected and outside of the notch in open or exposed waters, although some people might try to bullshit to the contrary, and even in protected waters they’re very limited in what they can do. For the most part, unless there’s another compatible barge around for them to move, they’re pretty much useless as a tug. The idea of getting out of the notch at sea, in anything but calm to near-calm wave/swell conditions, and taking the barge in tow the old-school way is sheer lunacy. Unless they’re pre-rigged to an emergency hawser and can just back out of the notch and roll around on the barge it isn’t going to happen. Furthermore, you wouldn’t want to be up in that high wheelhouse getting whipped around by the seas without the strong stabilizing influence of the barge. The probability of seriously injuring or even killing someone while attempting this maneuver would be unacceptably high. Suffice it to say that you just don’t ever get out of the notch on purpose unless you’re in port. Unintended/unexpected pin retractions at sea in bad weather have occurred on the West Coast and I understand that they were pretty ugly.
To illustrate the modern, purpose-built type, here’s Reinauer Transportation Co.’s ATB Meredith C. Reinauer…..
…..and the Vane Brothers ATB Brandywine…..
…..and Moran Towing Co.’s ATB Linda Moran.