Wear and tear, and corrosion, they get everything eventually. That is why the regulations require equipment inspections, especially of critical items whose failure could be catastrophic. One area that is of particular concern to towing vessel mariners is the towing assembly: that is, the tug’s towing winch, tow wire, and the poured socket at it’s end, as well as the pennant wire or shock-line, surge chain, towing plate, bridles, and padeyes belonging to the barge you’re going to tow. Most importantly, the various shackles, detachable links and associated hardware (nuts, bolts, lock-washers, cotter pins, etc.) that hold it all together must be given a careful look too. The towing assembly, alternatively, also includes all of the lines, wires and assorted hardware used in towing alongside and pushing. The required pre-voyage inspections (33 CFR § 164.80) cover all of these items, as well as navigation safety equipment aboard the tug or towboat.
My regularly-scheduled inspection of the towing assembly of the barge we normally tow, as opposed to and conducted apart from the required pre-voyage inspections, revealed a level of wear on some of the components that had reached the point that it warranted their replacement, so out came the cutting torch and the sledge hammers. The three stud-link chain links at the ends of the surge chain and bridle legs that connected to the shackles at the towing plate had significant wear on two or three different planes: on one or both faces (where they rub up against the inside of the shackle jaws) and in the grip (where they rub against the shackle pins), so we cut them off. The next links in line were in good condition and had little wear, so they’d be fine for some time to come.
The bows of the shackles where they chafed against the inside of the towing plate’s eyes had lost some metal…..
…..as had the inside faces of the shackle jaws (from the opposing faces of the chain links)…..
…..and the pins that secure them, rubbed continuously by the grip-area of the chain links.
Here are two views showing exactly where the multiple points of contact are and how the wear occurs simultaneously on the shackle pin, the inside faces of the shackle jaws, and on the opposing faces and grip-area of the chain links…..
…..and the multiple planes of wear at one spot in the grip and face areas of the chain links.
The eyes of the towing plate had worn too, mostly in the forward eye where the surge chain attaches, but it was still well within accepted tolerances.