Revisiting the tragic loss of Maritrans’ tug Valour for some lessons-learned type discussion will be a recurring project here on the MTVA Forum. For now, here’s two of the more important points that can be immediately drawn from it:
1. Stability letters for towing vessels are either widely misunderstood, widely ignored, or some combination of the two. Nevertheless, the Master is required to understand and abide by the conditions stated on the stability letter at all times.
2. It therefore follows that the practice of leaving open the cross-over valves between the various fuel, water and ballast tanks is both potentially quite dangerous and far too common.
I believe that stability knowledge amongst towing vessel officers is generally well short of where it should be. This has been a subject area and practical discipline in which I had always assumed that the unlimited-tonnage officers had an enormous edge over us small-craft jockeys, but a ship captain recently disabused me of that idea. Nevertheless, most trouble can be avoided on tugs even without having a full grasp of all the physics behind the phenomenon of free-surface effect, the righting arm, metacentric height, etcetera.
The focus of this post is on the dangers of leaving cross-over valves open, whether at sea or not. In short, keep your cross-overs closed at all times unless you need them open temporarily while loading fuel oil and water. If you need to occasionally level your tanks between fill-ups to correct a list, only open them for long enough to accomplish the task, then close them again, and avoid doing this at sea if at all possible. Keeping the valves closed also helps protect your damaged stability, as well as your intact stability. You could be struck and holed by another vessel while tied to a dock or at anchor. If the cross-overs are left open, and this fact is forgotten in the heat of responding to the emergency or the valves become inaccessible because of flooding, it’s possible to wind up sinking because of it, right there at the dock.
Just keep ’em closed and you have one less thing to worry about. How hard can it be?
Also see the posts Tug Valour Investigation Report, Your Stability Letter: Read It & Heed It, Practical Stability For Tugs and Damaged Stability For Barges for more on this subject.
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