Posted by: towmasters | March 7, 2010

Words Are Important: Stability, Lessons Learned, & Why We Need Better Stability Letters

Words matter. More specifically, the exact choice of words matter. English is a very complicated language, but one extremely rich in vocabulary, the benefit of which is that inter-personal communications (orders, requests, opinions, thoughts, recommendations or instructions) can be made very clear and precise if so desired. There’s usually no need for “kind of” or “sort of” when dealing with technical matters as long as you have a reasonable grasp of basic grammar and sufficient vocabulary at your command. This is important because…..

…..on February 18th the Coast Guard issued “lessons learned” notice #01-10, Towing Vessel Stability Requirements, which covers familiar ground: the dangers of ignoring two of the most important (and basic) instructions contained in every stability letter, that being to keep any between-tank crossover valves closed when underway and to avoid attempting to correct a list before the exact cause of said list is known. Quoting the report, The Coast Guard strongly reminds vessel owners and operators to ensure that all deck officers and engineers are fully apprised of the vessel’s stability letter requirements and that the vessel is operated in compliance with those requirements at all times.”

This, of course, is good advice, and I believe that the Coast Guard is sincere in wanting to see stability letter compliance improve. The tug Valour, the inspiration for this lessons-learned notice, went down unnecessarily and mariners died because of a combination of ignorance of basic stability procedures and blatantly routine violations of the stability letter by even the senior-most members of the crew. This behavior on the Valour was by no means an anomaly, and in fact could accurately be described as typical industry-wide, although mariners may now be slowly waking up to the risks. But simple as it may seem at first, there’s still more to it than that. Even if you are motivated to learn and do as much as you can to improve, after you read the typical generic towing vessel stability letter, and attempt to carefully follow it as you’re required to do, you realize that often this is flat-out impossible. These letters either have information gaps, don’t conform to the actual vessel, or both. Worse, they fail to take into account reality when it comes to the practical usage of tanks aboard a working tug.

My vessel’s stability letter says very explicitly that I’m allowed “no more than one centerline tanks or P/S tank pair of potable water, fuel oil storage, lube oil, and ballast water may be partially filled at any one time.” It also says that “trim should be minimized.” Wonderful! Now I’d like some stability guru to explain exactly how this vessel can simultaneously be effectively operated  while also complying with such a letter. Well, there’s no need, really, because it can’t be done. Not because the vessel is unsafe or unstable, but rather because the stability letter simply doesn’t fit the boat, and you’d be very hard pressed to find many that do. We have seven fuel storage tanks in total: three forward (#1-P, #1-S & #1-C), one amidships (#2-C), and three aft (#3-P, #3-S & #3-C). It is physically impossible to comply with both the stability letter’s slack-tank requirements and the legal  (and practical) requirement to minimize trim at the same time: it’s either one or the other, but you can’t have it both ways as written.

Out of necessity we’ve adapted a technically non-compliant but practical work-around that I believe nonetheless complies with the intent and spirit of the letter, if not the exact words. We utilize the otherwise-unused slack-tank allowance for the forward port & stbd. ballast tanks, which are left empty, and “loan” it to the fuel tanks, thereby allowing us to use the forward and aft fuel tanks simultaneously in various combinations to keep the vessel trimmed as we burn off fuel and our draft decreases. As long as we never have those ballast tanks in a slack condition we won’t exceed our total allowable number of slack tanks. Of course it’s only “technically” non-compliant because the stability letter wasn’t realistic, or even correct, in the first place. But wait, there’s more!

My vessel also has three relatively small clean oil tanks (port-lube, stbd.-gear and center-hydraulic, with maximum capacities of 661, 661, & 492 gallons respectively) that are integral to the #3-C aft fuel oil storage tank, which itself has a maximum capacity of 14,840 gallons. Our letter refers only to the lube oil tank, making no mention whatsoever of the gear and hydraulic oil tanks. In any case, assuming (which can be dangerous) for the moment that it was the intent of the stability letter’s author that all three can be treated as if they were lube oil tanks, I’d still be limited to using either hydraulic oil (from the center tank) or lube and gear oil (from the port & stbd. tanks) at any given time. We certainly would be severely limited in what we could do if that were the case. If in fact the volume, weight and free-surface of the oil in those tanks is insignificant to the vessel’s overall stability, as logic leads me to believe, then it should be duly noted in the stability letter that they’re exempt from consideration and may be used as needed in whatever configuration our oil needs dictate. If that assumption is incorrect then they never should have been approved in the first place.

We also have centerline tanks for slop oil and dirty bilge water, but no mention is made of either one of them in the letter. The port/stbd. pair of fuel oil “day” tanks also are omitted. Each of them have a maximum capacity of 3,400 gallons, a considerable amount, and they could easily be considered (mistakenly) as subject to the overall slack-tank allowance. How do you comply with a stability letter like that?. Well, like they say up in Maine, “you can’t get there from here.” The only logical response is a big WTF? and just do the best you can.

Shortly after I began writing about the sinking of the Valour and the associated stability issues I contacted a senior engineer at ABS about the wording of our letter and all letters in general. I remarked that my informal research indicated that misconceptions and confusion about how to comply with stability letters were quite widespread in the towing industry, though this is a separate problem from willful ignorance or disregard. I mentioned the potentially-confusing wording, the omitting of the day tanks, and my theory that they (and other unlisted tanks) might inadvertently work there way into a slack-tank allowance calculation and cause more confusion. He acknowledged this and stated that they had specifically begun using the wording “fuel oil storage” tanks to help avoid this problem. I felt that there was still room for improvement, and said as much, specifically recommending the additional wording of “fuel oil day tanks do not count towards the overall slack-tank allowance” as just one example. Whether or not this was given serious consideration, let alone acted upon, I do not know.

In the meantime it’s good to see the Coast Guard show continued interest in this long-overlooked area, as evidenced by the new “lessons learned” report. The truth is that most items on stability letters are easily complied with if the boat isn’t a wreck and it’s really just a matter of getting mariners to understand what can go wrong and what’s at stake when you blow it off.  Judging by how many times the Valour casualty report has been downloaded  from this site alone the interest from mariners seems to be quite high, which should give the Coast Guard reason to believe that their efforts have not been wasted and are, in fact, slowly bearing fruit. As of this writing the Tug Valour Investigation Report post (and hopefully the report itself) has been read 832 times since it was published here in September 2008, the very first month of this blog’s existence. I once again want to thank and congratulate Lt. Cdr. Charles Barbee, the report’s author, for providing a clear, well-written account and analysis of the events which takes a tragedy and turns it into what may eventually prove to be one of the most valuable towing vessel safety lessons that has ever been issued by the Coast Guard. It is a benchmark that will be hard to beat. The related posts Close The Crossovers!, Your Stability Letter: Read It & Heed It, Practical Stability For Tugs and Damaged Stability For Barges have been read 222, 325, 316 and 522 times, respectively, since their publication in January 2009.

But it’s not enough to simply proclaim that the licensed officers, deck and engineering alike, must heed the stability letters issued to their vessels, because instructions that aren’t understood, or understandable, are useless. Instructions that are incomplete, contradictory, or impossible to follow are just as useless and possibly also dangerous, especially when inexperienced, untrained or incompetent personnel are left to their own devices.  Letters should have no information gaps (translation: include all tanks or usable voids by name/number and specify whether they count or not) so that mariners don’t have to make potentially-wrong assumptions as to what is the correct way to comply or action to take. If the Coast Guard, ABS and the Towing Safety Advisory Committee really want to do something substantial to help improve stability letter knowledge and compliance then a good place to start is with the language used in them. The best choice of language eliminates confusion, removes doubt, and does away with the need to try and interpret what the marine architect or engineer “meant.” The best choice of language is ultimately determined not by what an author personally thinks is adequate, or what “should be” if we were all graduates of the Webb Institute, but by the needs of the audience that’s attempting to be reached. When in Rome…..

The MTVA stands ready to assist them in this plain-language effort should they choose to act and are willing to work with us. If not, the best advice we can offer to towing vessel officers is to read your specific vessel’s stability letter and then, if after giving it all due consideration you conclude that it is an appropriate way of dealing with a very imperfect situation, consider using the principles mentioned above and in the post Practical Stability For Tugs.

Legal Disclaimer & Warning: I absolutely detest the legal-weenie bullshit, but I must give readers fair warning. Your stability letter (faulty though it may be) is an instruction document to the master that legally requires strict compliance, so you creatively interpret it (as I do) or ignore it at your legal and/or physical peril. Be aware that you can be held liable for failing to comply with any part of it for any reason at all, including a very good reason such as that full compliance would require that the boat be driven around in an extreme state of trim and handling like shit. That’s just the paper-driven world we live in…..



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