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Alum MSD Tank R/R/coating? (Peggy?)
Im assisting a friend whose correcting survey deficiencies abd his
purchased motorsailer. Among the usual long list of such items is a 45 gal Al MSD (holding) tank nicely custom-fabbed & fit by a former owner (why Al??arrggghh) to perfectly fit its turn-of the-bilge space. Tank is also parellelogram in plan, i.e. any reasonably avail polymer tank which may fit the space will be of lower capacity. Tank has a small lkg IWO a vent o-let, and a 10" handhole. Owner's yard had ordered a new bladder which I'd dissuaded him from following through with (thank for your years of debunking them & correcting me then too Peggyg), but R/R time window is short (5 days). Al tank will be pried out of its foamed-in place position via the usual Chinese firedrill that requires in AM, & taken ashore. We are contemplating the *option* of cleaning the tank, assessing its condition, and if not significantly wasted, welding and/or doubling the leak, blasting or otherwise prepping it's insides, and coating it with an appropriate epoxy or other suitable coating in order to exend its service. Experienced or hands-on guidance re a specific coating and/or other repair & protection option I may not have considered? Much TIA, Frank |
wrote:
Tank is also parellelogram in plan, i.e. any reasonably avail polymer tank which may fit the space will be of lower capacity. Not necessarily. Assuming that you're in the US, check Ronco Plastics (http://www.ronco-plastics.com)...they have more than 400 stock molds, over 100 of which are non-recectangular. Tank has a small lkg IWO a vent o-let, A what???? but R/R time window is short (5 days). Hey...lack of planning on his part doesn't necessarily create an emergency on anyone else's part! :) Al tank will be pried out of its foamed-in place position via the usual Chinese firedrill that requires in AM, & taken ashore. We are contemplating the *option* of cleaning the tank, assessing its condition... A waste of time...'cuz if it's leaking anywhere, what you're gonna find is a tank that's a about to spring a bunch more leaks. and if not significantly wasted, welding and/or doubling the leak, blasting or otherwise prepping it's insides, and coating it with an appropriate epoxy or other suitable coating in order to exend its service. Not worth the effort. My advice: Slap some Marine Tex on the existing leak--it won't hold permanently, but it will for a few weeks--to get through the impending "emergency"...then take the time to find a fit a replacement tank. 'Cuz to do it right is gonna require new hoses and at least some investigation into plumbing mods. Plan B: Go ahead and pull the tank out--but if you do, just take it straight to the dumpster. Put a portapotty onboard to keep him legal till he can take the time to do it right...'cuz there's a lot of truth in old adage, "do it right the first time, or expect to do it over." -- Peggie ---------- Peggie Hall Specializing in marine sanitation since 1987 Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and Other Sources of Aggravation and Odor" http://www.seaworthy.com/store/custo...40&cat=6&page= |
Peggie Hall wrote:
Tank has a small lkg IWO a vent o-let, A what???? :-) A weld-o-let being a welded tank outlet fitting, the weld-o-let serving the vent (a vent o-let, you no lika da contractionG?). but R/R time window is short (5 days). Hey...lack of planning on his part doesn't necessarily create an emergency on anyone else's part! :) Very grateful your expert input, Peggy. Jovially consider that none of it is new, and particularly that not all, or even most, emergent short repair windows are the consequence of poor planning. Without unnecessary elaboration, we have several tentative interim repair options to weigh. My UT's of the tank earlier (now yesterday) fail to find evidence of generalized deep pitting or widespread wastage (IWO of what areas may be UT'd in situ), dictating further inspection before any conclusion may be drawn (even though we'd both expect it to be quite deteriorated otherwise if it had been used much - it wasn't). It's also the general order of the day for weld-o-let welds to locally pit or waste faster in typical tanks & pressure vessels. I'm seeking a coating recommendation involving a product more readily found around the boating scene, as simply one part of only one option that is not yet ruled out. Were I in a commercial yard husbanding a chemical tanker, I would know exactly what to have applied & how, but such coatings are not packaged in tiny cans for boater use. I could have an industrial marine coating saleman send me a free sample that would be perfect, but the critical path timeline will not permit this. Gently, while I cannot knowledgeably speak in terms of the boating world and its ways, even as a part-time boater myself, this sort of thing arises & is dealt with on a daily (and nightly) basis in ship repair and is the rule more than the exception. We learn to think outside the box for very surival, and emergent deadlines are serious (though we ourselves try not to be), not symptoms of poor planning or laziness, but the opposite and demanding seasoned innovation. So this is why I have posted and what I seek. :-) The Owner & I have a combined 80 years of responsible ship repair background, Peggy. Relax a little. It's true that a rush delivery of a new tank of approximate & workable dimensions may be possible and that is already concurrently pursued; we may be old but we ain't dead yet. But I'm not looking for a coating option for plastic. 8-^) Well, yet. :-) In any case I disagree that the old tank, even if found to be beyond interim repair, should be thrown into a dumpster right after removal. As related, it has been carefully fabricated for best & fullest fit. It will be measured & drawn for eventually fabbing a 316L tank at convenience as the Owner's preferred future installation. Someone did an outstanding job of fabbing a small tank from the wrong material; we don't throw away the good part of another's effort with the bad of their ignorance. Instead, we come up with the best interim fix we can, and then do the job *really* right. We don't regard epoxy putty (Marine-Tex) as an interim shoreside repair of any metal tank, either, but a voyage one. But I do have a sense of humor on USENET. :-) Thank you again for your comments & time. BstRgds, Frank Al tank will be pried out of its foamed-in place position via the usual Chinese firedrill that requires in AM, & taken ashore. We are contemplating the *option* of cleaning the tank, assessing its condition... A waste of time...'cuz if it's leaking anywhere, what you're gonna find is a tank that's a about to spring a bunch more leaks. and if not significantly wasted, welding and/or doubling the leak, blasting or otherwise prepping it's insides, and coating it with an appropriate epoxy or other suitable coating in order to exend its service. Not worth the effort. My advice: Slap some Marine Tex on the existing leak--it won't hold permanently, but it will for a few weeks--to get through the impending "emergency"...then take the time to find a fit a replacement tank. 'Cuz to do it right is gonna require new hoses and at least some investigation into plumbing mods. Plan B: Go ahead and pull the tank out--but if you do, just take it straight to the dumpster. Put a portapotty onboard to keep him legal till he can take the time to do it right...'cuz there's a lot of truth in old adage, "do it right the first time, or expect to do it over." -- Peggie ---------- Peggie Hall Specializing in marine sanitation since 1987 Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and Other Sources of Aggravation and Odor" http://www.seaworthy.com/store/custo...40&cat=6&page= |
IMO, any efforts to salvage a leaking metal waste tank is wasted
effort...only briefly delaying the inevitable..'cuz the first leak is always just the FIRST leak. For the short term, patching a leak with Marine Tex accomplishes as much as anything else. My UT's of the tank earlier (now yesterday) fail to find evidence of generalized deep pitting or widespread wastage (IWO of what areas may be UT'd in situ), dictating further inspection before any conclusion may be drawn (even though we'd both expect it to be quite deteriorated otherwise if it had been used much - it wasn't). I suspect you'll find a considerable amount of pitting in the bottom of the tank. It's also the general order of the day for weld-o-let welds to locally pit or waste faster in typical tanks & pressure vessels. As I said before, welds are the first thing to leak because they oxidize faster than the tank wall. I'm seeking a coating recommendation involving a product more readily found around the boating scene, as simply one part of only one option that is not yet ruled out. What I'm trying to tell you is, there is no coating that will extend the life of a metal sewage tank long enough to be worth the effort and expense. Removing a tank and putting it back, and also often running new piping to replace hose that has become permeated with odor is 90% of the job. Since anything you do to the existing tank now will only mean doing it again in a year or two at most, why do it twice? The Owner & I have a combined 80 years of responsible ship repair background, Peggy. That may be the problem. But I ain't no spring chicken any more either! :) The poor quality/durability of the cheap thin-walled plastic tanks sold by retailers and those used by many production builders to keep costs down have convinced many an "old salt" that metal is superior to any plastic tank...and that salvaging what was a good quality metal waste tank is preferable to replacing it with plastic. It's true that a rush delivery of a new tank of approximate & workable dimensions may be possible and that is already concurrently pursued; we may be old but we ain't dead yet. But I'm not looking for a coating option for plastic. 8-^) Well, yet. :-) You wouldn't need one. The purpose of a coating is to protect METAL from the corrosive properties of urine....plastic doesn't corrode. In any case I disagree that the old tank, even if found to be beyond interim repair, should be thrown into a dumpster right after removal. As related, it has been carefully fabricated for best & fullest fit. It will be measured & drawn for eventually fabbing a 316L tank at convenience as the Owner's preferred future installation. Someone did an outstanding job of fabbing a small tank from the wrong material; we don't throw away the good part of another's effort with the bad of their ignorance. Instead, we come up with the best interim fix we can, and then do the job *really* right. Then you do not want to use ANY metal..you'll only be repeating the previous owner's mistake. An uncoated SS tank--even thickwalled 316--has about the same average lifespan as aluminum...coating the inside of the tank only extends the life of any metal sewage tank by a few years at most. Thickwalled (min 3/8", increasing with tank size to support the weight of the contents) PE is the only recommended materal for sewage holding...rotomolded preferred...welded acceptable, keeping in mind that the integrity of a welded plastic tank depends entirely on quality of the welds. Btw...you haven't mentioned the size/type of the boat or its intended use. Most of the people who pop in only a few days before the Memorial Day or July 4th to ask how to deal with an immediate pressing problem are only looking for a short-term solution that will allow them to use the boat for the holiday. A paucity of any information to the contrary is not conducive to eliciting advice applicable to an individual's particular needs and circumstances, should such an assumption be erroneous. But I do have a sense of humor on USENET. :-) So do I. :) -- Peggie ---------- Peggie Hall Specializing in marine sanitation since 1987 Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and Other Sources of Aggravation and Odor" http://www.seaworthy.com/store/custo...0&cat=6&page=1 |
(Nice post snipped)
chuckleYou are very right in rather graciously implying with an admirable level of restraint, that a lifetime of acquired prejudice in one sector of marine life may or may not be detrimental when applied to another. It happens that we lucked out for the time being with this one by acting like commerical guys, by the grace of God, though we got damned dirty & tired doing so. ;-) Seems we're not 32 anymore. By similar Providence the associated hoses, diverter, macerator & etc. are in good serviceable cond. Sort of "a stopped clock is right twice a day" evolution. ;-) A foundational problem is this instance is that of a '70's boat never envisioned to need MSD, backfitted with a tank that entirely fills the only reasonably avail space without extensive mod, which is still only 1/2 the capacity of present-day practice, i.e. 45 USG/37' LOA motorsailer. I'm sure you've seen this movie 1,000 times, perhaps minus the same humorous cast of characters. Off-the shelf poly options reduce this to 30 USG on a good day. Were she mine, I'd consider a more extensive mod to fit more tankage of less unusual dimensions. Good news is she has a free berth alongside a commercial cargo terminal that has great heads inside. :-) Yes, austenitic SS has pitted in MSD use since we first though it'd work well in '76. (You should've seen the other & bigger boo-boos we made with early commerical MSD's.) We can get it fabbed for free, though, & flush & repassivate it view she will only be afloat 3 mos/yr for the next decade. Another issue/question arose during this minor Chinese firedrill: urethane foam. Tank had been foamed in-place for support. Naturally this made it a b*tch to break free & remove, given nearly no working clearance (with an unscheduled main halyard "stress test" in the bargaing). But I am unclear as to the use of unprotected/un-enclosed urethane foam aboard a yatch. You can't even do this ashore in a house, though there is so much other dangerous stuff to burn in a yacht that maybe it is moot. It there a r/b guideline or other generally accepted practice relating to its use aboard a yatch, which you may be aware of? BTW carpenter ants looouuuuvv urethane foam, too, as a preferred multi-unit condo, and they will find it even if it is under concrete on all sides or 25' off the ground inside a structure. BstRgds, - f. |
Seems we're not 32 anymore.
I'm continually astonished to rediscover that almost daily. A foundational problem is this instance is that of a '70's boat never envisioned to need MSD, backfitted with a tank that entirely fills the only reasonably avail space without extensive mod, which is still only 1/2 the capacity of present-day practice, i.e. 45 USG/37' LOA motorsailer. A 45 gal tank should be more than adequate for a 37' boat. In fact, it's about 50% larger than what most OEMs are installing today on boats that size. People have highly unrealistic ideas when it comes to waste holding capacity...they expect a tank to hold enough waste from a family of 4 to be able remain continuously aboard for 2-4 weeks between pumpouts...not realizing that the average volume including flush water for a family of 4 is 10 gal/DAY. Even just a cruising or live-aboard couple would need tankage big enough to turn their vessel into a floating honey barge to stay aboard continuously more than about a week. Yes, austenitic SS has pitted in MSD use since we first though it'd work well in '76. (You should've seen the other & bigger boo-boos we made with early commerical MSD's.) I have seen them...recirculating systems is only one example. We can get it fabbed for free, though, & flush & repassivate it view she will only be afloat 3 mos/yr for the next decade. Used only 3 mos/year, or used year-round...10 years is still the average lifespan of any metal waste tank. Flushing and repassivating doesn't extend it much if any...metal WATER tanks rarely survive more than 20 years before springing a leak somewhere. Good news is she has a free berth alongside a commercial cargo terminal that has great heads inside. :-) What is the make/model age of the heads on the boat? If still original--or even more than a few years old--they may or may not be worth servicing...if, in fact, any parts or service kits are still available. How many heads? Another issue/question arose during this minor Chinese firedrill: urethane foam. Don't do it...foaming in tanks is neither recommended nor necessary. For one thing, federal law requires that there be some means of determining when a waste tank is at least 3/4 full (this is supposed to prevent accidental overflows out the tank vent). If the level in the tank cannot be determined by visual inspection--which foaming it in would make impossible, a gauge is required. However, foamed in or not, if the location of the tank makes it so inaccessible that visual inspection becomes so impractical as to be impossible, you'll still have to install a gauge. Tanks rarely bounce, even in heavy seas...but they can slide if not secured. In most cases, all that's needed is a non-skid mat under it...Walmart, K-Mart etc sell some rubber kitchen shelf liner by the roll that's perfect for this application (and in the galley...NOTHING moves on it...I've seen an otherwise unsecured microwave stay put on a boat heeled 20 degrees) and straps (lawn chair webbing works well). If necessary or desired, you can also brace the corners with wood strips epoxied to the hull. So secured, the tank will not move and remains accessible for service and visual inspection. Were she mine, I'd consider a more extensive mod to fit more tankage of less unusual dimensions. Were she mine (unless she's on the Great Lakes or other inland "no discharge" waters--in which case, you can't legally use the macerator), I'd put a Type I MSD on it--specifically a Lectra/San--backed up by a small tank for use only if/when The discharge of treated waste is legal in at least 90% of US coastal waters, and is a far more ecologically sound solution to onboard waste management than a holding tank. Why store waste aboard if each flush can legally go overboard without harm to the environment? -- Peggie ---------- Peggie Hall Specializing in marine sanitation since 1987 Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and Other Sources of Aggravation and Odor" http://www.seaworthy.com/store/custo...0&cat=6&page=1 |
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Peggie Hall wrote:
Seems we're not 32 anymore. I'm continually astonished to rediscover that almost daily. I suppose as long as we don't *look like* we've been run hard & put away wet, we can keep this daily revelation in confidence. A 45 gal tank should be more than adequate for a 37' boat. In fact, it's about 50% larger than what most OEMs are installing today on boats that size. New owners tend to read "authoritative articles." Yes, austenitic SS has pitted in MSD use since we first though it'd work well in '76. (You should've seen the other & bigger boo-boos we made with early commerical MSD's.) I have seen them...recirculating systems is only one example. But I do sort of miss all those suited-up group engineroom promo sessions watching the rep drink the effluent & offer it around for sales effect - after him already having overdone it at the Downtown Athletic Club bar in studious preparation. :-) Even saw Ray Ryan take a sip once (same job as Bob Somerville now hasG). ...metal WATER tanks rarely survive more than 20 years before springing a leak somewhere. There are some that make it almost 20 yrs?? Never my good fortune even with 1/2" coated plate. What is the make/model age of the heads on the boat? If still original--or even more than a few years old--they may or may not be worth servicing...if, in fact, any parts or service kits are still available. How many heads? Naturally, 1st thought. 'Tis a '78 Fischer 37 w/1 original, not a PAR, possibly Graco, returning to her this PM. Jovially, in the case of dealing with new Owner who is also friend, patient gradualism is the strategy of success. ;-) Don't do it...foaming in tanks is neither recommended nor necessary. It's sick for 1/2 dzn reasons, never would. I was wondering if unenclosed foam was generally proscribed (anywhere) for other reasons (a side curiousity). For one thing, federal law requires that there be some means of determining when a waste tank is at least 3/4 full (this is supposed to prevent accidental overflows out the tank vent). Isn't it nice that we've legislated common sense? If the level in the tank cannot be determined by visual inspection--which foaming it in would make impossible, a gauge is required. She's so equipped. But trusting any tank indicator of any kind is another matter, yes? :-) We grew up variously feeling, tapping & test-cocking tanks daily ('cept cofferdamed cargo - those get cofferdams sounded). Licenses of competency & lives have been lost for relying on the best indicators. Ingrained practicehee-hee. Tanks rarely bounce, even in heavy seas...but they can slide if not secured. In most cases, all that's needed is a non-skid mat under it...Walmart, K-Mart etc sell some rubber kitchen shelf liner by the roll that's perfect for this application (and in the galley...NOTHING moves on it...I've seen an otherwise unsecured microwave stay put on a boat heeled 20 degrees) and straps (lawn chair webbing works well). I'm ever astonished how the fairer sex is so much better at coming up with such things. If necessary or desired, you can also brace the corners with wood strips epoxied to the hull. So secured, the tank will not move and remains accessible for service and visual inspection. We may add the oft-overlooked provision of insuring adequate bottom support along its structural length. Were she mine (unless she's on the Great Lakes or other inland "no discharge" waters--in which case, you can't legally use the macerator), I'd put a Type I MSD on it--specifically a Lectra/San--backed up by a small tank for use only if/when The discharge of treated waste is legal in at least 90% of US coastal waters, and is a far more ecologically sound solution to onboard waste management than a holding tank. Why store waste aboard if each flush can legally go overboard without harm to the environment? Too smart, Peggy - remember that patient gradualismBG? (translation: discussion deferred until he's done getting raped by the yard on more urgent & pretasked items for refloating, & has figured out how to comfortably operate half the stuff aboard, such as all the electrical toys that previous, bored owners with too much money tend to add haphazardly to such a vessel.) Type I is very fitting as he'll likely head south & bang a right at Chesapeake every year. Give me a month with him after we refloat & deliver her. :-) BTW when we were in the thick of it I did call Ron's. They are fantastic & fast to communicate & deal with, & offered me more favors than I should print here. So thanks to you there is a valuable future relationship established. BstRgds, Frank |
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