|
|
I'm bidding a job for someone who needs to replace a ~22 gallon plastic fuel tank in his boat. The plastic tank has started leaking. He wants a smaller tank, made from aluminum as a drop in replacement. Below is a quick sketch.Positions for vent/pickup and filler cap are approximate. No mounting tabs are shown. The dimensions are all approximate at this point. I'm just trying to size a container with the correct volume and roughly the right shape, so I can price the material and estimate the fabrication time.I'm most interested in your comments on the baffle design. The sketch shows them as going all the way to the top of the tank, but I plan on leaving them a little below, so there's a way for air to move freely within the tank.2nd picture shows how I think I'd have the pieces formed before assembly. Anybody have any better ideas from past experience? I think there's plenty of room for TIG welding the baffles into the bottom and sides, and then welding the piece that makes up the top and ends....Thanks. Attached ImagesBenson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:You will need at least one "hole" near the tops of the baffels so that air can vent. I would cut some intermediate holes in the baffels so it will fill faster myself. Round holes and then dimple them would be my 1st thought. I might also just clip all 4 baffel corrnes at a 45 deg angle.I like the sketch, what program did you use?
Reply:I would consider adding a lip to the bottom and sides. Mayb 1/2" lip, it would save some fit up time and you'll be able to go a little faster rather than corner to corner welding.
Reply:Good pattern layout Dab! A small tank like that, use .090 5052 aluminum, and you are good to go. I agree with a few more holes for faster filling and fuel flow while underway. Sloshing slowed is good, even with several 1-1/2" holes in the baffles.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:Yeah, there's a mistake in the sketch. I was thinking of bringing the baffles up and leaving an 1" gap at the top of each one to allow air movement.Does cutting all the corners defeat the purpose of the baffles?I modeled these after some sumps I've seen that are designed to keep recirculating pumps from picking up any big debris that gets into the tank. I figured this would be good for keeping any trash that falls into the filler cap from easily being drawn into the fuel pickup.I suppose I could put a couple 2" dia holes in the baffles at different heights....The sketch is made with google sketchup. Which I initally disliked, but managed to wrap my head around after a couple hours practice. 3D modeling really takes a different point of view than 2D drawing... Originally Posted by DSWYou will need at least one "hole" near the tops of the baffels so that air can vent. I would cut some intermediate holes in the baffels so it will fill faster myself. Round holes and then dimple them would be my 1st thought. I might also just clip all 4 baffel corrnes at a 45 deg angle.I like the sketch, what program did you use?
Reply:I hadn't thought the outside corners would be a big deal...But I see where distortion could make getting tight fitup a problem. How about using some 1/2"x1/2"x1/8" aluminum angle along those outside edges? This would require clipping 3/4" from each corner of each baffle for ease of installation?Might make for a stiffer tank...? Originally Posted by 19662I would consider adding a lip to the bottom and sides. Mayb 1/2" lip, it would save some fit up time and you'll be able to go a little faster rather than corner to corner welding.
Reply:Thanks Rojo. I did a search of old posts about fuel tanks and cobbled the design and material specs together from those and what I found on summitracing for commercially manufactured fuel tanks. Originally Posted by RojodiabloGood pattern layout Dab! A small tank like that, use .090 5052 aluminum, and you are good to go. I agree with a few more holes for faster filling and fuel flow while underway. Sloshing slowed is good, even with several 1-1/2" holes in the baffles.
Reply:I would leave it as corner to corner fit up if it were mine, I don't think you'll have a hard time to fit aluminum.
Reply:Originally Posted by A_DAB_will_doYeah, there's a mistake in the sketch. I was thinking of bringing the baffles up and leaving an 1" gap at the top of each one to allow air movement.Does cutting all the corners defeat the purpose of the baffles?I suppose I could put a couple 2" dia holes in the baffles at different heights....
Reply:A quick question for you Rojo. When you've made these tanks in the past, did you weld the baffles on both sides, with fillets that run the full length of each side? Or can you get away with stitch welding them, say 1" of weld spaced 1" apart, on one side only?here's the latest version, incorporating comments so far... Originally Posted by RojodiabloGood pattern layout Dab! A small tank like that, use .090 5052 aluminum, and you are good to go. I agree with a few more holes for faster filling and fuel flow while underway. Sloshing slowed is good, even with several 1-1/2" holes in the baffles.
Reply:A Dab,Couple suggestions:When fabbing the baffles, lay the entire sheet out lengthwise. Use a holesaw to cut a couple 2" holes along the cut lines. Cut the baffles. That way you've cut 4 holes and made two straight cuts and the baffles are ready.I prefer to have my baffles extend all the way to the bottom of the tank at the sides. Just a little stronger this way. Baffles can be tacked/stitch welded. A continuous weld will cause too much deformation in the sides.You're going to need some vent holes at the top of the baffles (if the baffles go to the top of the tank) so that air pockets don't keep the individual "cells" from filling. I'd stop the baffles about 1/2" from the top if it were me.May also want to consider adding a "cleanout" port while the tank is being built. A small tank like this can be taken out and "dumped" but a port makes the process easier. The new ethanol fuels are playing he11 with marine engines and fuel systems (tanks). They draw moisture like a sponge.Last edited by SundownIII; 07-07-2009 at 12:37 PM.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:You'll want a cleanout port in each cell...
Reply:Originally Posted by A_DAB_will_doA quick question for you Rojo. When you've made these tanks in the past, did you weld the baffles on both sides, with fillets that run the full length of each side? Or can you get away with stitch welding them, say 1" of weld spaced 1" apart, on one side only?here's the latest version, incorporating comments so far...
Reply:Thanks, I'll talk with the customer about a cleanout. It'll be his call. I figured on 1/8" thick material just to make it a little easier to weld. I don't think weight is much of an issue with a tank this small.Will cut down to 2 baffles, and redesign the pass-throughs based on yours and Sundown's advice.Thanks for the warning about distortion. My welding table is 3' x 3', and I'd figured on clamping one side down flat while welding in the baffles. Once the baffles are done, I figure the tank aught to be pretty rigid, so the top and side section won't pull too much out of square.Will let you know what the customer says and, if he agrees to the quote, I'll post photos of the project as it goes along.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:built a couple of tanks for boat and cars in Alu.in this thread http://weldingweb.com/vbb/showthread.php?t=26911 i have some pics of the most recent tank i did with baffel design.
Reply:Larry,Thanks for the link. I'm just wondering, with so many holes cut in the baffles of the tank you made, do they really help prevent fuel starvation? Or do they just become structural members in the tank?My impression is that the baffles are supposed to keep fuel trapped in the vicinity of the pick-up, without starving the pickup of fuel volume. Any structural support they provide is incidental or secondary to their main purpose...Somebody tell me if I'm wrong in my understanding...One other thought that occurred to me. I don't have a break to make the bends I'm planning on the tank components. My metal supply house does, and they work for relatively low cost when it comes to cuts and bends. Is there any difference or problem with 90° bends in either 3/32" or 1/8" thick 5052 aluminum sheet? Should I have any worries about splits or cracks in those bends? My gut says no...Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:In smaller tanks you only need to retard the movement of fuel a little.it does also become strucual. ( help with pressure testing )
Reply:The .090/ 3/32" aluminum bends very well. There is a backset on a pinch break; the further back you set it, the wider the bend will be in radius. For thin sheet, you go flush tot he crease. For aluminum like this, you will backset the pinch 1/16" to 1/8". It gives you a gradual bend that does not crack.Baffles do it all, prevent fuel slosh, prevent foaming, keep fuel near the pickup, and strengthen the tank.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:My 2 cents worth (hey I'm cheap :-) )As was said crop the corners of the baffles 1 1/2" x 1 1/2".Bend a 1" or so flange around four sides of the baffles, it'll allow he baffles a minor bit of flexability and will prevent the welds from pulling out of the shell from the fuel hitting it. Make sure you weld on the edge of the bent baffles not on the actual bend.The shell is going to warp from welding the bafffles in so be aware the edge of the shell will not be straight and might pose a problem during assembly.. Me, I'd use a wire feed to weld in the baffles (faster welding =less warpage)and instead of making the shell in two pieces I'd make it in four, two long pieces bend to an angle and two ends. That way you can weld the baffles in after assembling the two long sections into a square tube.The ends, I'd bend a flange on them the same as the baffles wihout the cropped corners and leave them out 1/2" or so, that way you have reinforcement on the ends and more materal to work with.I've made tanks before and it works for me, I'm always open to suggestions tho.....Mike
Reply:Free surface liquids is the term used to describe a space partially filled with liquids that can slosh around.In a boat or ship a partially flooded compartment is much more dangerous than a completely flooded one.I forget the exact weight, but lets say fuel is 7 lbs to the gal for example. if the tank is 1/2 full and holds 16 gal, then the weight of the fuel is 48lbs. 48lbs slamming from one side of a tank to the other can act like a hammer in rough conditions causing failure. By using baffles you accomplish 2 things, one you reduce the "volume" that can move, and 2nd you reduce the distance that weight can move. I'm sure you remember sloshing water from end to end in a tub as a kid. Remember how it pushed you back and forth once you got it going?Failure is kind of extreme in the case of something this small, but it's part of the reason for baffles, besides keeping fuel near the pickup, and adding strength.
Reply:Yet another thing that is bad about sloshing is the noise that it makes. This is less of an issue in a fishing boat, but when talking about sailboats that people live aboard, it can be a big problem... especially when the tank is underneath a settee that someone uses to sleep on.
Reply:Originally Posted by A_DAB_will_doHow about using some 1/2"x1/2"x1/8" aluminum angle along those outside edges? This would require clipping 3/4" from each corner of each baffle for ease of installation?Might make for a stiffer tank...?
Reply:In the attaches pdf you will see how I make most all my baffles Attached Imagesbafl.pdf (44.4 KB, 556 views)
Reply:Good suggestions all around. Thanks for all the advice, and design mods.To answer some of the latest points brought up. - I'll be TIG welding the whole tank. Not going to buy a spool gun for this project, but might in the future if more aluminum work comes my way...- I'll think about bending tabs onto the sides of the baffles, but I'll have to take a look and make certain the little pan brake I have is up to the challenge. Might just jury-rig a bender with my work table and some angle iron...- Since I'm TIG welding this, I'm trying to eliminate weld joints where I can. That's why I opted for the 2 piece shell. Time = money, after all.- DSW, thanks for the reminder about the dynamic forces involved. - Fat Bastard, thanks for posting the drawing of your baffle design. I'll get some more revised drawings up, once I hear from my customer.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:http://weldingweb.com/attachment.php...1&d=12470756781-stitch welding baffles on tank inside, can create cracking in use from the fuel slamming, especially in aluminum. Yes, side wall distortion is a problem, it's eased by welding the flanges,first lots of tacks, then sequential weld paths, with water cooling to take the heat out promptly,air blow-off and weld the next 2-3", etc.2-Anymore, I weld the baffle flanges-fully on the flange side. then fully weld the head flangesinside and out. I just prefer to make stout tanks, especially if they're subjected to lots of movement,in the end use application.3-the top flanges of the heads and baffles are set to contact the underside of the top 'wrap' piece--formed like a U, to cover the top and overlap the sides, in this example. The top 'wrap' isthen plug welded to the baffle flanges below. Attached ImagesBlackbirdDave,Thanks for the comments and the photo. I like the "pan" that makes up one end of the tank shown in the photo you posted. Looks stiff and strong, and like it would take less welding than using pieces of angle to reinforce the corners and make the welds into lap joints; rather than open root outside corners.Are all the holes drilled in the sides, near the top, for plug welds? Or just for temporary screws to hole the top in place while you weld the edge seams? If yes, isn't it a nuisance to weld all those holes shut again?Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Originally Posted by A_DAB_will_doDave,Thanks for the comments and the photo. I like the "pan" that makes up one end of the tank shown in the photo you posted. Looks stiff and strong, and like it would take less welding than using pieces of angle to reinforce the corners and make the welds into lap joints; rather than open root outside corners.Are all the holes drilled in the sides, near the top, for plug welds? Or just for temporary screws to hole the top in place while you weld the edge seams? If yes, isn't it a nuisance to weld all those holes shut again?
Reply:Thanks for the followup explanation Dave. I hear what you've said about locating the tank fittings in the corners. I'll relocate them closer to the corners in the final plan, subject to them fitting in the cavity in the rear of the boat hull. I'll need to hear a commitment from the customer before I spend a lot of time incorporating the modifications suggested here. I've got a local shop that supplies steel and aluminum that I like working with. They do some fabrication work as well, but I haven't asked them to do much of this in the past. I'm not sure what their level of expertise is, so I'll make sure I'm clear on what I want bent, and how with this project. If I can do it myself in my own shop I would. The small stuff I can, like tabs on the baffles, and the top section. But the 3' long bends to form the sides and bottom will have to be done by somebody with larger equipment...Once I get an OK to proceed and order material, I'll post the final, customer approved design. I might ask for some more photos or suggestions when I get to that point.Thanks again. Time for dinner and sketching some ideas for another bid I was asked for today....Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:This is one interesting post. May I ask, at what point does it become necessary to install baffles? I have a small 6 gallon tank I have been thinking of building and then a 24 gallon. Are there some guidelines that dictate at what point baffles and other criteria are needed. Thanks, Great work gents.
Reply:Originally Posted by geezerThis is one interesting post. May I ask, at what point does it become necessary to install baffles? I have a small 6 gallon tank I have been thinking of building and then a 24 gallon. Are there some guidelines that dictate at what point baffles and other criteria are needed. Thanks, Great work gents.
Reply:Cracking thru and leaking from a flimsy, poorly designed/welded mount system is common
Reply:My solution for the cracking mount has been to use a reinforcing plate to the tank wall, usually it wraps a corner, and is welded all around. The mount is then centered on the reinforcing plate and welded all around. Then when ever I can I mount the tank via spring bolts. Many of the large truck mounted tanks (water trucks, $hit suckers) the tank will be hard mounted at the cab end and spring mounted at the tail end.
Reply:Originally Posted by dave powelsonhttp://weldingweb.com/attachment.php...1&d=12470897824-If you wish other pics of details, I can post those later.
Reply:Well,Met with my customer last night and hammered out the final details. Got verbal approval to proceed. Ordered the material for the tank today, and finalized the drawings. Sent the drawings to the customer along with a written quote.Here's the finished version: Attached ImagesBenson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Looks good. I can't wait to see the build picts.
Reply:Head space, fuel picks, sending unit timing?A DAB--I don't know how much tank design you've been involved in, soI'll mention several more items:1-Head space and volumes-Allow a minimum of of 10% of the liquid volume for heat expansion with gas as fuel. Fuel oilor diesel is 6%.-head space is created by extending the top fill neck tube (and sometimes the top vent tube--depending on the venting arrangement), down into the tank top; an amount calculated to create an air pocket that helps prevent overfilling of the tank, also a place for heat expanded fuel to go to.(Yes, some of the expanded fuel volume can go back up the filler tube and the top vent.) In your current design, the vent tube could be extended. If the fill opening of the fuelfiller hose assembly is located quite a bit higher than the tank, this will compress the air pocket, implying that more headspace should be allowed. Depending on headspace volume calc's.the filler tube neck end inside the tank could be cut at an angle, so that the tube end runsparallel to the bottom of the tank. Head space creates a volume inside the tank, that is subtracted from the tank's theoreticalvolume.2-Fuel pickups:-if the end is simply a cut end of tube, weld a washer on the bottom of the tube. This helpsprevent tank wall puncture. -the pickup tube need to be spaced away from the bottom, to prevent contact and allowfor fuel pickup. (On some pickups, I've ground slots in the tube sides, as well.)-this open space of the fuel pickup creates a volume of fuel in the tank bottom, that willbe 'unusable fuel'.3-Usuable fuel is theoretical volume - (headspace + fuel pickup loss).Normally, these calc's. are one of the first things done, to estimate tank size & form--comparingthis to customer requirements.Putting this in writing to the customer is suggested.The actual fuel usable may be less dependent on the pitch of the boat, tank location, etc.4-Sending units-always test for function, electrically before beginning installation, swinging the armthru full swing with an ohmmeter-insure that the timing of the fuel sending unit, allows for free swinging of the arm andno possible contact to the baffles, sides, bottom, etc. of the tank.5-Adding a grounding tab--for tank and sending unit grounding is a real good idea. (All of the above are pesky little details that are mostly ignored.)Blackbird
Reply:Not much previous tank design experience dave, so I appreciate the insights. Thanks for the advice.Tank volume(theoretical) is just a bit more than 3200 in3, or about 14 US gallons. I hadn't given much thought to head space, but it'd be easy to extend the filler neck down into the tank to create some head space. If 10% is the rule of thumb, it shouldn't be too much of a problem to calculate the extension into the tank that's needed.The customer is replacing a 22 gallon plastic tank that's leaking due to old age. The boat is mid 80's vintage, and the tank is a custom OEM piece that's no longer available. He wants a smaller tank, and 13-15 gallons is right about where he want's to be. I'll discuss the headspace issue with him before starting fabrication.Fuel capacity isn't too much of an issue in this bass boat. According to the owner, he fills the current fuel tank every 2 - 3 days during constant use while fishing. Half the volume in the new tank will still let him run all day long on a single fillup.The fuel filler neck isn't much higher than the top of the tank, so there won't be much head pressure if the tank is filled to the top. The neck is less than 24" long, 1.5" diameter flex tube.The fuel pickup is going to have a mesh filter cap installed on it, and the neck is some kind of flex tubing. The customer is handling all of this, and so the burden is on his shoulders. With the metal mesh filter, the filler should rest on the bottom of the tank, so there won't be much dead space. The boat engine is an older Evinrude 115 outboard, and according to the owner it won't tolerate any air in the fuel line. If nothing else, I'll make certain he cuts the end of the pickup tube at a 45° angle, so it doesn't self-seal against the bottom of the tank.I have the sending unit in hand, and will test it before beginning that phase of the project. I took the middle baffle out of the design specificly to ensure that there was room for the float on the sending unit to swing freely inside the tank. The reinforcing pad for the sending unit is extra large, and I'll find a convienent place to mount a ground connection. Originally Posted by dave powelsonHead space, fuel picks, sending unit timing?A DAB--I don't know how much tank design you've been involved in, soI'll mention several more items:1-Head space and volumes-Allow a minimum of of 10% of the liquid volume for heat expansion with gas as fuel. Fuel oilor diesel is 6%.-head space is created by extending the top fill neck tube (and sometimes the top vent tube--depending on the venting arrangement), down into the tank top; an amount calculated to create an air pocket that helps prevent overfilling of the tank, also a place for heat expanded fuel to go to.(Yes, some of the expanded fuel volume can go back up the filler tube and the top vent.) In your current design, the vent tube could be extended. If the fill opening of the fuelfiller hose assembly is located quite a bit higher than the tank, this will compress the air pocket, implying that more headspace should be allowed. Depending on headspace volume calc's.the filler tube neck end inside the tank could be cut at an angle, so that the tube end runsparallel to the bottom of the tank. Head space creates a volume inside the tank, that is subtracted from the tank's theoreticalvolume.2-Fuel pickups:-if the end is simply a cut end of tube, weld a washer on the bottom of the tube. This helpsprevent tank wall puncture. -the pickup tube need to be spaced away from the bottom, to prevent contact and allowfor fuel pickup. (On some pickups, I've ground slots in the tube sides, as well.)-this open space of the fuel pickup creates a volume of fuel in the tank bottom, that willbe 'unusable fuel'.3-Usuable fuel is theoretical volume - (headspace + fuel pickup loss).Normally, these calc's. are one of the first things done, to estimate tank size & form--comparingthis to customer requirements.Putting this in writing to the customer is suggested.The actual fuel usable may be less dependent on the pitch of the boat, tank location, etc.4-Sending units-always test for function, electrically before beginning installation, swinging the armthru full swing with an ohmmeter-insure that the timing of the fuel sending unit, allows for free swinging of the arm andno possible contact to the baffles, sides, bottom, etc. of the tank.5-Adding a grounding tab--for tank and sending unit grounding is a real good idea. (All of the above are pesky little details that are mostly ignored.)
Reply:[QUOTE=A_DAB_will_do;299352]Not much previous tank design experience dave, so I appreciate the insights. Thanks for the advice.The fuel filler neck isn't much higher than the top of the tank, so there won't be much head pressure if the tank is filled to the top. The neck is less than 24" long, 1.5" diameter flex tube.1-Fuel fill and vent hoses:-use fuel rated hoses-only. Using heater or radiator hoses is anything but safe, cheaper yes,safe-no. (I once had a motor home in for tank inspection/repair. Did my thing-told customerthe hard, cracked radiator hose used as a fill hose needed replacement. Of course he refused.Fills it up, comes back to shop, pissing gas all over the place--de-fuel the tank, replace with green stripe, new clamps, and hand him the second bill.)The 'Green $tripe' for fill hose (for example) is coated inside to resist fuel degradation. It doesn't bend easy--so the angle of the dangle, fuel tank neck to filler cap neck needs to be looked at.-Coating the outside of the metal connecting tubing, inside of the hose connection area with silicone based grease, helps get good hose clamp sealing--that stays tight.....and.......and............and makes removal of the hoses so much easier.Blackbird
Reply:1-Tank positioningOn fresh or saltwater boat tanks, the bottom should be raised up for about 3/8" or more air gapunder the tank--to prevent constant water contact with the aluminum. The tank bay should be freelydraining down to the bilge. Water should never be allowed in constant contact with the tank.Letting the tank rest on outdoor carpeting/foam rubber, etc. is guarantee for corrosion.2-Tank finishingOne low cost option after fab- is to wash the tank exterior, wipe down with lacquer thinner, thenswirl polish the tank exterior, with 3M Fibratex abrasive pads (or equivalent) in angle grinder.Besides the appearance aspect, this seems to really cut down on water corrosion. I've had weather exposed alum. done this way, in service for over 10 years and it still looks good. I use the fibratex to prep alum. surface for 'bite', also if it's to be powdercoated. Powdercoating an aluminum tank (which I've never had done), requires extra special careon baking temp's. by the coater--who should already have experience in coating thin aluminumparts without screwing them up; and a type of steel fixture to suspend the tank from, to avoid distortion of the tank and mounting system. A 375-400 degree bake is enough to begin softening the aluminum, plus possibly putting some unwanted 'wows' in the tank shell. If the coater doesn't have a really good handle on temp monitoring and controls, they can ruin the alum. part. (I fabbed 2, 2' x 12' ,long, thin, flimsy, architectural signs, which received 3 different, masked p-coat colors...and that required prior discussion with the coater on hanger points and a special baking rack hanger.)http://weldingweb.com/attachment.php...1&d=1247711791 Attached ImagesBlackbird
Reply:Don't make this too complicated, I've never seen a boat fuel tank formed in a brake. They always start as flat sections that get welded together. Do it right, make it from 5000 series marine aluminum and use the baffles as stiffeners to support the walls of the tank. That means you'll weld everything on except one side parallel to the baffles so you can climb inside the tank and weld the baffles in to all sides before you close it up. For a tank that size, 1/8th inch would be adequate, 3/16ths would be excellent. No coatings are required but proper installation techniques should be followed. 5000 series aluminum will protect itself but it does need to be exposed to air to prevent crevice corrosion so don't seal it in. Strap it down, throw a litlte 5200 on the areas where it does rest against other materials (this will prevent moisture from getting to the aluminum in the areas not exposed to air). This is a very tolerant material, it doesn't matter what you do or don't, you probably wont have an issue within an unreasonable time frame.Last edited by 76GMC1500; 07-16-2009 at 02:43 AM.
Reply:Finished the tank and finally am getting around to posting the photos I snapped. Attached ImagesBenson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Thanks for all the advice. Customer is very happy and that's the most important thing. Attached ImagesBenson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Having the main portion of the shell formed into a U by my metal supplier was a blessing and a curse.He cuts pretty straight, but the alignment on his brake must be a little off. It was nice not having to weld the bottom seams of the long sides of the tank. But the fitup on the end plates and top wasn't perfect, so the weld appearance was a little rougher than I like. Welded those seams vertical up and didn't have too much trouble filling the gap and rounding over the corners. They don't look perfect, but they're sound welds. Originally Posted by 76GMC1500Don't make this too complicated, I've never seen a boat fuel tank formed in a brake. They always start as flat sections that get welded together. Do it right, make it from 5000 series marine aluminum and use the baffles as stiffeners to support the walls of the tank. That means you'll weld everything on except one side parallel to the baffles so you can climb inside the tank and weld the baffles in to all sides before you close it up. For a tank that size, 1/8th inch would be adequate, 3/16ths would be excellent. No coatings are required but proper installation techniques should be followed. 5000 series aluminum will protect itself but it does need to be exposed to air to prevent crevice corrosion so don't seal it in. Strap it down, throw a litlte 5200 on the areas where it does rest against other materials (this will prevent moisture from getting to the aluminum in the areas not exposed to air). This is a very tolerant material, it doesn't matter what you do or don't, you probably wont have an issue within an unreasonable time frame.
Reply:Looks really good, how long did it take to build?Miller Dynasty 300dxSpeedglas 9002XMiller Spectrum 375 XtremeLincoln PowerMig 255xtLincoln PowerMig 140cMilwuakee Portaband
Reply:Tough to say exactly. The customer wasn't in a hurry, he was doing other maintenance to the boat engine. I worked a few hours at a time on the tank, inbetween some other jobs. I got the tank to him at the point he was finishing up the engine teardown.There's probably 15 hours in it. But that includes running around to buy materials, some specific hole saws, filler metal, etc. Made a couple repeat trips as I needed some pieces bent to specific dimensions and messed around with getting the filler neck tubing in the right dimensions.Actual fabricating and welding time could have been ~10 hours, with me learning as I went. I spent some time back tracking at one point, to fix a minor mistake. "Measure twice, cut once." I also spent some time thinking about the right order to assemble the filler neck pieces, while still being able to weld them all easily together.There's about 2/3 lbs of filler metal in the welds, and about 300 PSI of Argon. Originally Posted by sidthssLooks really good, how long did it take to build?
Reply:Looks real good! Nice work and a clean shop!
Reply:Looks good, nice job. Thanks for letting us know how it turned out in the end..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Originally Posted by A_DAB_will_doI'm bidding a job for someone who needs to replace a ~22 gallon plastic fuel tank in his boat. The plastic tank has started leaking. He wants a smaller tank, made from aluminum as a drop in replacement. Below is a quick sketch.Positions for vent/pickup and filler cap are approximate. No mounting tabs are shown. The dimensions are all approximate at this point. I'm just trying to size a container with the correct volume and roughly the right shape, so I can price the material and estimate the fabrication time.I'm most interested in your comments on the baffle design. The sketch shows them as going all the way to the top of the tank, but I plan on leaving them a little below, so there's a way for air to move freely within the tank.2nd picture shows how I think I'd have the pieces formed before assembly. Anybody have any better ideas from past experience? I think there's plenty of room for TIG welding the baffles into the bottom and sides, and then welding the piece that makes up the top and ends....Thanks.
Reply:Originally Posted by 76GMC1500Don't make this too complicated, I've never seen a boat fuel tank formed in a brake. They always start as flat sections that get welded together. Do it right, make it from 5000 series marine aluminum and use the baffles as stiffeners to support the walls of the tank. That means you'll weld everything on except one side parallel to the baffles so you can climb inside the tank and weld the baffles in to all sides before you close it up. For a tank that size, 1/8th inch would be adequate, 3/16ths would be excellent. No coatings are required but proper installation techniques should be followed. 5000 series aluminum will protect itself but it does need to be exposed to air to prevent crevice corrosion so don't seal it in. Strap it down, throw a litlte 5200 on the areas where it does rest against other materials (this will prevent moisture from getting to the aluminum in the areas not exposed to air). This is a very tolerant material, it doesn't matter what you do or don't, you probably wont have an issue within an unreasonable time frame.
Reply:Originally Posted by William McCormick JrThe baffles ...........The tank wall will give, and you do not want the baffles to hold it that rigidly. It could pull the welds through. Never mind it looks great. Just went back and read further on. Sincerely, William McCormick |
|
发表于 2021-8-31 23:55:15