Need some advice...

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So I had a project come in the shop today, a 1950's era water cooled taffy table in need of a rebuild.  Upside down in this pic, the thing weighs about 600#. The entire top and sides are 1/2" thick steel and has a sheet of 1/4" steel bolted to the bottom. There are four chambers to control water flow through the table with an inlet and outlet pipe in the ends. 50+ years of gunk...My goal is to replace the bottom sheet (1/4") and brace the legs. The customer wants me to cut off the flange around the top and simply weld the perimeter of the sheet. My question is what would be the best approach to welding this to avoid warping? I figured I would tack the snot out of it of course but I'd like to avoid a bunch of stops and starts. I'll also be welding some angle iron across the middle to keep the bottom from developing a sag like the previous one has. Any suggestions on how best to tackle this one?
Reply:Originally Posted by AKmudMy goal is to replace the bottom sheet (1/4") and brace the legs. The customer wants me to cut off the flange around the top and simply weld the perimeter of the sheet.
Reply:Thanks Mikel, the customer wants to get rid of the bolt on idea and have it welded tight since he has been fighting leaks. The current bottom plate was so rusted it was bowing about 3/8" across the middle which was splaying the legs. He needs the bottom plate to overlap the edge by an inch or so since there is a decorative trim that goes around the table and clamps to the flange. I will have an easy fillet joint all the way around. It could still be disassembled fairly easily in the future with some grinder time or a plasma.
Reply:Leaking problems due to the state of disrepair. If you rebuild it, back to spec, it should give another few decades of leak free use.
Reply:I can appreciate the "rebuild it to spec" idea, but this customer wants it welded (not my decision...). My question is what would be the best approach to keep this sheet of 1/4" nice and flat with no distortion?
Reply:Sorry for the dumb ??  But what's a taffy table?
Reply:Originally Posted by CCFD170Sorry for the dumb ??  But what's a taffy table?
Reply:Man, I figured with all the experience on this board, someone would have a great plan of attack for this project...
Reply:I'd clean it up first to make sure the top isn't about to spring a leak. Then I'd carefully weld the legs to the bottom sheet.  After that I'd dry fit and drill the holes.  Finally, I'd silicone the **** out of it and bolt it together.My name's not Jim....
Reply:Originally Posted by BoostinjdmI'd clean it up first to make sure the top isn't about to spring a leak. Then I'd carefully weld the legs to the bottom sheet.  After that I'd dry fit and drill the holes.  Finally, I'd silicone the **** out of it and bolt it together.
Reply:I would bolt it up as well. Cleaned right and with the new much better silicons now days it should never leak again for at least another 50 years.
Reply:Tell the customer that you colleges and you have decide that unless they want a curved top table it can't be welded.  SO THERE  That should make their day   Mac
Reply:......interesting, never thought this would be impossible.
Reply:I doubt it's impossible, just that you will get just one shot at this most likely. If you want to limit warpage, 1st thing is to limit heat input. Unfortunately that also means you will have issues with good fusion. If all you need to do is get a good seal and strength isn't a big deal, then that changes some things. Jumping around will help limit heat and warpage, but when dealing with something you need to seal, all the starts and stops may cause you issues. Tig is often preferred for seal tight welds, but mig puts in less overall heat... 2nd thing would be to really think about how it's put together and what sort of joint to use. I'd want to try and make the joint as stiff as possible naturally. Welding two flat pieces in a lap joint would have a higher risk of warpage than say a T joint where the material helps to resist the pull.You might look at some of David R's posts. I know he had some issues with welding up big heat exchangers and warpage a few years back. Shame he's not around regularly any more, he might have had some insights that might have helped from his experience with those.Tough call. My 1st thought would be like everyone elses, why alter the original design if it worked before. Just stiffen up the unit and replace the bottom piece. If I had to weld it, it would be a toss up between running mig and keeping the bead as small and cool as possible or tig. I'd also be debating whether to jump around a bunch and deal with all the start/stops with the possibility of leaks, or do longer welds and risk the possibility of warpage..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:What about making the bottom plate a bit thicker say 3/8" plus the extra bracing. I think you would keep the warping down. I will say I agree building it back to original specs makes most sense. It leaked due to old seals and shear age. New sealants and careful fitment and the table would seal up terrifically.
Reply:DSW - The weld on this piece really doesn't have much structural influence, it's simply containment.  The top is all 1/2" and has three 1/2" baffles running across laterally to channel the water.  I'm going to cut off the flange with the bolt holes but the new 1/4" piece will still hang over the same amount as the flange is now so the decorative trim piece will have something to mount to.  This should give me an easy fillet weld around the perimeter with good steel exposed from the cutting.  It will also replace some of the stiffening lost after cutting off the bolt flange.  The problem is we don't have time to do a genuine restoration.  This is for a candy shop the customer is trying to open next week.  Honestly, I don't think a little warpage will be a huge issue, the 1/4" plate is on the bottom and won't be used for anything other than supporting the legs and keeping the water inside the table.  The legs have sturdy adjustable feet as well so leveling it shouldn't be an issue.  I agree, milling the mating surfaces down and bolting it with some type of a sealant involved would be the best bet, but that isn't really an option at this point.  Speaking with my metallurgy instructor last night, I think we came up with a plan....significant tacks (~1") every 10-12" then clamping the dog snot out of it with heavy channel and serious clamps.  Back skip weld in 3-4" sections then let it cool to ambient before removing the clamps.  Then I'll stitch weld some angle iron across the plate to help with any possible future sag issues.  The 1/2" top easily weighs over 300# by itself and I don't expect it to warp from the 1/4" sheet, I'm guessing the 1/4" sheet will be the one to give me issues.  I'll be tackling it tonight after work so I guess I'll update the job tonight some time.
Reply:AkmudIf the client insists that it be welded  -  get paid first.Opus
Reply:Are you certain the top isn't a cast iron piece? Based on the age and the cross ribs that would be my guess but it's hard to tell from the photos.As the others have mentioned bolting would be the correct approach. I'd simply have the flange faced if it's in poor condition, install a new seal, and start torquing bolts. Remember... this is a pressure vessel... it likely needs to keep about 50 psi I'd imagine. The flange is part of the vessel design.Even if you can keep the table flat to weld it... you'll likely be fighting an eternal problem of stress cracking along the seam. New rubber compounds are much more durable than compounds from the 50's. I've have the seal made rather than attempting to use silicone. Any boiler shop should be able to help you get the seal. A good seal should be trouble free for many years.
Reply:As with all solve jobs the answer is usually expensive.You will need a slightly undersized top plate jig, a real thick piece that clamps to the top of the finished table. this will help draw heat and keep the whole stable whilst keeping pressure just a little back from the upper rim. Tack along all sides and release pressure on the welds with a toffy hammer ( stop for a pint or quart ). weld as normal.If this doesn't work, have another drink and ring the customer in the morning.
Reply:IMHO some times it's better to save the customer from themselves. 1 you're devaluing an antique. 2 you risk warpage and other issues. 3. You've got no access to the inside of the table once it's welded. So simple repairs which could be managed with regular maintenance turn into full on rotten metal before you notices them and you've got to scrap the whole thing. Can it be welded? I'm sure it can. The question really is should it. To that I say no.There are no problems. There are only solutions. It's your duty to determine the right one.Hobart Handler 210Airco 225 Amp MSM Stinger
Reply:Originally Posted by forhireAre you certain the top isn't a cast iron piece? Based on the age and the cross ribs that would be my guess but it's hard to tell from the photos.As the others have mentioned bolting would be the correct approach. I'd simply have the flange faced if it's in poor condition, install a new seal, and start torquing bolts. Remember... this is a pressure vessel... it likely needs to keep about 50 psi I'd imagine. The flange is part of the vessel design.Even if you can keep the table flat to weld it... you'll likely be fighting an eternal problem of stress cracking along the seam. New rubber compounds are much more durable than compounds from the 50's. I've have the seal made rather than attempting to use silicone. Any boiler shop should be able to help you get the seal. A good seal should be trouble free for many years.
Reply:Originally Posted by AKmudThe cast aspect crossed my mind but I haven't had time to completely get things checked out.  I received it Monday and only had enough time to take it apart and clean out the rust. (filled a 5 gal bucket...)  Didn't touch it last night at all.  If it is cast that will pretty much make the decision for me.  It might also explain why it was bolted in the first place. There was no remnant of a gasket of any type around the flange when I took it apart.  Is it possible the mating surfaces were tight enough without one to be water tight?
Reply:Bolt it back together.  With a gasket or gasket 'goop' as the seal.As to two metal surfaces being watertight without any sort of gasket, possible but not likely.And although an 'antique' water-cooled taffy table is certainly interesting ( cool, if you will pardon the obvious pun there   ) and all that, is the client certain that current food safety health rules will allow use of a rusted/rusty ferrous table for food (candy) prep?  The best laid schemes ... Gang oft agley ...
Reply:forehire is hired.Opus
Reply:Could you run coils of tubing inside the table that water would run through like a radiator?hit the button twice...Last edited by AKmud; 05-01-2013 at 06:05 PM.Reason: double post
Reply:Originally Posted by MoonRiseBolt it back together.  With a gasket or gasket 'goop' as the seal.As to two metal surfaces being watertight without any sort of gasket, possible but not likely.And although an 'antique' water-cooled taffy table is certainly interesting ( cool, if you will pardon the obvious pun there   ) and all that, is the client certain that current food safety health rules will allow use of a rusted/rusty ferrous table for food (candy) prep?
Reply:Just build a new one from 1/2 inch stainless! Its only money. Haha
Reply:Envelope please........................ it is cast iron. I called the owner and gave him the news. Now it is time to see if there is a machine shop somewhere nearby that can knock out 100+ holes in a 300+# table top quickly. I really don't want to take the time myself...... but I bet I can't leave it alone. Time to go burn up a drill motor.
Reply:Funny how the right answer ends up being the right answer, ain't it?
Reply:Originally Posted by Fnord5Funny how the right answer ends up being the right answer, ain't it?
Reply:Here's where it sits now. I'll be picking up new hardware tomorrow and the customer is working on getting a piece of rubber gasket material. I hit the flange with a flap disk to get rid of what appeared to be some kind of gasket material (buried under the rust) and wire wheeled all the loose rust from the inside of the chambers. Last question for tonight....Is there a good rust inhibiting product out there that could handle being submerged in water for years on end? I was thinking about trying to paint the inside surfaces with something to slow the rust before we put it back together.
Reply:I'd hose down the inside with silicone spray and call it good.  Stay off the gasket flange.  Anything you paint it with has the possibillity of peeling off and pluging up the works.Those holes wouldn't be bad to drill by hand.  Just use a good pilot bit.  I'd flip it over and clamp it together, then drill about every sixth hole.  Put bolts in those holes and then go to town on the rest.I'd have half of 'em drilled in the time it takes you to load it and go to the machine shop.  They'd just end up drilling them by hand anyway to ensure alignment.  This would be an excellent use for a mag drill.  You could prolly skip the pilot hole then.My name's not Jim....
Reply:Would be a good spot for POR-15 in multiple layers. However painting something like this takes away from its cooling effect on the table some.Do they have to use strait water in the table? A water and some sort of oil mix to battle rust would be nice if it is possible to use.
Reply:Originally Posted by Boostinjdm  This would be an excellent use for a mag drill.  You could prolly skip the pilot hole then.
Reply:Originally Posted by DSWJim Colt would probably just layout all the holes on his CNC plasma and walk away...
Reply:I thought about suggesting your CNC mill, but I wasn't sure if your table was big enough... .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:Actually, the holes were already drilled in the last pic I posted, you can see the oil marks and the new 1/4" piece with holes is on the floor behind the sawhorses.  I basically didn't WANT to do it.... My other option for the evening was crashing on the couch and getting nothing done.  Obviously I couldn't sit still that long so I got after it with two drills.  Knocked out a few corner holes and bolted them then wiped out the rest of them.  It's ready for some kind of sealant at this point and after the customer comes up with a gasket it can all go back together and I'll weld the legs up.  Good times.
Reply:Originally Posted by DSWI thought about suggesting your CNC mill, but I wasn't sure if your table was big enough...
Reply:I threw a 3/16" pilot in and was done in less than an hour....
Reply:Originally Posted by AKmudIt's ready for some kind of sealant at this point and after the customer comes up with a gasket it can all go back together and I'll weld the legs up.
Reply:Originally Posted by forhireGlad your all drilled. Permatex makes some gasket material called The Right Stuff that works great. Generally comes in a can like cheese whiz but looking at their site it also comes in a chalking tube. Much better than silicone. It might be just the thing if your not going to have a rubber gasket made.http://www.permatex.com/products/our...he-right-stuff
Reply:Originally Posted by AKmudWill that stuff handle the movement from temperature changes this thing will go through?  I was speaking to my customer yesterday and he said they can change from cold water to hot water depending on the application so this table will probably go through a lot of movement due to the temp changes.
Reply:Originally Posted by AKmudWill that stuff handle the movement from temperature changes this thing will go through?  I was speaking to my customer yesterday and he said they can change from cold water to hot water depending on the application so this table will probably go through a lot of movement due to the temp changes.
Reply:Well, she is all done and ready to load up. We ended up using a sheet of rubber gasket material about 1/8" thick. Other than being a pain to line up, it went together pretty well. I got the new leg assembly welded up with the bottom sheet bolted in place. After everything was welded up and had a chance to cool I disassembled the table, flipped it over and fit the rubber sheet, drilled all the holes in the rubber then fought with the 300+# top till I got all three sets of holes lined up. Got my wife and a kiddo to help bolt it all down and torqued, then gave the leg assembly a fresh coat of gloss Rustoleum. Now she is strapped up and ready to be picked up tonight.  Thanks again for the help/advice!
Reply:Looks good. Let us know if it leaks.
Reply:Originally Posted by forhireLooks good. Let us know if it leaks.
Reply:Did you pressure test it?