This one's short and thick, like Panhead John's lady friends. 
30" diameter tank, 48" long, but only a little over 26" between the seams. 125-gallons. This tank is essentially exactly one half of the previous 250s I've built out as the Mk48 and the Mk48.2 that I built for the guys at Hogmollie BBQ. This will probably go on another yard cart, but not sure what I'll do about wheels and such yet. I have a couple of set of golf cart wheels I could use, but once I got them on, I thought they looked a little dinky on previous builds. I thought about some big casters, but that makes it really tough to move in grass, and getting it in and out of the shop every day (or multiple times a day, often) would be a bear. So... who knows. I'll have to see where the build takes me. This is in the development stages for now.
Anyways, this little(ish) tank had a lot of valves and gauges and stuff, all lined up on one side, which makes for a challenge when it comes to cutting them out and patching the tank. If there are 2 or 3 gauges and they've got some space between them, it's not too hard to cut them out and weld in square or round patches. But these are really too close together for that, which means... things are a bit more complicated.
Here's the tank once I used the plasma to cut a hole in the head after filling with 30 or 40 gallons of water and dish soap.
Cutting out a large section like that presents its own challenges. Namely, structural integrity, but this isn't a weight-bearing structure or anything like that, nor will it be a pressure vessel ever again. BUT, when you cut out large pieces, it relieves some of the stresses in the metal, and adds new ones when you weld in a new chunk. Heat affects things, as well. The concern is what's going to happen to it when you cut a door into it? Well, the door is going to be on the opposite side as these gauges, but the stresses and heat can still affect it from the other side anyways. And you have to think about the weld seams from when the tank was originally rolled from a single sheet of steel and welded together. The longitudinal weld seam on this tank is along the bottom, as it sits in this pic. You really want your door to be far away from the weld seams, as that is where the most heat and stress have been applied, but I'm also about to create MORE weld seams in it, too. Oh well, not much you can do about it but deal with it, right? Right! I can work on reshaping a door (or the tank) if it pops or relaxes once it is cut out. Just gotta do what you gotta do.
So... first I took my Dewalt slicer to it, but in trying to get as close to the valves as I could, I was worried about lateral stress on the cutting wheels and a wheel shattering and putting my eye out or something, like in the movie A Christmas Story. Definitely didn't want that, so I ended up moving the tank into the shop and cut it free with my new plasma cutter (Primeweld CUT60). Here it is after cutting it free.
Then to decide how to make the patch. Hmmmm...
I could have just cut some steel plate and welded it in place, but that would be flat, and wouldn't match the contour of the rounded 30" diameter tank. For small patches, sometimes this is ok, but if you want it to look decent afterwards, it's much better if you contour your patch. But how to do that?
I decided to use my band roller, which is a handy tool, but I can only roll 3" strips at a time. First rule of getting good cuts with plasma is meticulous layout of your cuts, and then using a guide to run your torch along. This took some effort to get set up, but it is worth it to get good material to work with. Have to mark where you want to cut, and then calculate the offset from your guide to the opening on your plasma cutter and factor in the kerf thickness as well. Then how much you're going to take off with the grinder flattening it out and cleaning it up afterwards, as no plasma cut is perfect unless you're using a CNC plasma table - or at least mine aren't! Here is one of my cuts laid out and ready to go.
Luckily my 2 pieces ended up exactly 3" wide, then I used my roller to bend them little by little and matched them to the curvature of the tank itself.
Now marked to cut into sections 5 1/8" long, which is the 'height' of my opening in the tank.
Cut section beveled to allow for better welding.
Coupons also beveled and aligned to make up my patch:
Tacked together:
Then tacked together on front, cut loose and heavily tacked on backside to prevent warping of my patch when I fully weld it all together.
I took it all outside and ground down all the tacks to be smooth on the inside of the tank. I'll need to trim it down some, as it's about an inch too long (I wanted to give myself some 'wiggle room' for error), then clean up the bevels, and weld it all in place, probably tomorrow.
So this is the method I used for patching this tank. Hopefully it'll all come out well once I get it welded in and grind everything down and it'll look pretty close to the original tank contour.
We shall see...
More to come tomorrow or later in the week.
30" diameter tank, 48" long, but only a little over 26" between the seams. 125-gallons. This tank is essentially exactly one half of the previous 250s I've built out as the Mk48 and the Mk48.2 that I built for the guys at Hogmollie BBQ. This will probably go on another yard cart, but not sure what I'll do about wheels and such yet. I have a couple of set of golf cart wheels I could use, but once I got them on, I thought they looked a little dinky on previous builds. I thought about some big casters, but that makes it really tough to move in grass, and getting it in and out of the shop every day (or multiple times a day, often) would be a bear. So... who knows. I'll have to see where the build takes me. This is in the development stages for now.
Anyways, this little(ish) tank had a lot of valves and gauges and stuff, all lined up on one side, which makes for a challenge when it comes to cutting them out and patching the tank. If there are 2 or 3 gauges and they've got some space between them, it's not too hard to cut them out and weld in square or round patches. But these are really too close together for that, which means... things are a bit more complicated.
Here's the tank once I used the plasma to cut a hole in the head after filling with 30 or 40 gallons of water and dish soap.
Cutting out a large section like that presents its own challenges. Namely, structural integrity, but this isn't a weight-bearing structure or anything like that, nor will it be a pressure vessel ever again. BUT, when you cut out large pieces, it relieves some of the stresses in the metal, and adds new ones when you weld in a new chunk. Heat affects things, as well. The concern is what's going to happen to it when you cut a door into it? Well, the door is going to be on the opposite side as these gauges, but the stresses and heat can still affect it from the other side anyways. And you have to think about the weld seams from when the tank was originally rolled from a single sheet of steel and welded together. The longitudinal weld seam on this tank is along the bottom, as it sits in this pic. You really want your door to be far away from the weld seams, as that is where the most heat and stress have been applied, but I'm also about to create MORE weld seams in it, too. Oh well, not much you can do about it but deal with it, right? Right! I can work on reshaping a door (or the tank) if it pops or relaxes once it is cut out. Just gotta do what you gotta do.
So... first I took my Dewalt slicer to it, but in trying to get as close to the valves as I could, I was worried about lateral stress on the cutting wheels and a wheel shattering and putting my eye out or something, like in the movie A Christmas Story. Definitely didn't want that, so I ended up moving the tank into the shop and cut it free with my new plasma cutter (Primeweld CUT60). Here it is after cutting it free.
Then to decide how to make the patch. Hmmmm...
I could have just cut some steel plate and welded it in place, but that would be flat, and wouldn't match the contour of the rounded 30" diameter tank. For small patches, sometimes this is ok, but if you want it to look decent afterwards, it's much better if you contour your patch. But how to do that?
I decided to use my band roller, which is a handy tool, but I can only roll 3" strips at a time. First rule of getting good cuts with plasma is meticulous layout of your cuts, and then using a guide to run your torch along. This took some effort to get set up, but it is worth it to get good material to work with. Have to mark where you want to cut, and then calculate the offset from your guide to the opening on your plasma cutter and factor in the kerf thickness as well. Then how much you're going to take off with the grinder flattening it out and cleaning it up afterwards, as no plasma cut is perfect unless you're using a CNC plasma table - or at least mine aren't! Here is one of my cuts laid out and ready to go.
Luckily my 2 pieces ended up exactly 3" wide, then I used my roller to bend them little by little and matched them to the curvature of the tank itself.
Now marked to cut into sections 5 1/8" long, which is the 'height' of my opening in the tank.
Cut section beveled to allow for better welding.
Coupons also beveled and aligned to make up my patch:
Tacked together:
Then tacked together on front, cut loose and heavily tacked on backside to prevent warping of my patch when I fully weld it all together.
I took it all outside and ground down all the tacks to be smooth on the inside of the tank. I'll need to trim it down some, as it's about an inch too long (I wanted to give myself some 'wiggle room' for error), then clean up the bevels, and weld it all in place, probably tomorrow.
So this is the method I used for patching this tank. Hopefully it'll all come out well once I get it welded in and grind everything down and it'll look pretty close to the original tank contour.
We shall see...
More to come tomorrow or later in the week.
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