PA160 STH unboxing!

[Arc weld]

Try working with a 2nd year apprentice who already knows-it-all. :mur: I was supposed to be a shop supervisor(a long story) at a place that had kind of a secondary shop to the side of the main shop. They built box shaped incinerators from 1/4" plate about 5' square and lined them with refractory cement. The guy acting as lead hand for these was a 2nd year and too full of himself to listen how to make a proper corner joint. He was putting one plate inside the other and welding the inside and outside of the corners. In his mind it was stronger this way. He took real offence when I suggested fitting inside corner to inside corner to leave a perfect joint for a full strength fillet weld from the outside!:talktothehand: Anywhere else they would have told him to shut and listen or hit the road. I heard after the fact that the guy didn't like working with me. What's even sadder is the foreman before me didn't have a clue either. It boggles the mind sometimes how some people in the trade don't even know the most basic stuff.

 

[Shield Arc]

He took real offence when I suggested fitting inside corner to inside corner to leave a perfect joint for a full strength fillet weld from the outside!

Well I'm no engineer, far as I can remember I've only been on 1 train in my life.
But that is exactly how I would have done the corner joint. Unless the prints said otherwise.

 

[IslandTractor]

Well I'm no engineer, far as I can remember I've only been on 1 train in my life.
But that is exactly how I would have done the corner joint. Unless the prints said otherwise.

Not disputing you and Arc Weld but why would two lap joint welds be less strong than a single full fillet weld of a corner? I can see that it would take less time to do a single weld but is it also stronger?

 

[CNC Dan]

Not disputing you and Arc Weld but why would two lap joint welds be less strong than a single full fillet weld of a corner? I can see that it would take less time to do a single weld but is it also stronger?

I think he was agreeing with your way.

 

[joshuabardwell]

Not disputing you and Arc Weld but why would two lap joint welds be less strong than a single full fillet weld of a corner? I can see that it would take less time to do a single weld but is it also stronger?

Depending on the thickness of the material, the welding process used, and the skill of the weldor, the overlapping joint might lack penetration compared to the open corner. With the open corner, you can see the keyhole while putting it in, and by inspecting the back side of the weld. If you penetrate on the root and then fill the joint, you can be assured of full penetration.

Realistically, this probably was not a situation where full penetration was critical. The main advantage of the open corner method was probably just that a sound weld could be run with a single pass vs. two passes, cutting weld time in half. Maybe the guy didn't like the look of the back-side of a full-pen fillet and preferred to have two front-side beads where anybody could see them. Hard to imagine anybody would care what a joint on the inside of an incinerator would look like, though.

 

[IslandTractor]

Depending on the thickness of the material, the welding process used, and the skill of the weldor, the overlapping joint might lack penetration compared to the open corner. With the open corner, you can see the keyhole while putting it in, and by inspecting the back side of the weld. If you penetrate on the root and then fill the joint, you can be assured of full penetration.

Realistically, this probably was not a situation where full penetration was critical. The main advantage of the open corner method was probably just that a sound weld could be run with a single pass vs. two passes, cutting weld time in half. Maybe the guy didn't like the look of the back-side of a full-pen fillet and preferred to have two front-side beads where anybody could see them. Hard to imagine anybody would care what a joint on the inside of an incinerator would look like, though.

I understand your comments. I would think though that seeing heat effect on the other side of a lap joint weld would be pretty good evidence of penetration too. I imagine the single vs two welds is the strongest argument but was just wondering if there is technically a reason why a good single outside corner weld is any better than two good lap welds.

 

[joshuabardwell]

just wondering if there is technically a reason why a good single outside corner weld is any better than two good lap welds.

I can't really speak to that. I do agree that, on 1/4" material, you could probably get enough heat into the metal to be reasonably assured that you were getting full penetration. Only for somebody like a pipe weldor would you really need to be 100% sure.

I have done overlapping corners like that, and I am never really happy with the results if I don't bevel them, even on 1/8" material. Sure, the weld is probably penetrating at least half the metal's thickness, but I am always fighting to keep from melting off the corner of the on-edge piece, and the result never really looks neat. With an open corner, you have a nice valley to fill up with weld, and if you nip the corner, it doesn't look as bad (to me, anyway). So the open corner provides all the benefits of beveling without having to spend any time on the grinder.

 

[Shield Arc]

Man Joshua you are really catching onto this welding trade in the last few weeks!:thumbsup:
Reasons I prefer the corner to corner joint. A corner to corner joint with a slight gap almost certainly ensures 100% penetration.
When the two inside corners meet, or slight gap. The outside is a perfect trough for the weld to lay in. Easy as pie to make that weld! If at all possible, I would still make both inside, and outside welds! Then I know I'm getting 100% penetration!

 

[joshuabardwell]

I made a holder for my TIG torch out of some scrap tubing. The most fun part was manually grinding the square tube to fit the round. Also, a few more shots of some welds. I am having a lot of trouble feeding enough filler to avoid cratering. The Miller calculator suggests 3/32" for 1/8" material, but I'm using 1/16" because somewhere else I got the idea that's what I should have. I suspect I would be a lot happier with the larger filler. I have been half tempted to hold two rods together and feed them at the same time, essentially making a 1/8" filler, but I just try stabbing the 1/16" in faster instead.

 

[Arc weld]

The rule of thumb for fillet welds (this was a 90 deg. corner) is the leg length should be equal to the thickness of the plate to have the same strength. Over this is a waste and an overestimation of strength. If you get some penetration to the inside is good but as long as you get penetration to the heel, you'll have the strength. It also leaves a very smooth rounded corner that requires very little clean up and/or grinding. The time savings are more than half. Consider if there wasn't a big enough opening to get at the inside to weld it? Many tanks are built this way with just the outside weld.

There were no blueprints for these things. The owners of the company were too worried someone would steal their ideas. It was a real pain trying to build stuff without proper prints or even diagrams.