i want to learn to weld...

In Virginia to register a homemade trailer you fill out a form (downloadable from the web), send it and the fee ($5) into DMV to receive a trailer VIN. Install the VIN per instructions, get a Law officer or EMV rep to inspect trailer and say it's OK and sign form. Take form to DMV and get title.

Now if the vehicle needs brakes (GVW of 3000 or more) then the trailer must also be state inspected - as does any non homemade trailer.

 

This is my last big repair job that I will take on. I am posting this with all my mistakes so you all out there can see what to do and what not to do. I will include pictures later.

When asked to help I dont know how to say no.

History; A Compressed air tank belonging to an old dentist friend starts leaking. I do an on site inspection and find a stress crack at one leg.

The tank appears to be solid and no rust showing on the edges of the crack.

My friends(yeah-sure, I'm am 30 years old at the peak of my productive career:-laf) suggest I try to fix it in place! BUT, I am not able to lay on the floor anymore and do the out of position prep and welds. I have to work on it in my shop.

With some help from mutual friends that run a construction company, we were able to get the tank onto a Truck(A Dodge with a Cummins, no less) and transport it a few miles over to the shop.

It stayed in the truck during the work. It is mounted on a pallet so there was no metal to metal contact with the truck body. We were very careful not to ground out through the truck to protect the truck electronics.

Now the point I am trying to make here; This is an ASME code pressure vessel. Using the proper techniques, it can be repaired.

Polish off the paint and locate the ends of the crack. Drill out the ends of the crack to keep it from propagating. Grind out the metal around the crack in the shape of a u groove with a thin root that will be burnt out. There will be contamination from rust and compressor oil, inside the tank. SMAW and GMAW are the best options for repair. I tried TIG at first and wasted 2 hours fighting spitting and tungsten electrode contamination. Took a break for a couple of days and went back with 3/32" E7010G HYP rod and SMAW process. I was able to blow through the contamination, grind out porosity and tie everything together with a solid root pass and hot pass with the E7010G rod. Now the fill and cover must be done with Low Hydrogen, 1/8" 7018 low moisture absorbing . Even that was touch and go. After 4 hours of fighting with old rod that was stored in sealed plastic bags, I was able to get part of the welding completed. However the worst part of the weld needed rod that was in better shape. So I took a hand full home to bake out in my oven. The 7018 has been in there since 1830 hours, last evening. Hopefully it will start easier and have less propensity to deposit porosity at the beginning of the weld that requires a burn through.

Every weld action was and is proceeded by a preheat with a torch. After the weld is completed, I will post heat the weld area to about 400*F.

Heading over to the shop to get this show on the road. I hope this will be helpful to anyone out there that has a $4000 compressor, that requires some TLC vs the scrap heap!

GregH

 

The ugly facts. Arc strikes and porosity. Repairs and labor intensive grinding. Shallow arc strikes were polished out. The deep digs were welded over with the 7018. This welding was done left handed(my off hand) and during a lot of physical discomfort. My days as a maintainence welder are over. A working shop could have done this in about 4 hours(@ $90/per hour plus materials). I have 11 hours in this over 5 days. Had to take time off to recuperate. I love to weld but this was a killer for me!

Feel free to ask questions and criticize the job. Thats how we learn!

Heres some pictures for your amusement!

GregH

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Heres a few more of the position, equipment used and two of the arc strike repairs after completing the fill weld on the left side with two stringer beads. I have polished/ground areas with suspected porosity. I used the tarp to catch sparks from grinding. There's a diesel fuel tank directly behind the tarp as well as very high fire danger in the area. A wild spark could start a forest fire in this tinderbox!

GregH

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The last arc strike repair. BLAST IT(CURSING) Of all the amature screw ups I could have made, here is the worst. Right on the forged end cap. I preheated the area and welded with 7018. Had to do it twice because the first rod gave me nothing but pin holes. I am using a 1/16" tungsten to check for undercut. It is within code requirements. So here is the repair. All it needs is to be re set and pressured up. That will determine if the weld was worth the trouble.

In hind sight? I should have swallowed my pride and said no:{!

Secondly, looking back, I should have gone to the welding supply store and bought a brand new sealed 50# box of 3/32" 7018! Old low hydrogen welding rod just don't cut it for a pressure or high stress application. Moisture absorbed during cold storage deteriorates the 7018 rod coatings over time. This rod was 5 years old.

Heres what we are dealing with, 125#/ sq in pressure. The drum is 4' long and about 2' in diameter. This equals 8 sq ft X 144 = 1152 sq in.

The end caps are about 6 sq ft area each so we have 12 X 144 = 1728 Sq inches. So add 1152 +1723= 2880 X 125# and you get #360,000 of stored energy! The numbers are not exact, but just to give you an idea of the potential store force in a compressor tank.

GregH

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Wow. Here's what I think is great about that story.

First, Greg is a professional. The fact that even he can make mistakes and fumble things here and there but still persevere and finish with a quality job is inspirational to an amateur hack like me.

Second, despite the struggle, the end result looks great! The ability to succeed despite adversity is the mark of a true craftsman.

Bravo, Greg, and thanks for sharing. And I don't believe you for a second that this is your last big job!

-Ryan

 

Well the upside to this is that the Compressor was installed and it works fine! No leaks and no further cracking at the repair location.

It took me 11 hours to do the repair. With new welding rod in the shop, the time could have been cut in half. Grinding out flawed weld deposits from deteriorated rod was very time consuming.

My conclusion for all to learn from is; Do not short cut yourself. Use good materials! Use old rod for practice. Buy fresh rod in sealed cans for high stress applications! The added time to make repairs adds to the weldors stress level. This is supposed to be FUN!

GregH

 

Hi Guys, this is a fantastic thread. I just caught onto it and have been catching up. I like reading about everyone's different experiences trying to do the same thing. I'm not a pro metalworker by any means, but I have been exposed to various process by being lucky to work in a fairly serious landfill shop where there were guys willing to share. One of the "old timers" long retired gave me reams of paper to keep at and read on his way out, and I still have some of it. One thing in there that I haven't seen so far here is a poem about compressed gas tank safety. I found a newer version and here it goes;

A SLEEPING GIANT



I am a compressed gas cylinder.

I weigh in at 175 pounds when filled.

I am pressurized at 2,200 pounds psi.

I have a wall thickness of about 0. 25”

I stand 57 inches off the deck.

I am 9 inches in diameter.

I wear a cap when not in use.

I wear valves, gauges, and hoses when at work.

I wear many colors and bands to tell what tasks I perform.

I transform miscellaneous stacks of materials into glistening

ships -- when properly used

I transform glistening ships into miscellaneous stacks of material

when allowed to unleash my fury unchecked.

I am ruthless and deadly in the hands of anyone careless or

uninformed.

I am too frequently left standing alone on my small base -- my

cap removed & lost by an unthinking workman.

I am ready to be toppled over -- where my unprotected valve can

be snapped off -- and all of my power unleashed through

an opening no larger than a #2 pencil.

I am proud of my capabilities - here are a few:

I have been known to jet away faster than any AA fuel

dragster on the NHRA circuit - over 800 mph;

I smash my way through brick walls with the greatest of

ease;

I fly through the air for distances of more than half a mile;

I spin, ricochet, crash, and slash through anything in my

path;

I scoff at the puny efforts of human flesh, bone, and muscle

to alter my erratic course;

I can penetrate a pickup truck from end to end;

I have been known to blast my way through four 14-inch

brick walls before running out of pressure.

My escaping oxygen exhaust burns everything in its path.

I can, under certain conditions, rupture or explode -- then,

you read about my exploits in the newspaper.

You can be my master ONLY under my terms:

Full or Empty, be sure my cap is on straight and snug;

Never, NEVER leave me standing alone;

Keep me in a secure rack or tied so that I cannot fall;

Treat Me With Respect, I am A SLEEPING GIANT



​

If I knew where it originated, I'd give credit.

 

GregH, years ago I was working at a general engineering shop, repairs, ornamental and structural steel, I was sent on a Friday afternoon to repair a tank, I believe it was at a dry cleaning shop or some other type of business as it was in the center of a shopping area in town, I was told a plumber had tried to repair it but job too much for him, but he was there to explain the situation. When I got there he had covered the split with a patch about 3 inches by 6, and tried to braze the patch to the tank. The tank was made of gauge steel so very thin, and the working area was very clean, brightly painted. I was concerned of probable explosive liquids, thus highly inflammable vapors but was told it was safe for open flame, so the amount of brass deposited on the patch seemed it was safe to weld. I told the plumber I was going to take off the patch to view the split. He was pleased to leave, so I used the oxy-acy heating tip to melt off the patch, plus much of the deposited brazing material, then used the grinder to clean everything up. I was told the tank was low pressure, but being the split was not in an area that could be affected by stress, plus not work fractured or work hardened it was probably not pressure that ruptured the tank, a fault in the sheet was probably the cause, as the area around the split was not deformed. Trouble is, often you are not told the truth about anything of why something failed, they want the job done as cheaply as possible, plus they do not want to draw attention to the authorities, and or health and safety etc. and or regulations. I lightly veed the split, it was around 4 inches long, actually just brushed it with the grinder to assure clean metal, deposited spots of weld at intervals then ran a bead over it. I told the person in charge to remember it was a repair with no guarantee, and as there was no sign of stress in the split, the tank was flawed, and better to get the tank replaced as there could be other flawed areas. On returning I told the person who sent me what I found, what I done, and what I said to the person in charge.

 

Very Good thread. Lots of good info and I did get the book already, now time to start practicing and ready. I just got a Mig from Summit the 160 model and a Lincoln Tomahawk 625 plasma cutter. Sick and tired of trying to find out where I can get some relatively little jobs done locally, we are 10 miles from the nearest small town so I said frik it. Spent the money for the equipment now I need to learn how to do it. This is going to be my 1st project for my freestanding roof for the lawn mowers, trailers, and log splitter. put one of these in each corner plus middle brackets that go up to support the centers, similar to the 1st one I did in Anchorage.

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GREAT Idea! If Ya have any questions? Ask Away!
If I don't jump on it, right away, I am sure there are plenty of others with the skills necessary that can also help You on Your way!

GregH

 

Crazy Horse- how is that lean to type building secured to the ground? Is it literally 'freestanding'?

 

Looks good but the post in front of the walkway serves no structural purpose. It's only supporting the end rafter.

The only way to learn to weld is to actually weld. Buy some scrap steel and lay down some weld. I cut a lot of practice welds to see how good they are.

My favourite accessory is a metal band saw. Way better than a chop saw.