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Door Sheet Welding Procedures

Monday, March 22, 2010   By: Jason [793] 0 Stars
Does anyone have suggestions for how to fix this? The tank buckled in above the corner of the door sheet see the photo. This is the welders first door sheet. Currently the plan is to re-cut the door sheet and hope the tank resumes its original shape, then re-weld. What is the procedure for welding the sheet? He used an alternating method all around little on top, little on bottom, little left, little right, repeat.... Comments appreciated.



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Monday, March 22, 2010   By: DavidR@Fast.net [39] 5 Stars
I am not near as good at this kind problem as REAL tank builders. But if you asked me I would say:

Remove and toss this door sheet.
Then hope you can pull the distorted/deformed shell back into position.
Brace the shell vertically and horizontally
Fit and weld the new door sheet with welder who knows what they are doing:
1. Weld one vert completely
2. Push the sheet out and weld the second vert it will pull back in as is cools
3. Weld the horizontal seam
4. Weld the round seam
There is no guarantee on this type of work, it takes a better boilermaker to weld in a damaged thin plate door sheet then just about any other type of door sheet.

Good luck!

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Tuesday, March 23, 2010   By: JDM [672] 3 Stars
The dreaded Doorsheet ..... oh what a tangled web we weave.

Never put someone on a doorsheet that has no experience of doing it.

You should cut that doorsheet back out and if you are lucky enough it might pop back into position but it would be doubtful. From what I can see in the pic the buckle is running up into the 2nd ring. If it doesnt come out when you cut the doorsheet then you will need to order some more plate and go from the small doorsheet to cutting it up the the round seam and going through the buckle to a good spot.

How thick is the shell plate ? I am assuming quarter inch.

There are many ways to weld in a doorsheet but I have found this to be the best for me.... some will agree ... and some will disagree.

Cut out the doorsheet with the smallest possible cutting tip.
Make sure to store the doorsheet where it can hold the natural curve of the tank
Hang doorsheet by fitting up one vertical ........with as small a gap as needed for the welder
Weld that vertical
Fit up second vertical ......small gap again
push as much slack as you can on the roundseam and cornerweld.... away from tanks center
weld second vertical..... the slack you gave it on the round seam and cornerweld will have mostly disappeared by now
Fit up round seam .... weld outside first .... depends on how the doorsheet is looking to determine welding e.g. center - out... ouside - in ... backstepping blah blah blah. normally it would be outside to center for me.
Now go inside and weld roundseam..... start in center and weld out .... this is whats going to round your tank out.... again you always have to evaluate the tank and how its looking to determine what comes next...

Doorsheet and insert welding is a art.

Good luck ..... YOU ARE GOING TO NEED IT.

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Tuesday, March 23, 2010   By: BABRTs [53] 5 Stars
The chance of you pulling this out and it looking good are 50/50.
Slim to none.
Some do not think on thin plate key plates need to to be used. A really good fitter can get away with not using key plates, but then you did not have a good fitter.
Some do not think on thin plate the opening should be supported with channel or I beam. I do and insist on it,
Re-using the cut out has to done carefully as the heat of cutting and re-installing tends to flatten the cut out unless it is braced with rolled angle before cutting.
To attempt to fix this, brace the opening and cut the sheet out and toss it. Have a new insert rolled to the radius of the tank. Cut down to the floor plates and cut 12 inches of the shell to bottom on each side of the vertical. This will allow the tub a little room to move and give you ac chance to relax the steel in the second course,.
Round out the shell and brace the top of the opening with rolled angle
Fit the new door sheet. Keep the key plates in place. Leave plenty of slack in the top. This allows the steel somewhere to expand without pushing out the top.
Weld the verts, then the corners then the horizontal. Weld out the inside corner weld, diesel test then the outside.
I am taking for granted the tub is quarter inch. I have seen worse fixed, but it takes a really good fitter. Not the one that put THIS in.
Also, do not use 7018 for the welding. 5P out.

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Tuesday, March 23, 2010   By: JDM [672] 3 Stars
I agree with the bracing before welding .... but I wouldnt put the bracing on until I see if the buckle comes out ... otherwise you would just be trapping the buckle in place by bracing.

Just a thought.

But again I dont think this one is coming out with out inserting a bigger doorsheet.

I did notice that the pic shows that the doorsheet was not cut down to the bottom after BABRTs mentioned it ... Take it to the bottom plate. I also would not gamble ... I would use keyplates .... and yes i agree always cut back the extra foot on cornerweld and horizontals too if they fall in the roundseam.

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Tuesday, March 23, 2010   By: BABRTs [53] 5 Stars
Sorry, I just assumed. Get the buckle out first.
Two years ago I had a welder putting in a manway insert on a riveted tank. I asked him if he had worked on a riveted tank and put in a large insert. He let me know real quick he could weld a beer can to a ceder post and do it fast. I told him put it in right.
He welded it out in one afternoon. And it was braced. I did not see it that evening but saw it the next morning. One corner had pulled in.
Called the superintendent and told him to cut it out.
Welder wandered up in the middle of our conversation and was bragging on how fast he welded it. I thought the super was going to put a slag hammer in the middle of the welders forehead. He hit the gate. Took them two days to get the shell round enough to fit the new manway insert in. They lost the insert, and the manway. The fool was putting on the final pass on the outside of the manway neck when he got run off. But he was fast!

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Tuesday, March 23, 2010   By: DavidR@Fast.net [39] 5 Stars
I dont believe that the cut-back on the corner and/or horizontal seams is an option. See API 653 Figure 9.1 and Note 3

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Wednesday, March 24, 2010   By: Jason [793] 0 Stars
I want to thank everyone for their comments and give a status update.

Here is the plan: An experienced contractor has been retained to cut a larger opening and install a new door sheet. They are going to cut all the way to the bottom and up into the second ring with horizontal relief cuts at the change in plate thickness and at least one foot on each side of the original door sheet details per API 653 fig 9.1. The tank will then be straightened if needed. A new steel plate will be rolled and installed in the opening. Tank shell is 1/2 on bottom and 5/16 on second ring. I will post another update when it is done.


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Thursday, March 25, 2010   By: EX-WELDER [269] 1 Stars
1. always install stiffeners before cutting out original plate for door sheet especially thinner shell plates
2. depending on scope of repairs client may not want door cut all the way to the floor to prevent hydro of tank
3. as stated above fit and weld first vert outside, fit and weld second vert w/ both horizontal seams pushed out after completing verts fit upper horizontal seam and weld outside followed by inside , fit and weld inside corner weld or bottom seam last.
4. never let a rookie learn to weld doorsheets without experienced help, they need to have someone there who knows how to work key plates. granted every welder needs to weld door sheets eventually but without proper training or experience you can have a real problem on hands as you can see!

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Tuesday, April 06, 2010   By: Ram [801] 0 Stars
Dear Bobrts , I was wondering what could be your reason Not to use Low h2 eletrode E-7018 or E-7016 and reco for E-6010
Could you please detail me the reson for my own understanding ?


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Wednesday, April 07, 2010   By: Ram [801] 0 Stars
What is the best and appropriote electrode that can be used for door sheet welding ?? I understand E-7018 is not prefered


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Monday, April 05, 2010   By: Jason [793] 0 Stars
Update: The door sheet and approx. 1 of tank wall around the sheet were removed. The buckle in the tank came out without persuasion after the opening was cut. A new steel plate was rolled and fitted to the opening and the old steel was discarded. The vertical welds are about 2/3 complete at this point. As you can see, things are looking good so far.

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