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lito
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Join Date: Jun 2011
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Cutting Safe Distance From Weldments

11/08/2012 12:21 AM

Dear Gurus,

Hi! we are in a project of disassembling of a large steel tank which shall include cutting using plasma.

Can anybody help to provide a safe distance from the weldments/joints to do the cutting without jeopardizing the metallurgical properties of the metal?

Is there any standard/s that this can be made as reference?

Your help would be of great help.

Thanks.
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Tornado
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#1

Re: Cutting Safe Distance From Weldments

11/08/2012 1:04 AM

This is only rule of thumb, but IIRC a safe distance is the greater of 2 inches (50 mm) versus 2.5 time the width of the existing weld. If you search on "heat affected zone" (HAZ) of welds, you may find better information.

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lito
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#2
In reply to #1

Re: Cutting Safe Distance From Weldments

11/08/2012 1:25 AM

Thank you Tornado..does it mean, no internationally acceptable standard/s stating this rule?
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Tornado
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#3
In reply to #2

Re: Cutting Safe Distance From Weldments

11/08/2012 1:38 AM

I don't know, but I doubt that there is a universal standard.

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lito
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#4
In reply to #3

Re: Cutting Safe Distance From Weldments

11/08/2012 2:01 AM

OK, thanks much for the info.
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Darolim
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Join Date: Nov 2012
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#14
In reply to #2

Re: Cutting Safe Distance From Weldments

11/09/2012 10:18 AM

Please check page 29 of this material, which might give answer to your question.

www.http://www.iacs.org.uk/document/public/publications/guidelines_and_recommendations/pdf/REC_47_pdf193.pdf
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PWSlack
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#5

Re: Cutting Safe Distance From Weldments

11/08/2012 3:27 AM

Why are the metallurgical properties of great interest in a vessel cutting operation?

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lito
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#6
In reply to #5

Re: Cutting Safe Distance From Weldments

11/08/2012 4:47 AM

we intend to rebuild/reweld the vessel.
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PWSlack
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#7
In reply to #6

Re: Cutting Safe Distance From Weldments

11/08/2012 4:50 AM

So, why plasma-cut it in the first place? Why not cold-saw or use a grinding/cutting disc?

Does this tank have a pressure rating? If so, then scrapping it and starting with virgin metal would be a far better bet.

What fluid is going inside the tank, its temperature and pressure?

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lito
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#8
In reply to #7

Re: Cutting Safe Distance From Weldments

11/08/2012 5:06 AM

cold saw, grinding/cutting disc is not possible.

other clarifications not relevant already.

thanks.
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ronclarke
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#13
In reply to #7

Re: Cutting Safe Distance From Weldments

11/09/2012 9:18 AM

Why not cold-saw or use a grinding/cutting disc?
Time/cost.

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jmmyadam
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#9

Re: Cutting Safe Distance From Weldments

11/08/2012 9:41 PM

You can refer to this link:

http://www.weldguru.com/welding-safety.html
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john kingham
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#10

Re: Cutting Safe Distance From Weldments

11/09/2012 12:39 AM

Dear Sir,

My comments to the following inquiry. I was involved in a similar restructuring & repair work to a large petroluem tank 2 years ago in most probably similar to the situation you are in now.

My solution to cutting the 15mm steel plate was by using a very high water jet cutting machine. If I can remember the pressure rating was somewhere between 800 to 1000 bars and I managed to hire the unit from a Ship builder I knew. All I needed was a siphon pump to discharge the water out during the cutting procedure. The main 100hp electrical motor driving the piston pup was placed outside and I need a 5000 gallon tank of water on a trailer for the main feed.

Some bracket modification work was required inside the tank to hold the water jet nozzle in position with one operator inside during the cutting process. Communications by walkie talkie for a 2nd man at the opening overseeing the cutting operations to the main pump operator.

NO HEAT - No Metal Fatique. Clen cut is all I needed.

Hope this helps.
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Mechanicalmark
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#12
In reply to #10

Re: Cutting Safe Distance From Weldments

11/09/2012 9:13 AM

Great answer especially for a first timer! Welcome to CR4!
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lito
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Join Date: Jun 2011
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#15
In reply to #10

Re: Cutting Safe Distance From Weldments

11/19/2012 12:58 AM

Water jet cutting is actually top on the list, but we're finding a way to minimise cost and plasma comes next.

Thanks very much:)
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unclefastguy
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#11

Re: Cutting Safe Distance From Weldments

11/09/2012 8:15 AM

Cover the area you want protected with weld blankets and/or use a heat sink to direct heat away from the area you want protected. You can find them at any weld shop or hardware store.

UFG

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Users who posted comments:

Darolim (1); jmmyadam (1); john kingham (1); lito (5); Mechanicalmark (1); PWSlack (2); ronclarke (1); Tornado (2); unclefastguy (1)

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