What is the exact doubt? pipes with wall thickness as low as 3mm can be welded provided the edges can be properly aligned. Anyway for your 36" and 40" the thicknesses will be more than 1/2" (almost 3/4" onwards).

Why should be the pipe thicker than 1/2"?

I've done ducting that was larger than that and was around .050" (18 ga I think) without problems once I had the right machine set up for it.

I've also seen guys that could weld pop cans together without leaks before too!

Minimum welding thickness is determined by how good your welding equipment and operators are!

Thanks

But I am thinking in CS (API X65) pipe, OD 40" and wall thickness 5 mm. My question is focused to welding & handling issues for this pipe, because I have received some comments from welders that the minimum wall thickness for this pipe is 8 mm.

The wall minimum wall thickness is almost never constrained by the feasability of welding and should never be constrained by the strength of the weld itself.

a skilled TIG welder with a quality low amp machine (the miller 90 and the 120 inverters are awesome for holding a steady very small amp arc...however the service techs hate those machines) a pulser, a cheater lens and a clean workpiece can butt weld tubing like nivacrom or aermet easily that is only 0.5 mm wall thickness. with some practice, much thinner material can be joined even without using filler. The pulser i instrumental in thin wall material as you can set for full penetration and very rapid refreezing so quickly that the material has very little time to shift or fall away.

In most applications, the weak link will be the HAZ (heat affected zone) adjacent to but untouched by the weld

Benbenben

Thanks.

But I am thinking in CS (API X65) pipe, OD 40" and wall thickness 5 mm. My question is focused to welding & handling issues for this pipe, because I have received some comments from welders that the minimum wall thickness for this pipe is 8 mm.

dear questioner,

size of pipe is 40''/36'',wall thickness is much more,we have to calculate the strength of welded zone, so pipe can sustain the load during the pipe handling,how we make the groove and depth of welding which can sustain the load.

we prefer you can see the mechanical design book and calculate the strength of welded areas.

thanks

rcmandal

CE(I)

M-133566-3

GeorgeAB,

Your question originally asked about the minimum wall thickness for a welding process.

the answer provided is still valid for your original question.

you seem to not like the answers being given (have you perhaps lost an arguement or bet?) and are attempting to reject valid answers by claiming you are actually asking the very different question i will not attempt to paraphrase:

____'....What is the minimum wall thickness measuring 8mm, for material for which i claim credible sources have stated is 8 mm (even though i am unsatisfied with the answer and feel compelled to ask in this forum, the weight of these 'i-know-an-expert claims' should be considered reasonable by any person in the know)....and if you answer anything other than 8mm obviously don't know about this kind of thing.....'______

That is of course an entirely different question (statement, actually).

benbenben

There is a class of pipe called "thin-walled stainless", which is used in the water industry (others can specify the pipe class tighter). The wall thickness is around the 5mm mark, possibly lower depending upon pipe diameter. It welds readily.

You should limit your minimum thickness to a D/t ratio of 96. Codes vary so check your code or BoD. This ratio is chosen for general handling on site. Don't forget to crank into yor equation (Barlow's Formula) the corrosion allowance. I think you should be looking at WTs typically of 1/2 inch What is your product? Gas or OIl? What is your DP?

Good luck and keep posting, should you require additional info!

Stewie

dear mr George

the thickness of a pipe is decided on the basis of

a)mawp(maximum working ptressure)

b) water hammer force

c) the bending stress due to self weight and weight of medium

d) corrosion allownce

e) dynamic load due to vehicle and any other source

f) vacuum in the system

there are various codes ANSI,AWWA etc stipulate the minimum thickness requirement. as such there is no requirement from welding point of view. however thickness below 4mm is difficult to be welded. as a practicing engineer we have seen a ratio D/T more than 100 is considerd to be very thin cylinder and not structurally stable and may need stiffening inside.

p k mohapatra

PKMNTPC,

This really is a strange way you have presented for an engineer&especially practicing) to make decisions..

Starting Around half a century ago, Atlas missles were fabricated using stainess steel sheets , as thin as 0.018" wall thickness, bent to form a cylinder 10 feet in diameter. the cylinder was pressurized and withstood stressed of rocket launched travel to space..

Technology has even improved some since then. it is not all that difficult to weld material that is quite thin, and pressurized cylinders easily exceed the 100 D/T ratio and are still strong enough to make it to space launched by rocket.

Benbenben

Thanks very much. You are good man Mr Charlie Brown!!!!

Check out Trouvay & Cauvin ( Bluebook).

Hope this helps.