using pipe for vessel shell 2

[sksmechanical]

just ran calcs for vessel shell thickness which 36" OD sch. 40 pipe can be used. question is what sizes are seamless pipes manufactured to? also if out of range what sizes are erw pipes manufactured to? or will this have to be fabricated as a can of itself?

 

[TJHAK]

Seamless is typically much more expensive these days, but you should be able to find it to whatever wt you require.

ERW pipe can be manufacutred to whatever WT you require as well & is usually more cost effective, if the code allows its use for your application.

The grade of material will affect the process of manufacture and availability of the material.

 

[rneill]

I would typically source seamless pipe to a maximum of 24" diameter. Beyond that, in my experience, it is difficult and/or very costly to obtain and I would typically default to a welded pipe product.

Welded pipe is available as ERW but I prefer to specify double submerged arc welded pipe (DSAW as opposed to ERW) pipe for these large sizes as I believe the overall quality will be better.

DSAW pipe is often ordered as ASTM A671 material (though some people order A672 which is very similar). The grade will correspond to the grade of plate used for manufacture of the pipe. Grade CC60 would be A516-60 plate and Grade CC70 would be A516-70 plate. Different classes are available and I typically specify Class 22 which includes PWHT and 100% RT. Class 32 would be normalized.

You would have to check the rules of the vessel design code that applied to this project to see whether or not it would accept the use of welded pipe (either ERW or SAW) as the starting material for a vessel shell.

 

[racookpe1978]

Consider that the alternate to a (rolled and welded) seamed pipe construction is a (rolled and welded) plate construction method.

So, if a large bore "pipe" can be bought that meets the material spec for PV's at a lower cost than seammless "pipe" forced into that larger a diameter, you save construction time for the vessel walls.

 

[zdas04]

Also, seamless pipe has always had ovality problems in the larger sizes, a small out-of-round measurement in 36 inch pipe can be a real problem welding on fittings. The welded products are far more consistent.

David

 

[sksmechanical]

Now this is for my understanding (please excuse my ignorance)...So for seamless pipe it is generally manufactured with 24/26" being the largest OD size and anything larger will be a "special" order so to speak. Now I was told that erw pipe cant be used because of the weld seam....not sure what that means. But other than dsaw being a better quality than erw, are there any other advantages as to using dsaw other than erw pipe.

 

[pennpiper]

Now lets think about this a minute......

The original poster (sksmechanical) said that he (or she) is making a Vessel, right?
Now if this was to be a Vessel 10 feet in diameter it would be made of rolled "Plate" with welded seams or joints.

So,

What is the problem with using a rolled and "Welded Plate Cylinder" 36" in diameter?

As long as the correct weld method is used, I see no problem.

 

[rneill]

The only question in my mind is whether the weld procedures and examination completed on the rolled "pipe" would meet all the stringent requirements relating to welding in the vessel code.

I suspect that for DSAW the answer is yes (thought for EFW I'm not so sure) but I haven't confirmed this and a check would need to be done before proceeding with this option.

Since the pipe will be made following the procedures outlined in the ASTM standard, you likely have little ability to influence the weld method. Having said all this, there is the issue that for use in an ASME vessel, you would need to assure that the starting material meet an SA (ASME) Standard as opposed to an A (ASTM) standard. For example, ASME SA671 as opposed to ASTM A671.

 

[SnTMan]

Just get R&W plate cylinders

Regards,

Mike

 

[stanweld]

It may be cheaper to purchase SA-671 or SA-672 (both of which are relatively commonplace) rather than rolled and welded plate for the shell especially if the vessel manufacturer must subcontract the rolling and welding operation.

 

[moltenmetal]

If welded seam pipe is available at the correct size, wall and quality, it is usually cheaper than custom rolling and welding shells from plate. Pipe is mass-produced.

 

[sksmechanical]

thanks for the info gentlemen....and ladies if present.

 

[zdas04]

I've done pull tests on the longitudinal weld of ERW pipe and the weld is always stronger than the plate. Always. The plate yields first. The plate passes its ultimate tensile strength before the weld yields--so the ERW weld is a LOT stronger.

I don't question whether I can use a weld fitting, I just include it in the test. I don't question whether I can use a valve or a flange, I just include them in the test. Same with pipe manufactured to a standard like API 5L. The boiler code speaks to using stuff that was built to a standard and says it is OK.

I would use ERW for this project, count the money I saved, and never look back.

David

 

[GenB]

no coments! I cannot find SAW pipe mfd by a pipe Company for ASME Code construction.

 

[BCbrad]

Just a reminder; when calculating required thickness using pipe as a shell, you need to consider the pipe undertolerance outlined in UG-16(d). For ERW I believe it is 12.5%.

 

[GenB]

Gentlemen, if you find erw pipe greater than 24in. or even welded pipe w/legal ASME spec I need to know. I'm very interested.
GBC