Large diameter,lined and thin wall pipe design 1

[simplemath]

Please refer to thread292-209303:

http://www.eng-tips.com/viewthread.cfm?qid=209303&page=1

We deal with large thin walled pipe with lining.
D = 60", t = 0.5" , D/t = 124, A516 Gr70 plate rolled, 30 psi,650 F, B31.3.

I want to continue this thread and ask about vacuum rings.
We do not have vacuum load case(connecting two vessels without isolation valve. None of vessels are designed for vacuum.)
Rings are for extending the span due to lacking of supporting.(Caesar sustained loading gave 91% of stress range.)
Since ASME section talk about rings to counter full vacuum, I would like to ask if any method of calculating the required rings size and span for the purpose of increaing the pipe span.

As I mentioned above , pipe has lining inside. The resco castable lining would increase the section modulous and thus reduce the pipe sag.
I would definitely use revised modulous the calculate the expansion stress and load on nozzles, but is it ok to take lining stiffening into account to determine the primary stress?

Thanks in advance.


--It boils down to simple math--

 

[BigInch]

Vacuum rings really wern't intended to work in the axial direction for the purposes of reducing bending stress and their effectiveness in the axial direction would be doubtful at best. Rings increase radial stiffness. I would suggest that if bending stress is the problem, you should work on reducing that directly.

"323.4.3 Cladding and Lining Materials" would seem to indicate that linings cannot be taken into consideration.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[DSB123]

I would not consider the internal liningto provide additional strength to ruduce stresse. With lined piping the problem with large bore, thin walled piping is the limits you set for the deflection of the pipe wall such that the castable lining is not damaged/cracked.

As Biginch says circumferential rings are not normally used to increase pipe spans and would not help for axial bending apart from tending to prevent the pipe from buckling in a radial direction due to high axial loads. Suggest to look to limiting the defection of the pipe wall to prevent damage to the lining.

 

[simplemath]

Appreciate your clarification on this.

DSB123 and biginch:

Do you know how can I get the limit of pipe deflecction that will prevent lining damage? RESCOCAST 17EC is the lining material. The modulus of rupture is 1500psi.Use this value as allowable bending stress to calculate the max deflection. Is it correct?

The max deflection value is small. I will confirm if the modulus I remember is correct.

Thanks.

--It boils down to simple math--

 

[JohnBreen]

You should refer to AWWA Design Manual M-11

http://engineers.ihs.com/document/abstract/FIPWGBAAAAAAAAAA

You might also get some insight on large diameter pipe saddle design by referring to the Lincoln Arc Welding manuals by Blodgett.

Another design manual that you might want to look at is the manual titled "Welded Steel Pipe". The American Iron and Steel Institute (AISI) has published a steel pipe design manual titled Welded Steel Pipe Revised Edition 2007. The manual focuses on the design of steel pipe up to 240 inches (6,000 mm) in diameter under either internal or external pressure. It is available for downloading free of charge at AISI’s Web site (

http://www.steel.org).

You have several issues to consider. The relatively heavy weight of the liner will generally cause the design to require shorter spans between supports. The supports may have to be saddle type so that the load is distributed over a greater area on the pipe OD. The STIFFENER rings will extent the possible length between supports because the rings will keep the pipe round in cross section - the pipe must begin to collapse (form a plastic hinge) by first ovalizing. This is described in some of the reference mentioned. But obviously, there are limits.

With your diameter to wall thickness ratio exacerbated by the additional weight of the lining you can no longer design the "pipe" as a beam as the local membrane stresses cannot be predicted by beam theory. Basically, you would use the same approach used in the design of horizontal vessels. The stiffening rings at the vessel supports maintain the shape (reduce ovalization) and allow longer spans between the support saddles.

Regards, John.

 

[4Pipes]

Refractory lining for high temperature, whether by brick or by gunning, is a combination of science and magic. I have seen some very serious problems when only science has been used. You have correctly identified the problems but getting the answers is another matter. Oftentimes even the refractory supplier cannot give the full answer. The answer often includes in-house guidelines from years of trial and error. What cross sectional deflection can be accepted? I don't know. All I do know is that you need to get it right. You will need to be talking to material suppliers, installers, users and anybody else you can think of. Relying on stress might not be straight forward given that the material could be in compression when hot.
Best of luck.

 

[JohnBreen]

You can download the AISI manual "Welded Steel Pipe" free at this Internet address:

http://www.steeltank.com/Portals/0/pubs/Welded

Steel Pipe 10.10.07.pdf

John