Minumizing PV wall Thickness 3

[liondeath]

Hello to all,
bare in mind this is my first time to post on this sight, I'm still a new member.

I have a horizontal vessel I am trying to quote for a customer. The pressure is 1425 psi, Temp of 350ºF and an O.D. of 28".

When I run Calc's thru Compress, it chooses a wall thickness of 1.252", as the min.. Using SA106-C SMLS as the shell and SA516-70 for the heads.
With it being that thick, I'm having a hard time finding vendors that will quote me on the heads, and the shell has to be made. So in order to cut down on cost, I'm trying to lower the wall thickness by using a different material.
I've tried running Calc's with SA516-70 for the shell and heads, but it will not lower the wall thickness enough(1.125" Nom.)

Does anyone have any suggestions as how I could lower 'T'?

Thanks in advance!

 

[SnTMan]

liondeath, welcome the forum. I'd say:

"Bear" "site", lower "P", higher "So", smaller "d", less "CA" (if any). About it. When designing the larger vessels for over one-thousand psi, one often has to bite the bullet and not fab from sheet-metal.

BTW, seamless pipe not usually available above 24 OD, it would most likely be a roll & weld (plate).

Care to mention a Code of Construction?

Regards,

Mike

 

[liondeath]

Thank you for the response Mike. I apologize for my lack of information & spelling.

It will be per ASME Section VIII, Div. 1.

"CA" is .125" as per client specifications.

I haven't heard anything back from my vendor to have a piece of plate rolled. But when/if I get something back from them, I'm still stuck wondering how am I going to get the heads made (2:1 Ell.), as all my other head vendors (thus far) have declined to quote.

-Joe

 

[SnTMan]

liondeath, you should be able to get such a head, you in the US? Any number of manufacturers available.

Speaking of your client, has he specified CS? If so, you're most likely stuck with it. Are / can you full RT to up the efficiency?

Got any openings, such as nozzles? This may dictate added thickness.

Lot to know, not much to go on...

Regards,

Mike

 

[liondeath]

I'm in US.

With already four of my vendors declining to quote, it has got me worried if I will get one at all. And I don't want to lose the opportunity to get this work. But if I'm stuck with the thickness, I'll start making some phone calls

The client has sent me some drawings that specify CS and RT-1. The Tan-Tan is 120".

There are (2) 6" openings and (7) openings NPS4 and smaller. By making the shell SA516-70, I was able to pass calc's without PWHT. But, and I have not found out why (yet), the heads of the vessel still have to be impact tested to reach MDMT, which is -20ºF.

Is there a stronger CS plate that I can use in lieu of the SA516-70?

Thanks!
-Joe

 

[SnTMan]

liondeath, if there was a plate stronger and more readily available than SA-516-70, that's what everyone would be using

You might gain marginally with something like a 1 1/4 Cr such as SA-387-11 Cl 2, but there would be a number of unpleasant downsides. There some strong stainless materials and some really strong non-ferrous materials, but not at anything like CS pricing, besides which, your client has specificed CS.

I'd say your software MDMT for the head is about right. SA-516-70, if normalized would go to -14 at 1 1/2 nom. BUT, you need to confirm it. I don't generally trust the softwate on MDMT.

Might try these vendors (I have no affiliation)

http://www.artcosteel.com/houston-blow-pipe

http://www.prescor.com/

If they can't, chances are they know who can

Good luck,

Mike

 

[liondeath]

Thank you so much Mike!

I'm going to give this a try.

-Joe

 

[wailunwu]

Try adding stiffening ring in compress.

FYI: Stiffening ring is usually for external pressure application but I am curious if it helps with the internal pressure.

Let me know.

Thanks,
Alan

 

[SnTMan]

No, it won't. You might have a look at the EQUATIONS.

Regards,

Mike

 

[liondeath]

Alen,

I've ran the calculations thru compress and it did not effect the shell thickness as ASME VIII Div. 1 does not account for internal pressure for stiffening rings. But it was worth a shot!

The below link has some information about design of stiffening rings for internal pressure:

http://www.eng-tips.com/viewthread.cfm?qid=363803

Thanks for the suggestion!

I'm going thru the ASME VIII Div. 1 code, and the Pressure Vessel Handbook (Eugene F. Megyesy) to see if I cant find anything.
Lots of Research, No Time.

-Joe

 

[marty007]

That thickness really shouldn't give you any problems for sourcing heads.

We've done a job recently using heads that were 3" thick. There are certainly suppliers, you just may have to look a little further afield.

Cheers,
Marty

 

[JStephen]

One thing I'll suggest is to try to work with your vendors a little more. For example, on the heads, have you asked them what the best approach is for a small high-pressure head? Have you contacted your local plate supplier to see what higher-strength plates are typically stocked for pressure-vessel use?

On the pipe- I think there are some high-strength pipes available in fairly large sizes for pipeline applications, but they may not be in ASME. Regardless, if you use a pipe material, you'll likely wind up having to buy 40' of it and keep the leftover 30' for the next 40 years until you can use it up.

Seems like there is a "Code Case" that can give thinner heads, but I'm not familiar with the details, anyone else?

 

[liondeath]

Thank you guys for your input.

JStephen,
I have contacted my "special pipe" vendor and she was unable to quote the large pipe.

As an update, I have been able to receive a quote back from my vendor for the heads. So that is no longer an issue.

Now I am pursuing a vendor to have some plate rolled, and I haven't heard anything back yet. But I am expecting something before Friday.

P.S.
I'd like to close this thread, but I'm interested to hear if there is any more information on this subject and a "Code Case"...
Also, I'm not sure how to


-Joe

 

[bpv66]

Take a look at Code Case 2695. It allows design by rule requirements in Part 4 of Section VIII, Div. 2 to be used to design components for a Section VIII, Div. 1 pressure vessel.

The Division 2 rules will in most cases produce formed heads that are significantly thinner than required by Div. 1.

There are a number of requirements in the Code Case that must be met but I think this may be applicable to your vessel.

 

[Afox88]

Lion,

As mentioned before, 28" OD seamless pipe is very hard to find. I would suggest a rolled SA-516 70 plate, which should be easy enough to find (the plate and the rolling). Unless you live in the middle of nowhere, you might even find a local place. There are even some CODE shops that will roll and do the longitudinal weld for you if that is an issue.

As for the head, Prescor (which was suggested by Snt; I also have no affiliation) definitely will be able to handle this. I have used them for much thicker heads.

I would not recommend switching to a low alloy steel. It is such a pain if its not needed. Not to mention the pwht requirements. You should at least be using spot x-ray at this thickness, even though it is not required by Code. The material and welding savings, of using the thinner plate would more than make up for the added x-ray cost.

 

[Riansyah]

Have you try to use Ring in Shell ?