Rolled Plate vs. Forged Ring Method of Fabrication 3

[SteveBP]

For a reactor vessel in petroleum refining application with the following characteristic, is there a design pressure threshold which requires forged ring construction instead of rolled plate fabrication?

I assume that forged ring fabrication costs more and takes longer. Is this assumption correct ?

The design/operating conditions are approximately:
(1) 10 feet ID; 90 feet T/T
(2) 2 1/4 Cr 1 Mo, and likely to be 1/4 V modified
(3) Design temperature is 825 deg F
(4) Design pressure is between 1100 psig to 1300 psig, and the method of construction, cost and delivery schedule will influence the design pressure decision.
(5) The reactor will operate in high hydrogen environment, with hydrogen partial pressure in the 85 vol % range (between 900 to 1200 psig H2 partial pressure).

Thank you for sharing. Steve

 

[metengr]

For a reactor vessel in petroleum refining application with the following characteristic, is there a design pressure threshold which requires forged ring construction instead of rolled plate fabrication?

Not that I am aware of in relation to ASME Section VIII, Div 1. Obviously, the forged plate would have less directionality in comparison to rolled plate regarding tensile properties. However, in the grand scheme of things rolled plate would still suffice. You might specify cross-rolled plate for this application.

 

[unclesyd]

If you have any time constraints on your project you had better decide on a design to whatever code and get some preproject money to get the material on order. It seems as all the thicker plate is in demand and has very long lead times.

 

[TGS4]

Your biggest issue is going to be the capacity of the plate rolling. These reactors are going to be in the vicinity of 8-10" thick. One additional factor is that rolled plate is going to have a longitudinal weld, so the total number of weld-inches is going to be much more.

It also depends on which fabricator you choose. Some fabricators prefer plate, some prefer forgings. From my experience, it doesn't make a difference. Good luck with getting your deliveries this decade - Vanadium-enhanced 2-1/4Cr is a very long-lead item, as you will soon discover.

 

[SteveBP]

Thank you METENGR, UNCLESYD, and TGS4 for sharing. Especially appreciate the heads-up on the long delivery time.

We will get the "ball rolling". Hoepfully the plates will follow soon. Bye now.

 

[stanweld]

Hydrocracker Reactors were always designed to Div. 2. We never permitted rolled plate flanges for these reactors.

 

[stanweld]

I may have misunderstood your query. If you mean shell courses made from plate or shell courses made from ring forgings, either may be used. Some Owners prefer forged shell courses to eliminate the long seam weld.

 

[SteveBP]

Thank you Stan for the follow-up. I was getting a bit worried on the previous response. It was the vessel shell that I am most interested in. The forged ring shops all have significant backlogs and most certaily rolled plates will cut delivery time..

Thank you again and appreciate you sharing your insights. Steve

 

[LSThill]

Ballot 934B-01-07
Fabrication Considerations for
Vanadium Modified Cr-Mo Steel
Heavy Wall Pressure Vessels
Downstream Segment
API TECHNICAL REPORT 934-B
First Edition XXX 200X

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[ProcessSales]

Hi Steve,

I am working for a fabricator in Europe and ran this past our Estimating Director who advises:

QUOTE:

That pressure threshold is of course a function of the diameter ; for the specified 10 feet dia and material, that threshold will definitely well over the 1100-1300 psi range : in other words for the specified conditions, there is really no discussion, we would just go plate construction. We might need to start considering the forging only at 2000 psi design pressure or more.

If we go plate, we have 8-9 months lead time for both the conventional and V-enhanced construction options, with the latter requiring a longer fabrication time. Overall I see that 16-18 months could be a reasonable delivery time range ARO.

Should we go forging (but really no need at all in this case) price will be much higher, delivery time not necessarily higher, we'd need to check that with forgmaster. Anyhow not a consideration for this specific case.

As for the rest of the design conditions, no problem we are comfortable with them and are typical of these type of units.

A really quick calculation indicates the shell thickness should be close to 3.75"

If this gentleman needs anything else please let me know...

END QUOTE

Also, we utilize Ultra Narrow Gap Welding over traditional bevels, which greatly reduces the HAZ, amount of consumables, and obviously improves welding time. And we utilize advanced UT tecniques such as TOFD (Time Of Flight Diffraction per ASME Code Case no. 2235 Approval date 23/12/96), and C-B Scan and Phased Array tecniques.

Please don't hesitate to contact me if you need additional information.

 

[vesselfab]

We would use hot rolled plate for this reactor as a matter of course.

Forged rings are really long lead time items

what part if the world are you in

I may be able to point you in the right direction for a good delivery. Not all the shops are completey filled up.

If we were to be able to build this, we would be looking at late 2010 or early 2011. We're pretty busy, but some aren't

 

[jte]

Yet another ongoing concern would be to assure that the material can be welded... There have been presentations at recent ASME B&PV Code Comm and NACE meetings about very substantial delayed cracking issues which have caused difficulties for some reactor fabricators. They could weld 'em last year without problems, but not this year. A difficult issue to chase down. Not all fabricators have had this issue. If I recall correctly, the reported cases seemed to focus on Europe, while it was noted that Japanese fabricators seemed to not be experiencing the same issue.

jt

 

[stanweld]

The Japanese have been welding forged ring hydrocracker reactors and other heavy wall vessels for over three decades without undue problems. The principal problems seen in the past with the forged can bodies involved a greater tendency for disbonding of the weld overlay cladding than seen on the plate fabricated vessels. Whether this was related to the overlay methods used or differences in the surface condition of the machined forgings and the as-rolled plate was open to conjecture in the past.

Reheat cracking and delayed cracking is a greater potential with the Vanadium treated steel. Since the Japanese pioneered the use of the Vanadium treated CR-MO steel for heavy wall vessel construction over thirty years ago, I would assume that they had pretty much resolved that issue.

 

[ProcessSales]

As has been pointed out, a main issue is getting the head, plates and major forgings or order asap which can take every bit of 8 to 9 months. We have all the materials for a reactor on hand from a cancelled order, but unfortunately it's 1.25 Cr-Mo, not 2.25. We see many clients booking the long lead items in advance or awarding the EPC contract for just this reason.

With regard to weldability, we are aware of some problems that other fabricators have experienced, particularly with VE material, but to our understanding, this was primarily due to the consumables and not the plate and in one case lack of experience with the material. We order plates with very stringent purchase specifications and testing requirements and from very reputable mills: Dillinger, Voest Alpine or Industeel.

The frist 2 1/4Cr-1Mo-V Reactors were made in 1995 by Nuovo Pibnone. JSW made their first ones in 1998. And I believe Kobe also made their first ones in 1998. The material was approved by ASME Code Case 2098-1 in 1991. The Japanese have been working with Chrome Moly materials for 30 years, but 2.25 VE, though approved 1991, was not used much. It has become popular of late primarily because it reduces the weight, which is a major consideration for extremely heavy reactors. The size of equipment today can be enormous, so to be able to trim 10-15% of the weight can be a big advantage when you're talking about 1500 ton reactors. Of course there are other characteristics of the material, but this is the main reason it's being used.

For a reactor of this size, there really is no need for VE. It's a material that presents very unique challenges, and for sure there are only a handful of fabricators worldwide that can reliably work with it. We see VE typically on very, very large reactors ober 800 tons. Please also take potential future field repairs into consideration. It's hard enough to work 2.25 Cr-Mo in the field, much less VE.

Another consideration for your reactor should be the PWHT. If possible, try to ensure that your fabricator has a furnace large enough to do the stress relieving in one shot. Many do them in halves with a closing seam that's locally PWHT, so effectively at the seam, you've used two cycles.

Please advise if we can be of help.

 

[ProcessSales]

Hi SteveBP
Just wanted to follow up and see if you'd gone out for bids.