Normalizing a complete vessel ?

[Bangrod]

Our company designs and manufactures relatively small ASME VIII vessels. We currently have a project for a 36" OD vessel that was designed for the main shell section to be made from 1/2" thick SA-516 Gr. 70 normalized material so that we could achieve an MDMT of -49 F. The material was ordered incorrectly and was not normalized. This was not caught until the vessel was completely welded, pressure tested etc. including heads, 8 flanged nozzles from 1" NPS up to 8" NPS.

We have identified the following options that I would appreciate any feedback / input to the questions below.

1) Locate a piece of the plate material from the same heat number and have it impact tested at -49 F
Q: What are the odds of 1/2" thick non-normalized material passing at -49 F???

2) Normalize the entire vessel.
Q: Is this acceptable and what type of distortion should be expected at the shell, heads, nozzles?

3) Rework the vessel with a shell section made from normalized material, or just start over new with the correct material.

Thanks for your input.

 

[eliebl]

I am not sure about the flanges but it is unlikely that the SA-516 and SA-106 (nozzle necks) would be successfully impact tested at -49F.

What about the weld metal?

EJL

 

[metengr]

Bangrod;
Obviously, this is a nonconformance related to fabrication. The current plate material that was not supplied in a normalized condition will probably not meet impact requirements for -49 deg F (review Figure UCS-66, and impact exemption curves. Comparing not normalized versus normalized material is a large spread, Curve B versus Curve D, respectively) .

The risk of attempting to re-normalize a completely finished vessel is very significant. Namely, shell distortion concerns. As mentioned above, if the shell material was incorrectly ordered, what about the weld metal? If I was the customer, I would tell you to start over.

 

[gr2vessels]

bangrod,
Is not unusual to do the PWHT and normalization at the same time, but that is no guarantee that the impact test results will be improved to the desired level. Some distorsions are unavoidable, but a correct support during the heat treatment can minimise the impact of heat.

The ASME SA 20 refered to in ASME SA 516, specifies the V-notch test requirements as follows:

"12.1.1.1 Plates Ordered Without the Heat Treatment
Specified by the Material Specification — When
the material specification requires heat treatment but
the plates are ordered without such heat treatment, and
when Charpy V-notch tests are specified, one coupon
shall be taken from each plate-as-rolled. The coupon
shall be heat treated in accordance with the material
specification and the purchase order and the plate
qualified by specimens taken from the heat-treated
coupon."

Also, check your WPS / PQR for impact test requirements, for the vessel to be normalised after welding the entire vessel.

I would start, however, with impact testing the plate at -49F, to evaluate what you've got in hand.
Cheers,
gr2vessels

 

[metengr]

gr2vessels;
One thing, PWHT and normalization are not the same. Heating material to 1550-1600 deg F, and avoiding distortion is not the same as heating to subcritical temperatures (1100 deg F). This is also a finished vessel.

 

[gr2vessels]

I have had no intention of identifying the PWHT as normalisation of the entire vessel. I regret if it seemed that way. However, I still believe that is not unusual to normalise the entire vessel, after completing the fabrication, in order to achieve the impact test requirements and other properties. Is that correct or not?
gr2vessels

 

[metengr]

What it comes down to is risk, and final acceptance by the customer (and the AI). As a customer purchasing this vessel, if they can normalize w/o distortion and can show impact qualification, coupled with a surface NDT (my requirement), I would consider accepting the vessel.

There are significant risk hoops to jump through on this one, however.

 

[gr2vessels]

Correct, the risks are major and the expected results can only be estimated on some samples, heat treated prior to baking the vessels. If new vessels can be fabricated correctly and the ones made of incorrect material can be recycled for another use, the best option.
I am definitely unable to estimate the poster's actual risks, I am, perhaps, even underestimating the feasibility of the supporting structure during the normalising of the vessel. However, technically is possible to salvage the vessels and it is an alternative to late delivery or liquidated damages.
Good luck bangrod,
gr2vessels

 

[Bangrod]

Thanks to everyone for your input on this topic. The weld procedure that was used has been tested to -65 F. With the material not being normalized (curve B), we can only achieve an MDMT of -36 F using UCS-66(b). If it were normalized (curve D) then we could go down to -55 F.

We are going to have to further access the impact to cost and schedule to rebuild this vessel, versus the risk of normizing the existing vessel (assuming the customer and our AI will accept) and risk of distortion issues.

Thanks for your insights and please advise if you have any other suggestions or words of caution.

Thanks you.
bangrod

 

[stanweld]

Bangrod:
The WPS must be qualified with normalizing as the PWHT if you intend to normalize the vessel. Please understand that you are unlikely to meet tensile properties in E7018 type deposited weld metal after normalizing due to the low carbon equivalent.

Whereas the involved SA-516 plate was not purchased with
impact toughness testing, normalizing may not achieve the desired impact toughness at your test temperature. I've recently performed some impact tests on similar plate and the Code absorbed energy could only be met in the HAZ at 0 F. It is highly unlikely that normalizing such plate would provide Code absobed energy at -55 F.

 

[chaulklate]

If you do the PWHT, can you take the 30 degree F MDMT reduction as per UCS-68(c)?

 

[eliebl]

What are the other materials?

If the nozzles and flanges are also curve B materials then you may have your answer. 1/2" Curve B gives -7F. Lower that by 30F for the PWHT (Per UCS-68(c)), provided it is NOT a service requirement, and then show a stress ratio of about .82 then you would have the temperature you need. This relies upon the materials NOT being curve C or D. If they are curve C or D then the impact testing of the weld material or classified consumables would be required per UCS-67(a)(2).

If this is to be located in ALBERTA it would be a good idea to talk with your Design Surveyor at ABSA.

EJL

 

[Bangrod]

The other materials are -
Heads, SA-516 Gr. 70 hot formed at the normalized temperature above 1650F, curve D, MDMT = -55 F
Nozzle pipe, SA-106 Gr. B, curve B, MDMT = -155 F per UCS-66(b)
Nozzle flanges, SA-105, curve B, MDMT = -90 F per UCS-66(b)(1)(b)

The shell material that is not currently normalized is the only material that does not meet our -49 F MDMT requirement.

bangrod

 

[eliebl]

Bangrod,

As stated above the MDMT for the shell plate would be -36F using UCS-66(b). If you add UCS-68(c) (PWHT) does that get the -49F MDMT that you need? If that is the case then the only concern would be the weld metal as one of the materials is from Curve D. This would require that the consumables meet UCS-67(a)(2).

EJL

 

[Bangrod]

Thanks to everyone for your good input.

If we PWHT we can achieve the -49 F MDMT, but we then looked at UCS-67(a)(2) as EJL noted. Unfortunately, the WPS that was used has been impact tested to -65 F, however is not set up for PWHT. We have another nearly identical procedure that has PWHT and impact tested to -65 F. Both WPS use a filler metal of AWS ER70S-2 and ER70S-7.

We expect it is going to be difficult to get our customer to agree to the PWHT and use of UCS-67(a)(2) even though it might be allowed by our AI after review of the two WPS.

bangrod