Does shell thickness vary in ASME Sect VIII Div. 1 U-stamped Vessel ? 1

[ak1965]

We are getting a process column designed. Our designer says that if opt for ASME U-stamp, the thickness of shell would increase & design calculations to be done again.

My Query:

1. Do all vessels, being designed & fabricated as per ASME Sect. VIII Div.1, need U-stamp ?

2. If yes, Does it cause a variation in Design calcualtions?

3. I believe that U-stamping governs the inspection clauses to be followed as per UG 91 to UG 97 of ASME Sect. VIII Div. 1 and do not affect the design calculations.

Forum may please opine ...!

 

[gr2vessels]

1. No. However, it depends on where is installed, insurance requirements, Client specification.
2. No, it does not cause any variation.
3. U-stamp confirms adherence to ASME code. It does not affect the design calculations.
Please note that the above applies in all developed countries who value safety of their own and others. Unfortunately, the world is full with shonky manufacturers prepared to take any necessary shortcuts to make it cheaper the manufacture, at the expense of safety of others. Don't buy anything made in China and sold 'guaranteed' to conform to ASME. I stopped trusting even Lloyds China, when the same person signed the test operator, the QA manager and the Lloyds certifying representative.
Cheers,
gr2vessels

 

[ak1965]

Thanks gr2vessels

 

[jtseng123]

ak1965,
The fear factor hitting to the roof is someone working for you who pretends to know everything, and gives you wrong information that leads you to make wrong decision or judgement. This is due to their lack of knowledge and experience. Ask your designer why he 'thinks' U-stamp will increase the thickness ? Ask him to prove it or where it is in the code. I have people working for me and when I see something weird, I ask what is their basis to prove their point.
"you think, I think" in pressure vessel battle field most of the time won't hold water. Anything has solid basis behind. It is just tremendious info there that no one knows all.

gr2vessels, you got lemon car. Sorry to hear you poor experience. We purchase vessels around the world. Malaysia could be worse than China. China has many good shops. Don't deny all.

 

[gr2vessels]

I am not pretending anything;- I only know that the vessel thickness does not depend on the application of U-stamp. I can state this without fear or intent to frighten anyone. Can you jtseng123 share with us the basis of your assessment on my experience and knowledge?
Best regards,
gr2vessels

 

[JStephen]

The way the original question is phrased, it could be taken to mean that if you change the design code (to ASME as opposed to other codes), the thickness would change.

 

[rmw]

If your builder states that stamping the vessel will result in increased thickness, it means that he either hadn't done the design calculations or wasn't going to build it to what the calculations dictated.

Something is fishy here.

What did your specification call for?

rmw

 

[ak1965]

Good & healthy Debate... thanks to all... I am unquoting, what our designer mentioned us when we asked them to design our vessel with U-stamp.

Guys... my concenr would be more clear now...!
--------------------------------------------------------------------------------------------------------------
"UNQUOTE"
Dear ....

As per the trailing mail, both equipment are under the ‘U’ stamp. This will affect the following.

1.Due to the ASME documentation & various inspection stages,the delivery period may get extended by 3-4 months.
2.The cost of the equipment also may increase by 30 to 35%.
3.The thickness of the Vessel may increase due to various design factors & loads as per ASME Section.

So, we need to revise the whole design including equipment General drawing & enquiry specs. accordingly.
---------------------------------------------------------------------------------------------------------------

How much justified their statement is?

 

[jtseng123]

ak1965, that quote is purely BS. I bought hundreds of pressure vessels for more than 20 years, from vendors around the world, either U or no U stamp (many overseas projects, customers do not require U stamp) ,no difference in cost, no difference in thickness, no difference in delivery schedule, and no difference in all design dwgs except the dwg for the nameplate will have U symbol and NBR. As long as your spec is asking for "design, fabrication and inspection to ASME code", regardless U stamp or not, the documentationis are 99.99% the same. At one time we were charged by a Korean vendor for $100 per vessel to apply code stamp and National Borad Registration, peanut.
ak1965, you are getting a lemon supplier. You will need to fight for it.

grevessels, your original reply regarding the design is 100% correct. I have nothing to against you. You misread what I wrote. I told ak1965 that his "designer" is lack of knowledge and experience, giving him wrong info (thk will increase, etc). I want ak1965 to ask his "designer" to prove it.

 

[jamesl]

Of course there will be additional cost for stamping a vessel. If the vessel is stamped, the shop has to have an AI on the vessel. AI will make several trips to shop reviewing documents, do some inspection work, review the forms and stamp. It will cost two or three thousands of dollars in the US for an average vessel.

 

[ak1965]

Thanx all .... froum coming to a uniiform conclusion...!

We have strongly asked our designer to clarify their version on the effects stated by them with U-stamp.

Lets wait what he replies.. i will share here...!

 

[REGRUMBLE]

The identical vessel with a "U" stamp will cost a small amount more but not two or three thousand more. Our AI generally makes 3 visits for the average vessel @ $150 each and a small amount of paperwork to register it with NB or CRN but in total it would be only $1000. But back to the original question it would not change calculations or design.

 

[racookpe1978]

Sounds to me like the business writing the quote above is trying to pay for HIS qualification and HIS time to get HIS shop approved for U stamping the vessels HE wants to make. A shop already making vessels properly and under code will not need "months" of extra time.

 

[jamesl]

Regrumble,

Sounds like you made a good deal with your AI. $450 total per vessel is really good price.

I thought AI is aupposed to come in take a look at some MTRs, drawings, review some RT films, witness hydrotest, review U-1 form and sign off. For a simple vessel, three visits may be enough. However I used to see AI bill four hours minimum per visit including driving time to and from the shop. That was many years ago.

On the other hand, if it costs shop $1000 for stamping, do you typically quote for the Buyer $1000 only? Just curious.

 

[REGRUMBLE]

If our cost was $1000 we would mark it up but at the same time we often build 2 or 3 vessels so that we can divide the cost. Our AI typically makes one visit for MTR's and drawings (initial) one visit for RT and Hydro and the last for paperwork. Often another visit for fit up if required on large vessels but if you have your paperwork ready he can also sign it as soon as the hydo is done so over the cost of our vessels the actual "U" stamp process does not amount to much. We build fairly large vessels so the total does not seem significant. I guess if you are making a small tank the cost is large by comparison.

 

[XL83NL]

In view of this thread, not meaning to hi-jack it; does the AI has to stamp the nameplate for a U-stamp vessel?

Or let me re-phrase my real question; when a vessel (for some reason) needs a new nameplate (e.g. the one already in place was of the wrong format), does the AI has to stamp every now to be attached nameplate? Or does the AI even not has to visit the shop when the nameplate is attached in the first place?

 

[ak1965]

Original Queries was whether all ASME Sect VIII designed vessels need U stamp & do the shell thickness vary on higher side if we opt for U stamping?

gr2vessels replied it well in the very 2nd post however later the post got diverted more towards to AI cost, which was informative as well.

The debate was a quality debate and gave us a nice conclusion well in-line to our thoughts about the issue.


Off-late, our designer also modified their original version & accepted that ASME U-stamp would not affect the delivery period & cost, if the vendor is ASME approved vendor.

 

[JakeR82]

No,

If the vessel is designed to VIII there is no difference at all in the calculations/thickness between building it and building it code stamped (U-Stamped). The difference comes from the inspection/quality procedures to be done to the vessel and the items the Authrozied Inspector needs to look at.

Our company typically charges about $1500 more for a code stamp vessel, depending on the complexity and the information the AI needs to look over.

XL83NL, I believe you need to have an R stamp to do that, but I'm not positive. I know you can't touch any part of the vessel that is pressure containing after the AI has initially signed off on it. Therefore, if the nameplate is directly attached to the shell, you can not touch it, unless the plate itself is on a bracket. If the bracket is welded I think you may be able to replace the nameplate provided you inform the National Board.

 

[XL83NL]

@ JakerR82; the vessel under discussion is still in the workshop where it was constructed, so it hasnt been installed yet, not even been commissioned. Second, the NPL is not directly attached to a pressure containing part, there's a bracket in between. I'm not sure if the vessel is registered at the National Board as the vessel is shipped (later on, when its part of a complete plant) from EU to South-Africa.

 

[JakeR82]

@ XL83NL: I could ask our AI if you want. She would help clarify what could be done.