Hard Stamping of Vessel Steel Plate 1

[VeryPicky]

Hi Guys,

We have a couple of vessels manufactured. One of the requirements is low stress stamping of the plates. All the welds are ground flush because of cyclic service and it does not make sense to have those solid stamps punched in the plate surface while we remove all the traces of undercut. The fabricator does not want to remove the stamping since they reckon hardstamping used by them and mill is low stress. Can you provide some guidance as what should be considered low stress stamping? In my opinion only round dot matrix stamping meets those requirements for our service.
Any papers or standards addressing that issue?
Thanks


Putting Human Factor Back in Engineering

 

[Goahead]

Manufacturers of round-face character stamps declare that they provide low stress marking.
Unless the requirement is quantified it would be difficult to verify the assertion.

http://www.welding-advisers.com/

 

[VeryPicky]

Good point Goahead.
I am not able to provide this definition and that is why I am searching and asking those questions to my esteemed colleagues.

Putting Human Factor Back in Engineering

 

[metengr]

We have used low stress stamps in the past on some of our pressure retaining items. These items are for Electrical Power Generation, steam service, which is not lethal service conditions. Today, we require the round dot matrix in our Technical Specification for purchasing pressure retaining items. Did you specify this up front in your Technical Specification???

Never had a problem with any of our pressure retaining items that were low stress stamped from years ago - welder symbols and ASME Code stamps. The stamped locations are not typically located in high stress areas of the component. Perhaps instead of trying to find papers on this issue, experience among users might provide your answer.

 

[VeryPicky]

Well, we specified low stress stamps in initial spec and that is now subject of a dispute. (What a low stress stamp is, actually? - nobody seems to exactly know)
New spec clearly defines rounded dot matrix.
And yes, the area I am talking about is a high stress area subject to thermal cyclic stress.

I was directed to ASME Section III Division 1, para NA-3766.6, subparagraph (b) 2.

I read the book and did not find the parqagraph quoted. Many stamp suppliers/manufacturers quote compliance of their product that paragraph without even assuring it is still there.

Do you have any publications, papers on this subject?

Putting Human Factor Back in Engineering

 

[metengr]

The information below is an excerpt from a Structural Steel Specification issued by the State of Florida. Might be of use regarding the definition of a low stress stamp.

http://www.dot.state.fl.us/specificationsoffice/Archives/Jan2002WB/D4600271.pdf

"There are two types of low stress dies; blunt-nose continuous or blunt-nosed interrupted dot die stamps (ie dies that are manufactured to produce impressions that are rounded at the base of the impression)."

What I found most interesting is the allowed depth limit of the impression is 1/32". Minimum face radii as a function of character size are also provided.

 

[VeryPicky]

metengr thanks.

What worries me is that my fabricators did not bother to investigate the issue to the same depth.
BTW: stamp depth was the reason why I started my quest on hard stamping. Approximate depth was over 1mm (0.04"). I rejected the stamping based on engineering practice more than anything else.

Thanks again and Merry Christmas, Happy Hanukah and season geatings.

Putting Human Factor Back in Engineering