Cold-Stretching MDMT

[jgibbs22]

Hey Everyone:

I know that the 2013 Code recently adopted Cold-Stretching for ASS vessels, but I wanted to confirm the Code allowable limit to the MDMT. I thought the Code says -320 deg. F is the lowest it can be used at, but I was hoping someone could determine where that comes from? Do any of the European Codes allow using Cold-Stretched vessels to store liquid hydrogen?

 

[metengr]

Here is an excerpt from my ASME B&PV background code notes on cold stretching and other international codes;

It is known that austenitic stainless steel work hardens and thereby increases the yield strength when deformed plastically at room temperature. The increased yield strength results in higher allowable design stress for the rules where design stresses are controlled by design margins to yield strength only (i.e. no design margin applied to ultimate tensile strength). This concept has been used successfully for many years in the Swedish Pressure Vessel Code and has been recognized for several years in some of the European countries such as in Germany. In the recently developed European standard prEN 13458, similar rules have been incorporated. Additionally, in the new ISO cryogenic vessel standard being developed under ISO TC / 58/ 220 Committee, the same rules are being incorporated. These rules are similar to Swedish, ADM ,prEN 13458 and AS1210 Codes.

 

[jgibbs22]

Thanks for the response!

I have been trying to get my hands on the ISO or the European Code to try and dig into this folder. I believe the ASME Code limits you to -320 F, but I am hoping to go colder and maybe even design using Cold Stretching a Liquid Hydrogen vessel at low pressures. Problem I have is the Code only examines the vessel using normal Code design equations and then provides you with the stretch pressure and strain rate info to follow, along with the process. Has anyone seen any good papers on using cold stretched 304L for liquid hydrogen temps? Or fracture toughness studies on cold stretched ASS?

 

[metengr]

Look at the following;

http://www.absa.ca/IBIndex/ib13-008.pdf

file:///C:/Users/owner/Downloads/ASME_BPVC_Update_Website_Flyer.pdf

 

[metengr]

Mandatory Appendix 44 in the 2013 Edition of Section VIII, Div 1

MANDATORY APPENDIX 44
COLD STRETCHING OF AUSTENITIC STAINLESS STEEL PRESSURE
VESSELS



44-2 GENERAL REQUIREMENTS
(a) The use of this Mandatory Appendix is contingent
upon approval from the user or the user’s designated
agent.
(b) Vessel wall thickness shall not exceed 1.2 in.
(30 mm).
(c) Minimum design metal temperature (MDMT) shall
not be colder than −320°F (−196°C).

 

[jgibbs22]

Thank you for the directive link! Do you have any insight into why the Code limits the MDMT to -320??

 

[metengr]

Conservatism on cold formed austenitic stainless steels. My take is when you cold work, stored energy can result in altered corrosion and hydrogen embrittlement concerns.

 

[EdStainless]

One issue with 304 (and most 3xx alloys) is that they are metastable.
When you cold work you will get some martensite formation. This material is brittle, has a DBTT, and may be sensitive to hydrogen embrittlement.
I have seen cold formed vessels made from 219 used for LH service. But I have only ever seen small ones.

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P.E. Metallurgy, Plymouth Tube