I would like to share some points below:-
What about below –425F(-254 Deg.C)?
According to paragraph 323.2.2 (c) we may use austenitic stainless steels below –425F(-254 Deg.C) if we follow the requirements of Table 323.2.2 Column B cell B-4. Unfortunately the requirement of cell B-4 (after the reading of several notes and other paragraphs) requires us to impact test at the minimum design temperature. For liquid helium piping this would mean toughness tests performed at –452F(-269 Deg.C), essentially impossible.
However, the Code does give us some guidance on how to proceed. In Chapter I "Scope and Definitions" there are several paragraphs giving us direction. These paragraphs are included in Section 300 (b) "Responsibilities" and 300 (c) "Intent of the Code". A reading of these paragraphs, in our opinion, gives the owner, designer and manufacturer some latitude in this situation, where the Code doesn't prohibit the use of these materials but the testing requirements are not physically possible to perform. In these situations, we have recommended to the owner that good engineering practice would be to apply the requirements of a more restrictive Code, namely the ASME Boiler and Pressure Vessel Code Section VIII Division I to this situation. Part UHA "Requirements for Pressure Vessels Constructed of High Alloy Steel", specifically paragraph UHA-51, addresses Impact Tests (e.g. Toughness Tests). The rules for austenitic stainless steels in this situation are summarized below.
- For MDMT below –320F (-196C) impact tests are REQUIRED of all raw material, weld procedure qualifications for both the weld and heat affected zone for each type of weld process, and production weld test specimens (weld and heat affected zone) for each type of weld process.
- Impact tests may be Charpy Tests performed at –320F (–196C) only if Type 316L weld filler metal is used (and measured to have a Ferrite Number no greater than 5). THESE TESTS ARE PERFORMED AT –320F REGARDLESS OF THE ACTUAL LOWER DESIGN TEMPERATURE. Otherwise, testing using ASTM E 1820 JIC method at the minimum design metal temperature must be used.
- UHA-51(g) exempts the impact test requirements above due to low stress. Where vessels that have a coincident ratio of design stress in tension to allowable stress of less than 0.35, impact test of materials and weld procedures and production welds is NOT required.
Thanks & Regards
Amit Pahuja
Sr. Welding Engineer
B-Tech(Welding), IWE-IIW
CSWIP-3.1, NDT Level-II
BOIST-OFFSHORE,
The impact tests are not required when the shape/size/thickness of the
element does not allow machining a charpy specimen.
As max OD is 60.3mm and the thick2.77mm. These two combined size
constraint (thickness & radious of curvature) does not allow machining
the charpy specimen in the tube.
To perform impact test it shall be necessary to weld thicker material,
in this case welding energy will not be representative of weld .
Base material TP304L,welded with dedicated filler ER308L.by TIG
process.My experience this configration gives confident good weld
toughness garentees good result,no risk of embrittlement at cryogenic
temprature.
Amit Pahuja
Sr. Welding Engineer
B-Tech Welding, IWE/EWE-IIW,
cswip-3.1, NDT Level-II
On Oct 1, 6:48 pm, "pgoswami" <pgosw...@quickclic.net> wrote:
> Hi Amit,
>
> ASTM A-370,or ASME SA-370 allows impact test on subside specimens.If you
> look at Fig-12, A/SA-370 the smallest allowable thickness is 2.5 mm.Table-9
> provides the acceptance criteria for various sub size specimens.
>
> You client is right , minus(-) 269 deg C is the ultimate for any material.
> Although austenitic S.S is generally though to have sufficient DBTT values
> at this temperature, it's better to prove the same, during fabrication.
>
> B-31.3 concerns are generic, it specifies that impact is not required if the
> width at the notch is less than 2.5 mm.But the discussion of B-31.3 does not
> address such low MDMT as -269 Deg C.
>
> If you have the Mill supplied MTR TESTED AT -269 DEG c ? and the MTR of
> welding consumables impact tested @ -269 Deg C, then your client may have
> some backup document for acceptance.
>
> Thanks.
>
> Pradip Goswami,P.Eng.IWE
> Welding & Metallurgical Specialist & Consultant
> Ontario,Canada.
> Email-pgosw...@sympatico.ca,
> pgosw...@quickclic.net
>
>
>
> -----Original Message-----
> From: materials-welding@googlegroups.com [
>
> <mailto:materials-welding@googlegroups.com>
> mailto:materials-welding@googlegroups.com]
> Sent: Friday, September 30, 2011 1:05 PM
> To: Materials & Welding
> Subject: [MW:12590] CVN Impact test on 304L 2.77mm thick B31.3 piping
>
> Please I need your assistance:-
>
> I have Helium gas Pipeline 304L to be welded by ER308L ,having MDMT at -269
> Degree Centigrade , but the thickness of my Pipe is 2.77mm , Which is
> exempted from the impact requirements from B31.3 Chapter-III, Table323.2.2
> Column B, B-4, Notes -6, Impact test are not required when maximum
> obtainable charpy specimen has a width along the notch of less than 2.5mm.
> but my client is not ready to accept that condition/constraint of B31.3. he
> needs explanation that How the material thickness(2.5mm) will bear that MDMT
> at -269 Degree Centigrad., even Obtainable charpy specimen is not possible,
> but How to convince the client the material will have the properties at that
> temperature.
>
> Thanks & Regards
> Posting on behalf of: Amit Pahuja
>
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