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WCSRF (Weld Creep Stress Reduction Factor) & ASME VIII-1/VIII-2 5

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Ganfoss2

Ganfoss2

Mechanical
Oct 23, 2007
32
Does someone have some news if a WCSRF is applicable to design a component of a pressure vessel in creep range temperature with ASME Sect. VIII Div. 1 or Div. 2?

OR

If a value of WCSRF has been already "implemented" in the definition of the ALLOWABLE STRESS (creep range) of ASME Sect. II Part D in addition to the Safety Fators applied on the average stress to produce a creep rate of 0.01% @ 1000 hr or on the average/min stress to cause rupture at the end of 100000 hr?

OR

If there is a INTERNET DATABASE of "Welding Consumables" that outline such value of WCSRF?

----

Ex.: Typical Materials: 1.1/4Cr-1/2Mo-Si (ASME Grade 11); 1Cr-1/2Mo (ASME Grade 12) and 2.1/4Cr-1Mo (ASME Grade 22).

I have looked more in deep inside the ASME VIII-1 and VIII-2 Code, but there aren't any specific GUIDELINES or MINIMUM REQUIREMENT or DISCLAIMs on the "creep design" (only the definition of the allowable stress: not more, not less!).

NOTE: In case of EN-13445 Design there are more details regarding the "Creep Design" (From ISSUE No. 27 only! Chapet 19!).

Somebody know a particular reason why ASME do not take in account such coefficient in the CREEP DESIGN?

ASME is still "incomplete" for a creep design?

Further more it is REALLY IMPOSSIBLE to get the origional data by which it is possible to calculate the allowable stress stated in ASME II-D (while with a "EN Material Specification" - Ex. 10028 - there are the main basic data to allow this operation. In ASME/ASTM Material Specification no in ASEm II-D ... NOTHING!). This would be very useful in case of EN-13445 DEsign with ASME/ASTM Material!

Thanks in advance.

ANN

NOTE: Further more in case of external pressure, conical transitions, large opening, tubesheet design where the yield stress can play a significant role in the design of the component, there are NO DATA nor ROULES to apply in ASME!
 
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The allowable stresses in Section VIII, Division 1 include for the effects of creep. Division 2, on the other hand, specifically excludes designing in the creep regime (Code Case 2605 notwithstanding). The rationale for excluding creep design in Division 2 is that there are additional failure mechanisms that are present in designing for creep that the particular rules (especially in the Design By Analysis portion) do not account for.

BTW - the method for arriving at the creep-governed stresses are provided in Section II, Part D.
 
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Do you know any SOURCE (BOOK/TECHNICAL-PAPERS/WWW) regarding:

a) the average stress to produce a creep rate of 0.01% @ 1000 hr.

b) the average and min stress to cause rupture at the end of 100000 hr.

for ASME/ASTM MATERIALS ONLY, like: 1.1/4Cr-1/2Mo-Si (ASME Grade 11), 1Cr-1/2Mo (ASME Grade 12) and 2.1/4Cr-1Mo (ASME Grade 22), Plate/Forgings/Pipe/Tubes ?

Thanks in advance.

----------

In addition: do you know any Companies that Supply WELD CONSUMABLE for such materials (Ex.: ESAB, Boehler, ...) that has in its CATALOGUEs the result of TESTS as prescribed in EN 13445-2:2002 (E) Issue >= 27 (Ed. 2007-06) "Annex C" (Procedure for determination of the weld creep strength reduction factor = WCSRF)?
 
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Ganfoss-

You might find ASME III-NH and III App T interesting. One source I would suggest you try to find is a 1970 book/pamphlet put out by the ASTM titled An Evaluation of the Elevated Temperature Tensile and Creep-Rupture Properties of Wrought Carbon Steel, ASTM Data Series DS 11S1. It cost me $6 a few years ago - I remember that it wasn't in the ASTM's catalog, but a bit of persistence on a phone call convinced the lady to check some non-computerized list (or their bookshelf) and she mentioned that there were only a few left. I imagine they aren't planning to reprint 'em. There was a similar publication, DS 47, which I think they were out of stock on. That's the one which dealt with the low alloys.

jt
 
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The ASME B&PV Code, 2008 addendum for Section I will have published weld strength reduction factors for the first time. The table of weld strength reduction factors supports PG-26, and is in Table PG-26.

The weld strength reduction factors were developed based on a joint effort between ASME B31.1 and ASME Sections I and II, input from various technical sources, and actual creep rupture test data.
 
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There are a few of the ASTM Data Series that found several years ago: The DS 11S1 is for carbon steels; DS 50 is for low alloy (Cr-Mo), DS 6S2 for 2-1/4 Cr, 1 Mo, and DS 5 S2 for austenetic CRES (304, 316, 321, & 347).
 
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TGS4: said:
Division 2, on the other hand, specifically excludes designing in the creep regime (Code Case 2605 not withstanding)
Click to expand...
Sorry, my latest supplement (7) of BVPC only arrives to 2604.
I'm doing a comparison between Div2 and EN13445 as per creep design is concerned. I'll ask our supplier if new supplements are available, but in the meanwhile I wonder if you could summarize the 2605 topics.

Thanks

Ishmael
 
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Dear All,

This is may conclusion on thsi issue:

"For Section I and Section VIII, Div 1 (VIII-1) applications, the allowable stress criteria are given in Appendix 1 of Part D. The allowable stress at elevated temperature is the lesser of:

(1) the allowable stress given by the criteria based on yield and ultimate strength,

(2) 67% of the average stress to cause rupture in 100,000 hours,

(3) 80% of the minimum stress to cause rupture in 100,000 hours

(4) 100% of the stress to cause a minimum creep rate of 0.01%/1000 hours.

NOTE: Above 1500°F (815°C) , however, the factor on average stress to rupture is adjusted to provide the same time margin on stress to rupture as existed at 1500°F (815°C).

Unlike previous editions, the 2007 edition of Section VIII, Div 2 (VIII-2), covers temperatures in the creep regime. The time dependent allowable stress criteria for VIII-2 are the same as for VIII-1. However, because the time independent criteria are less conservative, tensile strength divide by a factor of 2.4 versus 3.5, the temperature at which the allowable stress is governed by time dependent properties is lower in VIII-2 than VIII-1

The EN 13445 allowable stresses are time dependent, analogous to what is done in Subsection NH. They are also a function of whether there is in-service monitoring of compliance with design conditions. Provisions are also made for weld strength reduction factors, analogous to Subsection NH.

The basic allowable stress parameters in EN 13445 in the creep range are the mean creep rupture strength in time, (See Point 2 of ASME above criteria), and the mean stress to cause a creep strain of 1% in time, T. For DBF rules, the safety factor applied to the mean creep rupture stress is 1/1.5 = 0.67 = 67% if there is no in-service monitoring, and 1/1.25 = 0.80 = 80% if there is. There is no safety factor on the 1% strain criteria. If there is in-service monitoring then the strain limit does not apply, but strain monitoring is required.

Thus, for a design life of 100,000 hours in the EN code without in-service monitoring, the base metal design allowable stress will be the same as in VIII-1 when the allowable stresses are governed by creep rupture strength (remembering that VIII-1 allowable stresses are based on 100,000-hour properties even though there is no specified design life in VIII-1).

weld strength reduction factor: Creep strengths in weld metal and heat affected zone differ from those in parent material. Hence a weld strength reduction factor (z.creep) shall be used. Generic data are required from creep tests performed on welded joints similar to the vessel governing welded joint. If, at design lifetime and design temperature, minimum strengths for creep rupture and 1% creep strain are not lower than the mean values for the parent material minus 20% or the minimum values (if available), then z.creep = 1,0 otherwise, zcreep = 0,8.

For 1 Cr and 1.1/1Cr Material, some WELD CONSUMABLE Manufacturers have stated in the WELD CONSUMABLE PRODUCT DATASHEET a z.creep factor equal to 0.80 (we have to change the BASE Material towards something close to 2.1/4 Cr material with the consequent change of the weld consumable material to get z.creep = 1.00).

So if NO TEST shall be performed to evaluate the weld strength reduction factor , but a IN SERVICE MONITORING of the Equipment shall be implemented, then

Allowable Stress EN 13445 = Mean Creep Rupture Strength / 1.25 x 0.80 = 0.64 = 64% that is very close to the value of allowable stress stated in ASME VIII-1 (safety factor = 67%).

Only a test to demonstrate a z.factor = 1.00 may lead to a EN-13445 Design Improvement respect to ASME VIII-1 or VIII-2 Design.

NOTE: in ASME I, ASME Nuclear NH and ANSI B31.1 the z.creep factor now start to be used in the Design Rules of these Codes. In ASME VIII-1 and ASME VIII-2 actual Issues, no z.creep factor are mentioned! Perhaps in the future releases, their factor hall be present! "

Have yoy any comment? Let meknow (if any).

Sincerely,

ANN
 
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Sorry, I have forgot one this (most important):

"Comparision with ASME VIII-1/VIII-2 DESIGN CODE with the ASME/ASTM Material Standard (allowables stored in Part. II-D) vs. EN-13445 DESIGN CODE with the EN Material Standard (Allowables in EN Mat. Standard)".

If I perform a mix .... the above statement doesn't work anymore.

NOTE: REALLY IMPOSSIBLE to get the origional data by which it is possible to calculate the allowable stress stated in ASME II-D in case of CREEP!

ANN
 
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