Different grade materials

fatigue · **Joined:** Fri Dec 01, 2006 12:37 pm **Posts:** 3

We propose to use combination of SA-516 Gr. 70 and SA-516 Gr. 60 materials together on a pressure vessel due to availability problems in the market.

Is there any restrictions for using of different grade materials (such as, heads are SA-516 Gr. 70 and shells are SA-516 Gr . 60 etc.) in a pressure vessel according to ASME Section VIII Div. 1?

Gonzaga · **Joined:** Sat Dec 15, 2001 1:00 am **Posts:** 610

No restrictions. Of course apply the apropriate allowable stress from Sect II/D. It is not permitted to take the advantage of the higher stress in metal available for compensation to compensate openings in shell of the lower grade.

fatigue · **Joined:** Fri Dec 01, 2006 12:37 pm **Posts:** 3

Thank you Gongaza for your reply.

Is there any interpretations or case for this query?

Frohnert · **Posted:** Sat Dec 02, 2006 11:26 am

fatigue:

You do not need an interpretation or case, just have a look into the code at UG-18:

Code:

UG-18 MATERIALS IN COMBINATION
Except as specifically prohibited by other rules of this Division, a vessel may be designed and constructed of any combination of materials permitted in Subsection C, provided the applicable rules are followed and the requirements in Section IX for welding dissimilar metals are met. ...

Additionally Gonzaga wants you to keep the requirements of UG-41 (a) in mind:

Code:

UG-41 STRENGTH OF REINFORCEMENT
(a) Material used for reinforcement shall have an allowable stress value equal to or greater than that of the material in the vessel wall, except that when such material is not available, lower strength material may be used, provided the area of reinforcement is increased in inverse proportion to the ratio of the allowable stress values....

... No credit may be taken for the additional strength of any reinforcement having a higher allowable stress value than that of the vessel wall. ...

As you can see it´s neither "unusual" nor "prohibited" what you intend to do in this matter.

Michael

brown · **Joined:** Tue Jan 16, 2007 8:57 am **Posts:** 1

it is recommended to use same material for the reinforcement pad which is directly welded to vessel wall, beside UG-41(a), any other basis to support this idea?

Gonzaga · **Joined:** Sat Dec 15, 2001 1:00 am **Posts:** 610

brown wrote:

it is recommended to use same material for the reinforcement pad which is directly welded to vessel wall, beside UG-41(a), any other basis to support this idea?

Not in the Code. However it is good practice to have homogeneous material and have advantage in using same qualified WPS as used for the shell fabrication. Mauro

akaujalgikar · **Posted:** Sat Mar 31, 2007 3:50 pm

think about impact test values SA516 Gr. 60 has heigher impact strength thank SA516 Gr. 70.

Regards,

anant.

Gonzaga · **Joined:** Sat Dec 15, 2001 1:00 am **Posts:** 610

akaujalgikar wrote:

think about impact test values SA516 Gr. 60 has heigher impact strength thank SA516 Gr. 70.

Regards,

anant.

How can you make such a statement?
Anyway: there is no better or worst material. Use of material depends on design, economical and many other considerations. ASME makes the rules, the designer makes his choice within the rules. Mauro.

Different grade materials

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