Max. Allowable stress in B31.1

[rocio74]

Hi all,

In ASME B31.1 ed. 2004, the SE to be used in the wall thickness calculation formula (para. 104.1.2) has to be taken from Appendix A.

The value given in the Appendix provides "Maximum Allowable Stress Values in tension" and E/F (joint efficiency/cast factor) in separate columns.

In mentioned para. it is said "The value of SE or SF shall not exceed that given in Appendix A, for the respective material and design temperature. These values include the weld joint efficiency E, or the casting factor F".

The question is: for calculating the wall thickness, is it required to multiply the value E given in the table by the maximum allowable stress or not? I mean, S·E or SE?

It seems that the value given in the table already includes this factor as per the mentioned para.

Any help would be highly appreciated.

Thank you all
Rocío

 

[NozzleTwister]

Yes, the values in Appendix A of B31.1-2004 already include the joint efficiency factor.

NozzleTwister
Houston, Texas

 

[ColonelSanders83]

The allowable stress values given in table A-1 already have the appropriate weld joint efficiency factor taken into account.

You can check this by comparing the allowable stress value for A53 Grade B Seamless pipe with the allowable stress value of A53 Grade B ERW pipe.

A53 Gr. B Seamless E=1, S=15,000 psi
A53 Gr. B ERW E=0.85, S=12,800 psi

 

[rocio74]

Thank you very much for your help,

On the other hand, in ASME B31.3 ed.2004, I understand for calculating the wall thickness it is required to multiply the value E/F given in the table by the maximum allowable stress, I mean in this case we have S·E, is it like that?


Thanks in advance,

Rocio

 

[ColonelSanders83]

You are correct. Note 1 for appendix A states quite clearly that B31.3 requires modification of the allowable stress by the appropriate factore listed in table A-1B.