Hi
I am working on stress analysis for transportation lines and i m using ASME 31.4 .
While during stress analysis i found that my current system is having 95 % stresses of allowable when i used 31.4 and design factor 5.0.
When without making any changes in matrl, temp and etc i.e. keeping system as it is i found that system is passed with 80% of allowable stress while using asme 31.3
when i run system as it is while using asme 31.4 and without puting value of design factor then also system passed with minimum % of allowable .

My question is as per asme 31.3 & asme 31.4 , allowable stresses for asme 31.3 is less than asme 31.4, i.e.if i keep system as it is and i changed only from asme 31.3 to asme 31.4 then genearating stresses should be high but in my case its not showing.
Even when i m not mentioned design factoe in asme 31.4 then also allowable stress are same,(i.e. for with or without design factor) then why its showing different stress and forces values ?
Matrl. API 5L Gr B
Temp 212 Deg F
Press 150 psi
Allowable Stress for asme 31.4 with / without design factor
Expansion Stresses: 25200 psi
Operating Stresses: 31500 psi
Sustained Stresses: 18900 psi

Allowable Stress for asme 31.3
Expansion Stresses: 46954 psi
Operating Stresses: - psi
Sustained Stresses: 20000 psi

If you're talking about the [Fac] entry on the "Allowable Stress Dialog", valid entries here range from 0.0 to 1.0. Check the "Help Text" here for details.

You can't just change the piping code, you have to analyze according to your Project Specifications. Each Code has its own rules as to how allowable stresses, and actual stresses are computed. In B31.4 you have the issue of "restrained" and "un-restrained" pipe and there are different stress equations for each.

You're not comparing apples and apples.