Hi everyone,
Can we use Hot Modulus of Elasticity in branch stiffness calculation?
We are analysing a existing system which is in operation for last 30 years without any issue. But when we analyse it, it shows failure. Can we use Hot Modulus of Elasticity for branch and elbow flexibility calculation?

Theoretically yes!!

Stresses calculated using Hot Mod of Elasticity would be real time.And if the piping is working satisfactorily for three decades, you can go for this approach logically.

Thanks SJ for your prompt reply.
My concern is, As per B31.3 stress should be checked with Ec whereas loads can be calculated using EH.
In my case we are doing FEA analysis of component which is showing failure. For boundary condition we are taking loads from Caesar II model. If I use EC for load calculation, loads will be higher and FEA stresses will also be on higher side. If I use loads with Eh, loads will be lower and hence stresses will also be on lower side. Basically I am using advantage of Eh in my stress calculation, is this approach correct?
Similarly, when we calculate branch flexibility using FEA software such as FESIf, we use Ec but if we use Eh instead of Ec, branch stiffness will reduce and we will get more flexibility.

B31.3 clearly states that the reference modulus of elasticity (Young's modulus at ambient temperature) shall be used in the expansion stress range calculation. Markl did his STRAIN range work at ambient conditions, using Eh would artificially reduce the stress range for that strain range (stress=strain*E).

Dave,
I understand that B31.3 clearly states that Ec (cold elastic modulus) shall be used for expansion stress range calculation. My question is on using Hot Modulus of elasticity for branch stiffness calculation.
FESIF gives flexibility (stiffness) and SIF values for branches. One on the input is elastic modulus. If we use Cold Elastic modulus,it will result into stiffer branch connection. If we use hot modulus , branch connection will be more flexible.
The stiffness values calculated from FESIF (or any other FEA software) will be used in Caesar II calculation with Cold elastic modulus (Ec) for expansion range calculation. Is this correct approach?

If you wish to calculate an expansion stress range in accordance with B31.3, then you will not use a hot modulus of elasticity to set the stiffness of tees.