Hi Experts,

In one of our project , client specification had given the below ambient (dry bulb ) temperature conditions:

Absolute Maximum is 34.0
Absolute Minimum is-45.0
Coldest day is -25.0
Coldest 5 days is -20.0
Average maximum of warmest day is 22.0

Can you please explain what ambient temperature to be used for stress analysis?

Thanks

I'm also interested in the opinion of my fellow stress engineers in this topic. In terms of expansion stress range, I think the selection of ambient temperature will not have effect since the Code requires to consider the maximum stress range (maximum to minimum) anyway. The one will be affected is the restraint loads (nozzle loads & support loads). In one of our project the specification states that for Cold lines consider the maximum ambient and for hot lines consider the minimum ambient. And my bad experience with this criteria is when we have one project where we just use the average ambient of 21 deg C in one of Chilled Water lines (temperature if I remember right is below 21 deg C) connected to pump in which we have written this criteria in the specification to use 21 deg C as ambient and was approved. Construction time when our manager calls us and someone commented to use maximum ambient for Cold lines (many arguments arise but in the end we have to do something to close the comment). But in my 23 years of experience most of the projects I've involved with considers just the average ranging from 20 deg C to 24 deg C. Just make sure that all stakeholders involved are in agreement with your basis to avoid any major changes in the end of project.

Just correct any wrong statement I've made.

Cheers!!

Anyway it's the pump nozzle load issue that we encounter by changing the ambient from 21 deg C to 33 deg. C. Just highlight this issue to your manager to avoid major change orders in the end.

Cheers!!

It seems this is a common problem among stress engineers. I faced this issue and used a max ambient temp to satisfy the client and struggled with pump nozzle qualification, and finally ended up adding more flexibility.
A more balanced approach is to use the average maximum for restraint loading and creates max-min temp cases separately for max range.

Thanks

Thanks Borzki & Naren for your response.

CAESAR II Experts, if this is a common problem among all stress engineer,can you pls through the path forward for my above case?

You can go for 22 deg. C ambient but make sure you write it in the stress specification reviewed and approved by the client.

Warm Regards,