Stress Analysis 2

[GoHawkbeaks]

Hello all,
First post here so I figured I'd start out with an easy one:

I was looking for some insight on a assessment I have been working on. In an effort to improve the efficiency of the plant, I have been tasked with investigating whether or not it is possible to increase the design temperature of a high pressure steam piping system running from existing HRSGs to existing steam turbines.

We were provided with the pertinent information such as current design pressure, temperature, original piping spec, pipe material grade and pipe wall thickness data to calculate hoop stress per ASME B31.1. Using the minimum pipe wall thickness that we received, I calculated that the current design conditions for the pipe (725 °F, 960 psig) result in a hoop/maximum allowable stress ratio of nearly 1.

My question is:
Would further investigation or a full stress analysis of the piping system to determine actual combined stresses prove to be worthwhile? Or is knowing that the current hoop stress on the pipe is equal to the maximum allowable stress value dictated in ASME B31.1 enough to determine that there is no opportunity for an increase in design temperature?

Any insight would be much appreciated. Thank you.

 

[SNORGY]

GoHawkbeaks,

If I was in your situation, I would say we are done without looking into it much further. You could do a simplified stress model for a representative portion of the piping to prove it, but in my opinion, you know what the answer is likely to be already.

 

[B.L.Smith]

Dear GoHawkbeaks,

In your stress analysis spec is a table that determined which lines(according to temperature vs pipe size) should analyze.
Also in most cases, hoop stress is for determining wall thickness. Many pipe path may not have problem with internal pressure but thermal and weight cause over-stressing in some points. Thus, study your stress analysis spec for lines that you have doubt.