Significance of downcomers and Risers-HSRG

[shumach]

How significant are the downcomer and riser stiffness? Can you also use the B31.1 piping spec, while the shell side is as per ASME Section 1? does anyone have any opinions on this ?

 

[saplanti]

The stiffness is required for the seismic , wind and dynamic applications. You need to check the stresses under the sustain, thermal and occasional loads. The stresses at drum and header connections and other locations may force you to make risers and downcomer flexible than you have thought.

These are the boiler integral piping and ASME Sect I (Fig PG.58.3.1 does not show these, however) has the full administrative juristiction and technical responsibility.
You may run the piping analysis by using ASME B31.1 rules since the allowables are smaller than ASME I allowables.

Hope it helps.

Ibrahim Demir

 

[davefitz]

There is a saying- if you like to eat sausage, never visit a sausage factory. That philosophy sort of applies to accurate stress analysis of boiler feeders, risers , and downcomers on HRSG's , based on field data from thermocouples monitored during a fast cold startup.

The CTG discharge gas temperature can increase very quickly, and if there is cold water in the evaporator and drums during a cold startup, the thremocouple data indicates taht there is large temperature differntials between ech bank's feeders, risers, and some downcomers, depending on how the boiler mfr configured the circulation system.

So, if you want a simple and easy stress analysis of these components, never review the thernocouple data of a fast cold startup of a HRSG.