Hi,

I am working in a stress analysis model in which there is an occasional load that can happen only at a temperature of 200F, but the maximum operating temperature of the line is 700F. The applicable code is B31.1.

Such code defines the allowable stress for occasional loads as KSh and defines Sh (104.8.1) as "basic material allowable stress at maximum temperature".

I am wondering if Sh should be taken at 200F (the temperature of the oine when that occasional load is going to happen) or 700F (the maximum temperature of the line while in operation although not simultaneous with the occasional load).

I would say that it should be 200F but the code is not that clear. Any thoughts in this regard?

Thank you.

Hi Baboo
By default caesar pick lowst value of Sh among the different temperature input. However if you got confirmation from authentic & approved sourse that occasional case is occouring at 200F only you may make another caesar copy caesar file keeping only 200 deg F temperature. But please be remind that it is quite dengarous solution. You may need to consult pipe stress lead & project manager for their prior approval.

Regards

Habib

Occasional loads are considered in the analysis because of their unpredictive nature of happening but ofcourse their cycle of occurance can vary alot. So I would say if your operating temp is 700F than it is more likely that Occasional load will occur during operation at 700F. Take Sh at 700F for OCC loads.

If by any means your plant process is limited to few minutes of 700F operation and mostly operate at 200F; In that case you might use the Sh at 200F for occasional load.

Seismic as well as wind (OCC loads) can occur at any time so be careful regardless of how you are analyzing the system.

Regards,
Salz