Analysis Problem in Hydro Case

I have analysed a High pressure & Temp. piping system consisting of Hydro,Ope,Sus & OCC load cases as per B31.1. In Every case the movements are downward in all the Hangers except Hydro condition. In Hydro condition, I am observed the displacements are upward in many cases not all. I donot understand why it is happening. Anyone can give an explanation ?

Thanks
Tushar

Take note. In your hydrotest case, spring hangers will be considered as rigid supports.

Flexy,

This is correct that in hydrotest case, spring hangers will be considered as rigid supports. But How am I getting Upward movements at Hydro? The movements at hanger points should be zero. In sustained condition, I am getting all are downward movements at hanger locations. So at Hydro, those hanger movements should be zero, instead an upward movement.

Is there anywhere I have made any mistake? Presently i could not able to find out the solution for this.

Thanks
Tushar

I am not sure if you made a mistake. One way to check is to click CAESAR recommended load case combination, hydrotest load case should be in your combination by default if you have inputed hydrotest pressure values in the spreadsheet.

Check if the support location are still lifting, then will proceed.

Goodluck!

Your system may not be supported at the proper/balanced locations. Look at supports offset from long risers or heavy valves. "Teeter-totter" (see-saw) effects will be more pronounced in a hydro case, in particular for large diameter piping. If you attach a CII iso plot showing supports and springs, unstable systems may be obvious to experienced stress personnel.

Thanks Flexy. I have run the system as per Caesar default load cases and the movements at hangers are zero in hydro case.Again I have built the required load cases as per the requirement and the system is balanced now.

Thanks Bob. Yes, there are heavy valves and all are large diameter piping. I have noticed it.

Thanks to all.

Keep in mind that no matter how experienced we are... never forget the basics... jumping to conclusions without checking with the basics will lead you to nowhere, making things more complicated....

Goodluck!