Hi all,

I used a spring can at the discharge of the pump line. I have a couple of questions regarding the modelling of the spring can in CAESAR II:

1. Since the pipe will slide on the spring can when the pipe is hot, there should be a friction force. It seems CAESAR doesn't consider this friction force. Don't know if I am right or not on this.

2. The calculated pipe movement in Y direction at the spring can is higher than it should be which causes +Y force at the pump nozzle in the oprerating condition (the spring can is designed for hot load). Is this right? How to reduce this +Y force at the nozzle by modelling the spring can?

1) There is an example, in the Applications Guide, of how to model a "spring can with friction".

2) If the displacement is more than you can tolerate, you have to change something. Move supports, or reroute the pipe. (I presume you've checked everything else for correctness?)

Thanks Richard,

For the displacement, I mean the displacement in the Y direction is more with a spring can than that without the spring can. For example, for the sustained case, dy = 0 with a +Y support, when I change the +Y support to a spring can, dy becomes 0.224mm. Is it because of the spring?

It could be, remember the spring only balances the system in one (single) position (load case). For all other positions (load cases) the spring and system are not in balance.

You mean at which point. At hanger location?

If you want to balance at hanger location,
First run the system with +Y support at hanger location.
From output read SUS load at +Y support and
Impose it as theoretical cold load and set appropriate stiffness and rerun the analysis.

The "system" is balanced at "one" position of the hanger. As soon as anything changes (think a different load case), the system experiences a different deflected shape, the load on the hanger changes, as well as the loads everywhere else.

Yes, I had mentioned the approach to balance at SUS condition to obtain a zero deflection in sustained case.
May be I could have mentioned it.
Deflection at other load cases will make the the hanger location "unbalanced".
Thanks Richard.

We assume that the first 1/4" of lateral movement at a can spring is frictionless, that there is that much "play" before load column meets the spring housing.