Hi Richard
I am modelling a piping system with pumps connexion ( triplex pumps discharge & suction connexion). the pumps manufacturing advised to have a flexible hose connexion in order to minimize the vibration effects ,

So i model the piping system up to the pipe/hose connection , free end ,
i analyse only the displacement ,because there is no reaction into pumps connexion to analyse ( the system is totaly isolated)

but my client want to model the flexible hose with the piping system and a anchrage in the pumps connexion.

1- is it true my modelling ???
2- if not true how can i model the flexible hose in the caesar ii piping system modelling


thank you in advance

Hello,

This is usually the challenge in analyzing piping system with flexible hose because usually I've heard from other colleagues that it's hard to obtain stiffness values from manufacturer unlike expansion joints although I haven't tried analyzing piping with flexible hose.

But you can try asking the manufacturer if they can give you stiffness values and input in Caesar model.. I've heard from other colleagues that maybe you can assign some stiffness but I don't know how to justify such values.. Or you can comment on the Technical Bid Evaluation that manufacturer should provide stiffness values as part of their deliverable. This is only good if you are still on the upfront part of the project. But if you are already on the middle part of the project in which a vendor has already been chosen then asking the vendor for this stiffness might be a cost adder depends on the vendor.

Good luck and give us some news what happens. I'm also interested because we are bidding on one project with flexible hose for tank settlement which I don't know will work. They say it's working on their existing plants. I'll see for myself in case we do this job.

Cheers....

@ BORZKI thank you;

but as you know the flexible hose stiffness is so much less than the pipe stiffness so there is no effect on the pipe system , i think that model with flexible not required .

NB: i ascked for the flexible hose stifness form vendor but no response.

Use the [Search] feature here (upper right corner of the Forum), you'll find earlier posts on flexible hose modeling.

THANK YOU RICHARD ,

you mean this topic
http://65.57.255.42/ubbthreads/ubbthreads.php?ubb=showflat&Number=911
""""""
There are two points to consider here:
1) Piping programs, such as CAESAR II, utilize the 3D Beam Element. As such, you can't ask these programs to evaluate behavior that is beyond the capabilities of this element - small deflections, small angles, dominated by bending. You can't model a flexible hose with a 3D beam element.

2) The stiffness of the flexible hose is so much less than that of the pipe, it (the flexible hose) has no effect on the pipe system. Therefore, you can model the system up to the pipe/hose connection, and stop. The pipe has essentially a free end.

If you are concerned about the behavior of the flexible hose, you will need to consult the hose manufacturer for details and recommended practices. You can not evaluate flexible hose in CAESAR II.
"""""

i think yes there is no Force/moment to transmit by the flexible hose but what about the pressure thrust effect .

Regards

In my opinion, the design of flex hose is constrained by geometry, not strength.
I would start by modeling the connection as a free end and ensure that the hose length is long enough to accommodate that free deflection - geometry.
Then, "estimate" hose stiffness for that motion and make sure that a caluclated (F=kx) "free end" load is inconsequential.