Hi all,

I'm modelling a cooling plant where different pupms are installed with antivibration joint
(see sketch or click on mve mve)

In the sketch there are two pumps and each pump has two rubber joints, one for the suction nozzle (horizontal) and another for the discharge nozzle(vertical)

I found the joint used in the cooling plant I'm analyzing.

FSFA 16" rubber joint on this catalogue:
http://www.emiflex.eu/sites/default/files/RUBBER_JOINTS.pdf

My question is:

How to model correctly this kind of joint? or the best way to model it? What about stiffnesses?


Other informations:
Design temperature 80°C
Design pressure 10.4 bar
Stifnesses on the image are in N/mm


Thanks.

You should model a rubber joint just like you would model a metal joint and as discussed in the users manual. In regard to the spring rates, unfortunately most rubber manufacturers don't provide these values because they are so low and normally not a factor. You could contact the manufacturer with a request or just assume some low values.

Do the joints have the optional tie rods across the joints? If no, then you'll be exposing your system to the longitudinal pressure thrust. If yes, then the joints will only take lateral movement.

Thanks Dan,

I read the user manual and modeled the joint as for it. Now I'm concerned about a problem: the joints in my plant have no tie rods and looking through this forum I read about the pressure thrust "issue", so I considered this pressure thrust inserting the effective ID in the expansion joint toolbox and supporting properly the pipe near the pump nozzles.

All the system is verified but when I try to verify the pumps using the API 610 module (as can be easely foreseen) there are huge loads due to this pressure thrust at suction and discharge nozzle, and these loads are greater than the API allowable ones.

How can I justify this to the client?

Is this new construction or an existing system?

If existing, you might be able to justify it based upon past experience assuming that the pumps have been operating properly without high maintenance costs. Excessive forces on a pump often cause bearing and alignment problems resulting in high maintenance costs.

No, the system is new.

I'm making stress analysis of lines that are connected to these pumps but I don't know how to verify the pumps using API 610 module including the pressure thrust due to EJ (effective ID) with no tie rod.

Hi, I am unable to download the system Snap, can you repost it?

Regards,
R.K.

Since this is a new system, the pressure thrust & API 610 are applicable and you probably should NOT use an unrestrained joint. I'd recommend you look at putting tie rods across the joint to eliminate the pressure thrust and axial & angular movement capability. Then locate your joint perpendicular to the major system movement to absorb it in lateral movement.