Axial expansion joint and Cold pull - pump nozzle

[tomislav.begic]

Hello,

I am doing an analysis of a series of pump systems with hot oil (340°C, 4 bar(g)). In almost every system the axial load on the pump nozzle is bigger than allowed just from the reaction force on the axial expansion joint bellow.

Is it realistic to use pretensioning of the expansion joint to counter/reduce this forces on the pump nozzle?

Kaltvorspannung_Stutzen.png

[private]

Hi

Depending on the pressure, axial expansion joints are often not designed to take the internal pressure reaction force that is created at design pressure.
If you use a cold pull (shortening the pipe) you are actually hoping to make the expansion bellow take the internal pressure reaction force.
In the pressure-less situation you would then get the inverse pull on the pump nozzle.
So generally this is not the best solution. Maybe it can be used in border-line cases where the overload is only marignal.

The internal pressure reaction force will be acting partially on the nozzle and partially inside the pump on the body.
For more detail see this post:

viewtopic.php?p=1683

sometimes it is acceptable to consider only the part that comes from the ring surface.
This is a question that needs to be put to the pump manufacturer.

In other cases especially with higher pressures, the compensation needs to be done with lateral or angular expansion joints which have tie rods and don't release the internal pressure force.

Best regards

Private

[tomislav.begic]

Hello,

Thank you for your answer.

I agree, but the bellow will take only a part of the reaction force.
Isn't this something what the expansion joint is designed for - and is actually recommended, to cold pull the pipe to have an even expansion/contraction of the bellow?

Cold_pull_expansionjoint.png

Inverse pull will occur during assembly phase and in the pressure-less situation, but if the overall loads on the pump are less then before, then I do not see this as a problem?

I am aware this is not the best solution, but this is existing system so I am seeking for a solution without redesigning the whole system. I really do not have much options here, so first I want to see if this is even a solution to consider regarding pipeline guidelines/restrictions and thoughts from more experienced engineers

As for the load on the pump body: This is something I have been told before to check and will try to get an answer from the manufacturer.

Thank you for your time and kind regards!

Tomislav