Hello to all,

I have a query on expansion joint thrust force.

I believe the thrust force is generated due to the expansion of the bellows, but if the bellows are to compress, will there still be a thrust force generated?

This brings me to the question of a tie rod having no inside nut, means the bellows cannot expand but can still compress.

Will I still include a thrust force in my design?


Also another question regarding thrust force on equipment, example pumps or vessel.
I believe the thrust force will not act on the nozzle itself, rather it will act on the inside wall of the equipment and its anchor. Do we have to inform the vendor regarding this additional forces for the equipment's anchor?

Thank you all in advance.

1)As per my understanding, Pipe internal pressure will try to open-up the bellow convolutions and thus pressure thrust will always gets generated.

2)As per my knowledge, we should give nozzle/anchor loads to vendor inclusive of this pressure thrust if it is not restrained anywhere in between.

The joys of pressure thrust. I have had many dealing with this wonderful and often misunderstood force.

1. Pressure thrust is always there, especially if you are trying to compress the bellows. Modeling the limit rods that control the expansion will often absorb all the thrust force if the bellows stays fully uncompressed at the rod limits. So if you add the thrust forces at the ends of the bellow element, you will see the forces acting on the control rods equal to those forces if the bellow is fully extended. In cases where the bellows is compressed, you will see those forces elsewhere in the piping.

2. There is a lot of different things I have seen for dealing with thrust force on a nozzle. I have in the past removed the flow path area from the nozzle loads as you are correct that is imparted into the internals of the pump or equipment. In most cases that would be the same as any other non expansion joint system. Most of the time for nozzle allowable load review, I look at just the pressure thrust caused by the bellows and not the through liquid.

I have added a PDF I found very enlightening on this subject.

Thanks,
Duncan

Thank you very much Ankit and Duncan for your reply.