Advantages of Trunnion Pipe Supports

[Ask1122]

Hi all, can someone please tell me what are the advantages of using a trunnion pipe support? I guess that since it is welded on the pipe, it will prevent pipe movements in any directions, but then why would you use a trunnion instead of an anchor?

Thank you!

 

[minger]

We use trunnion supports a lot for our engine mounts. The nice thing about trunnion mounts is that they don't over constrain. They restrict all displacements, but not all moments. You can add a simple steady-rest at the back to grab the final degree of freedom.

I am not real familiar with piping supports, but I hope we're talking about the same thing.

 

[Ask1122]

Thanks for the reply, but I am not sure how it restrict only the displacements but not the moment?

 

[minger]

These are what we call trunnion mounts
http://en.wikipedia.org/wiki/File:Belarus-Vitsebsk-Monument_to_Heroes_of_Patriotic_War_of_1812-6.jpg

...mostly. The engine usually has the female end, basically just a hollow support. A pin of some sort is typically inserted into them that allows them to rotating in the pins axial direction. They prevent yawing and rolling, but not pitching.

We typically only restrict sideways motion on one of them, and they both restrict displacement in the vertical and axial directions. That leaves only one DOF left, which we use a "kind-of-pinned" joint at some aft location.

We use them because we can prevent over-constraining our part.