Forces on subsea bushes?

[Waterman47]

Good Day,

I have what may seem like a very trivial question. We are designing a tool that is to work at depths of 3000 metres below sea level. In respect to the bushings, I am saying that the bushes will experience a force of P = density * gravitational constant * depth, because they are operating under water. Using a density of 1050 kg/m^3 because sea water is more dense at those depths, one gets a pressure of 30,9 MPa. In my mind, this has to be added to the stress induced into any bush, correct? My coworkers are trying to argue that the forces cancel out but in my mind, there is no ways. Any object that deep underwater will experience an immense pressure regardless of the fact that is it uniform in cross section and doesn't have an air cavity. Have I lost my mind?

So if they want to use Vesconite, then at almost 31 MPa one is already at the design limit. PEEK is my choice of material but those costs are high. At the price of a vessel running per hour, it is penny wise and pound foolish to have a tool on deck, replacing failed bushes!

Thanks,
Adrian

 

[IRstuff]

You've not given enough information to decide. A drawing is probably required. If the water is surrounding the bushing, then there is no asymmetric stress. Your presumption is only valid if there's no counteracting force.

TTFN
I can do absolutely anything. I'm an expert!
homework forum: //

http://www.engineering.com/AskForum/aff/32.aspx

faq731-376 forum1529

 

[Waterman47]

Ok imagine a block of rubber sitting 3000 metres under water. Surely it is experiencing a compressive force on it all the time, or? For what it's worth as an example, bushings in red.