3D

What you are describing is called "rail extruding" and photoshop does not have that capability.

You will need a dedicated 3d app to create your object.

Depending on the actual curvature of the path you could possibly fake it with Repoussé's deformation options, but otherwise it is as Silkrooster said. That aside, if it's realyl just a simple tube thingy, I can imagine a million easy ways to just draw it with otehr tools...

Mylenium

All you need is some vector paths/ shape layers then you can do Path --> Edit --> Stroke or  use Shape Layers with Stroke layer style. The arrows and circles are easily drawn using the shape tool in shape layer mode, then transformed into place using free transform. Refine with whatever layer styles you can imagine to add shading gradients or whatever...

Mylenium

Hi,

As already mentioned, you are limited if you want to just use the 3D features in CS5. You can use Repoussé (Help link) to extrude a circular path/shape and then bend the extrusion path on an arc. Here's a Ps CS6 rendering (customized options w/transparency, IBL, and line illustration)  but can be equally accomplished in CS5:

Ps CS6 has improvements that make it easier to contruct a multi-bend tube, but it's still not as fluid as "extrusion on an arbitrary path". Here's a fairly quick construct of 2 bent pipes merged together and aligned.

regards,

steve