Designing a Cap to Stop Fluid Flow from an Underwater Pipe

[Shaun_W]

"Capping" fluid flow from pipe

If there is a 4.1cm diameter pipe located ~10m underwater, with water (negligible volume and mass flow rates - the water is only really trickling out) flowing out of it at 2 bar (so 1 bar difference in water and ambient pressure), does anyone have any rough ideas for a device I could construct to stop the water from flowing?

A suitable ROV has already been constructed; getting this device or "cap" down there is absolutely no problem. But I am completely baffled as to how to actually go about designing this cap!

Help much appreciated.

 

[Unrest]

Um, just crimp it? The answer depends a lot on the details of the pipe.

I guess if you wanted to be clever you could make some kind of bung that grips onto the inside of the pipe under pressure from the water. I imagine some kind of flexible tube with a closed end. If there's enough tube area, then no matter how high the pressure, the friction to the pipe wall can always exceed the force trying to push it out of the pipe.

Well that's assuming it a competition. Might not be so great in the real world with changing pressures and what not.

 

[Shaun_W]

We're not allowed to crimp it, sorry, should have made the rules clearer in my original post. We've got to design a cap that can be brought down with an ROV, installed, and then left for a little while before being taken off by divers.

I'll look into the bung idea, though, thanks!

 

[Unrest]

Another possible type of device is something like a coil spring or woven tube slid over the pipe. Pushing it on is easy because when you compress it, the diameter increases. But pulling it off can be very hard because as it's stretched in length, it shrinks in diameter.

Basically the same reason you can't pull a condom off directly. Hell, just use a condom! :P

 

[Shaun_W]

I'll do some research into that (the coil spring thing - not the condom!). Pulling it off isn't our problem, thankfully. As long as we don't damage the pipe.

Thanks for your help, mate.

 

[Unrest]

Um, on second thought, I think I've been confusing tension with torsion. Possibly the spring would just pull off coil by coil. However, woven mesh is a different story.