shuttle valve issue subsea 1

[Initec]

I have an issue with a flood valve design...

We send pipe subsea that has an end closure on each end of the pipe.

The end closures are designed to prevent water from enterying during pipe deployment

-AND-

Flood the valve once the pipe is installed.

We flood the pipe via a shuttle valve design on the end closure...

The shuttle valve is comprised of a body that has a bore in it and fits down into the pipe.

Inside of the body is a "shuttle" that can be pushed and pulled inside of the body. The shuttle has a hole in one end of it and is plugged on the other end.

Once the shuttle is pulled where the hole in the shuttle is aligned with the hole in the body the pipe is flooded with water.

Here's the problem...

The robot (we're subsea remember) pulls the shuttle and and once the hole in the shuttle is only partilally aligned with the hole in the body (cracked open), the shuttle becomes stuck until the pipe is flooded. Once pressure is equalized we can get it off. So we can never fully open the shuttle, only partially.

Why does it get stuck and why can't we fully open the valve?

 

[MikeHalloran]

I don't have a real good mental picture of the mechanism you're describing, but here goes...

As soon as there's a flow path into the interior of the pipe, thanks to the pressure difference, there's a huge flow rate, and that induces radial forces on the shuttle. I'm guessing the flow forces are unbalanced, so the shuttle is forced hard against the body until the flow abates. As a first step, consider a shuttle with two side holes, symmetrically opposite.




Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[Initec]

MikeHalloran, Thank you for the response. What you said is how I approached the problem.

I've redesigned it to use a "pressure balance" concept so that flow is coming in from both sides of the part. I've got a cross section of the new design with FBD and analyses I'd like to show you for comment. Do you know how I can do this?

I want to make sure I've really solved the issue and not introduced more potential for problems.

Thank You

 

[MikeHalloran]

It would be a violation of Eng-Tips forum rules to post my email address, but I'm not that hard to find.

When I'm not at work, I hang out in Compuserve's Careers Forum. That's two ways you can contact me.





Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA