×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Using Pipe as a Weir

Using Pipe as a Weir

Using Pipe as a Weir

(OP)
How do you calculate the head over a pipe when used as a weir, and at what point does it not fucntion as a weir.

Thanks.

RE: Using Pipe as a Weir

Are you talking about a phase separation application where a pipe comes out of the bottom of a vessel, then does a 180 degree turn and comes straight up to a certain level, then turns 180 again and goes back down, then the height at which the pipe makes the turn from up to down is the height of the liquid in the vessel?

The head at the inlet of the pipe would just be equal to the height of the liquid level in the vessel.  The head at the outlet would be zero, unless the pipe would be liquid full all the time, but then you'd be in danger of creating a siphon and emptying your vessel.  The pipe would have to go up to an overflow pot or something.

OR...

Are you talking about a riser inside a vessel that comes up inside to a certain height?

The head on that one would be zero.

RE: Using Pipe as a Weir

(OP)
For example, a 4" overflow pipe in an elevated storage tank.
If the tank was being filled at 100 gpm and was going past the height of the overflow pipe, what would the head over that pipe be?

I was just emailed some handy graphs on circular weir flow from 1964 by F. Caplan. Wish I knew how to post them.

RE: Using Pipe as a Weir

It is not clear to me whether your overflow pipe is in the side of the vessel, or if it projects up vertically through the bottom of the vessel making a horizontal opening at the top of the pipe, so here are references for both.

For a nozzle in the side of the tank the best reference is  P.D. Hills which was published in Chemical Engineering, Sept 5, 1983, pgs 111-114.

If you are looking at a circular weir formed by the open top of a vertical pipe then an easy-to-find reference is Perry's Chem Eng Handbook. The reference I have here is to the 4th Ed pg 18-9, but I am sure the newer editions will have it too.  The Hills article gives some guidelines on when the head over this type of weir is sufficient to flood it and stop it working as a weir.

Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources