×
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

Depth of Oil in Sloped Atmospheric Drain Line

Depth of Oil in Sloped Atmospheric Drain Line

Depth of Oil in Sloped Atmospheric Drain Line

(OP)
I have searched for hours now.  This has to have been tackled before.
Knowing my flow rate, the size of my pipe, the specific gravity of my oil (.85) and the slope of the pipe (1/2" per foot) how can I calculate the depth of the oil in the pipe consistently?
API mandates that drain lines on oil systems shall run no more than half full.  How can I calculate the actual depth based on the above criteria accurately?

Mark

RE: Depth of Oil in Sloped Atmospheric Drain Line

Fing a hydraulics textbook, open channel flow.

One approach, the manning's equation:

V=(1.486/n)(R^0.67)(S^0.5)

n for cast iron is 0.015
R is hydraulic radius =Ax-sect/wetted perimeter
Now this is for water, low viscosity, not sure if viscosity effects are significant for your case.

Say your pipe is 4" diam
S=1/2"/ft=1/24=.042
R=(pi*R^2/2)/(pi*R)=R/2=0.083
V=(1.486/.015)*0.166^.67*.042^.5=3.9 ft/sec
Q=VA=3.9*.09=0.34 cfs =150 gpm

Check my math, I was flyin'

Carl


RE: Depth of Oil in Sloped Atmospheric Drain Line

I would NOT use information in the above post without checking the Reynold's number of the flow.  As civil engineers typically work with water, they have a habit of neglecting viscosity.  If your oil is very viscous, you will probably have laminar flow, and the friction factor will be different.

I would assume the pipe is half full.  The hydraulic radius is the flow area divided by the wetted perimeter.  For a half full pipe, this equates to (Pi*R^2/2) / (Pi*R) = R/2, or D/4.  The hydraulic diameter is 4 times the hydraulic radius, or D.  Assume a velocity, V, and calculate your Reynold's number using the hydraulic diameter as described earlier.  The darcy friction factor is then obtained using the Moody chart or Colebrook equation with Reynold's number and absolute roughness as the inputs.  You need to itterate and vary the velocity until the head loss per ft equals the pipe slope.  If the resultant flow rate is adequate, you are done.  If not, try a bigger pipe size.

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