×
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

Flow Rate question on water transfer line

Flow Rate question on water transfer line

Flow Rate question on water transfer line

(OP)
In a ZLD combined cycle water plant, a problem is occuring in achieving flow rate for a gravity filter backwash sump being piped back to a clarifier for water processing.  There are two pumps rated at 250 GPM hooked in parallel driving the backwash water.  The run is approximately 300 feet and has 12 90 degree bends.  The backwash water line is 4 inch carbon steel with no corrosion on the pipe.  The pipe flow meter reads 180 GPM, while 250 is needed to empty the sump fast enough for filter backwashing.  Another restriction on the pipe is that the pipe narrows into a 2 inch control valve.  Thinking the valve restricted the flow it was bypassed with a 3 inch carbon steel line.  This increased the flow 15 GPM but still not enough to empty the sump.  Also, the backwash pipe dumps into a clarifier feed water pipe flowing at 3600 GPM.  Curious if anybody knew if the 300 feet and 12 90's is enough to lower the flow rate or perhaps something else is causing this drop.  I am a new graduate and can not seem to figure it out.

RE: Flow Rate question on water transfer line

What head does the pump curve give at 250 GPM?
What head does the pump curve give at 180 GPM?
What is the actual delivery pressure on the pumps?
What is the change in static head?
What type of control valve?
What is the pressure where the 4" line dumps into the 3600 GPM line?
Was 250 GPM ever achieved, or is this a "day one" problem?
 

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

RE: Flow Rate question on water transfer line

Just to reiterate katmar's post, a flow "rating" has no meaning except at a certain pressure.

I'm just a civil engineer, but you have to plot your system curve (the total static plus friction head at a range of flows) on top of your pump curve.

Theoretically, the pump will discharge the flow noted at the intersection of the pump curve and the system curve.

When you have two pumps in parallel, the combined pump curve will have twice the flow at the same head as one pump.

Then plot your system curve and the pump curve, you can see whether the pump is theoretically sufficient to discharge the design flow.

If it is theoretically sufficient, there may be something wrong with the pump.

If it is not theoretically sufficient, you will have to change your system or get new pumps.

Hopefully some of the real pump engineers will have more information.
I just spec pumps for pumping sewage.
 

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