×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

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!

*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

Discharge Static Head

Discharge Static Head

Discharge Static Head

(OP)
Good morning. I haven't been able to get this question answered with a moderate amount of research, but it's always bothered me. When working with pumping systems, specifically wastewater lift stations, the discharge static head is generally defined as the elevation difference between the discharge liquid elevation and the centerline of the impellor. My question is, should additional head be added if the pipeline dips below the impellor level or rises above the discharge liquid level? It seems to me that things should have an effect. I've included a sketch to accompany my question. Would the discharge static head be A, B, or C? Or something else that I have not considered.

Thank you in advance.

RE: Discharge Static Head

Option C.

STATIC DISCHARGE HEAD is the vertical distance in feet between the pump centerline and the point of free discharge or the surface of the liquid in the discharge tank.

Note that at startup, the pump must have enough power to lift the water to "B".

RE: Discharge Static Head

except for force mains which flow back down to the tank using gravity as shown in the sketch...

RE: Discharge Static Head


There are two options, A or C..

Try assuming static head is C.. and draw hydraulic gradient line ( Z+ P/γ ).. If the HGL does not clash with the ( above the hill ) , the assumption Z = C is correct..

If clushes, Z will be A and open channel flow will develop between high point and the reservoir.

RE: Discharge Static Head

You have to analyze the start up condition (A) and the pressurized full flow (C) condition.

RE: Discharge Static Head

Jgailla seems to be correct in case the distances are short and there is no air valve used at the curve tip location.

In case of long distances and/or there is an air valve used at top of the curve I would use A as the discharge head for start up and operation for pressurised full flow.

RE: Discharge Static Head

I actually think you have to design for two conditions (A) start-up and (C) duty. Look at your system curve for the two and size your pump accordingly. At start-up the pump must have enough power to lift the water up the the full height of the hill before it can take advantage of gravity and free-fall down the hill. I would also make sure my check valve is of sufficient size to handle a cascading back-draft of water in case of a power failure or the pump shuts down too quickly. You could also generate sizable negative (vacuum) pressures as well. Of course this all depends on the order of magnitude for elevation change and distances.

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! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close