×
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

variable suction conditions

variable suction conditions

variable suction conditions

(OP)
Hi
My water supply for a land development project is described below:
Potable water supply from a 18 in. aqueduct
For 2 weeks per year during maintenance, positive suction is 15 - 20 psi
For 50 weeks per year, positive suction is 90 - 120 psi
Discharge head is 160 psi, discharging directly into a potable water reservoir

Initial minimum discharge is 475 USgpm (first 2 years or so), but since I'm only filling a tank once a day, this can be done in a shorter period at higher flow
Ultimate discharge (about year 6) is 1650 USgpm
I was going to use 1 pump initially (with one back-up pump on standby), with a second and third added in years 2 and 4
My pump suppliers tell me that due to the range in suction conditions, variable speed drives is the only way it can be done.
Can anyone think of another way?
Also, re the piping layout, I initially laid it out with suction and discharge headers in the station and the pumps between them, all in one plane. I've since thought more about putting the discharge manifold above the suction manifold to economize space. Are there any drawing resources available showing different station lay outs which I can have a look at?

Thanks.

RE: variable suction conditions

How your suction pressure gets varied and what type of pumps you have? As the suction pressure is varying greatly, you can make better use of it if you go for variable speed arrangement.

During high suction pressure period, your pump runs to right of the curve (i.e discharges more and draws up more power) and may overload your motor.

If you don't want to spend more, either you have to control the discharge valve (which results in more frictional losses) or go for a second impeller to suit your requirement. (but this depends upon the pump you selected and may not be practical with such a wide pressure range)

Layout is a trade off between space and pressure loss. Anyhow you should give the details of the pump.

RE: variable suction conditions

I'd build a manifold arrangement that lets the standby pump act as a booster into the second pump during the maintenance period.  Look at the pump curves and see if it can do 15 to 90 psig and design your main pump to always do 90 to 160 psig.  As demand grows alternate adding pumps to the standby header and the main header.  When maintenance is not being done have them all on the main service.  This would require clever valving and piping, but it wouldn't be terribly hard.

David

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

eBook - 10 Reasons to Choose CATIA on the Cloud
To compete in today’s fast-paced and competitive market, smaller and newer firms need a powerful platform that will enable them to compete with bigger players, without the heavy investments needed in computer hardware, software and personnel. Download Now
White Paper - Smart Manufacturing for Electronics
This white paper describes a transformative approach to electronics manufacturing made possible by the addition of Mentor Graphics to the Siemens family. It describes a completely digitalized strategy that supports both printed circuit board (PCB) and mechanical design and manufacturing, uniting the entire product lifecycle – from idea and production to customers and back. 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