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


pH and abrasives effects on choosing pump construction

pH and abrasives effects on choosing pump construction

pH and abrasives effects on choosing pump construction

We have several self-priming stainless centrifugal pumps that have been running for 15 years and have given us very little trouble.  I do not have nuts and bolts flying into the impeller, but I do have a Manganese Dioxide powder as well as plastic pellets (and the occasional plastic trash in any wastewater system).  We treat this wastewater for pH, hence the pH can swing from 6-9, rarely as low as 4 and sometimes as high as 10 or 11.  What material of construction would be most appropriate here since I need to upgrade these pumps?  My first thought is to go with what has worked for years, however, if I can save some money by going with ductile iron or carbon I would prefer that route.  The flow is ~180 GPM @86 FT TDH.
Also, in order to improve my NPSHA (suction pressure is only 7-8 PSIA)would moving the suction strainer to the discharge be unwise in that I could plug/ruin the impeller/pump?

RE: pH and abrasives effects on choosing pump construction

15 years pumping the crap you are is a long time. It ain't broke........

RE: pH and abrasives effects on choosing pump construction

You may want to give due consideration to non-metallic pumps.  Be sure to clearly state all expected conditions to the pump manufacturers and to require performance and durability guarantees.

Suction strainers are called that for the obvious reason.  If NPSHa is a problem, can the pump elevation or the suction pipe size be changed?

RE: pH and abrasives effects on choosing pump construction

How close to the required NPSH is "too close".  If I have 16 FT and the pump requires say 12-14 should I look at a different design?

RE: pH and abrasives effects on choosing pump construction


The 12-14 ft NPSHr probably represents pump operation with 3% head loss to cavitation, so operation at 16 NPSHa does not present much of a favorable margin.  I would want to consider other pumps and system configurations if possible.

RE: pH and abrasives effects on choosing pump construction

Fortunately the flowrate range I'm looking at 200-250 GPM and the pump sizes do not require NPSHr much past ~7-8 ft.  Thanks for the input.  This is one area in which I'm still getting a feel for.

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


White Paper - The Evolving Landscape of Commercial Battery-Powered Trucks
What’s driving the evolving landscape of truck electrification? What are the barriers, motivators and strategies for accelerating the electric transition? What insights and resources are available for today’s design engineers working to achieve industry disruption and evolution? For answers to these and other pertinent questions, read this white paper. Download Now
eBook - Rethink Your PLM
A lot has changed since the 90s. You don't surf the Web using dial-up anymore, so why are you still using a legacy PLM solution that's blocking your ability to innovate? To develop and launch products today, you need a flexible, cloud-based PLM, not a solution that's stuck in the past. 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