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


2 pumps in parallel with one recycle line

2 pumps in parallel with one recycle line

2 pumps in parallel with one recycle line

can anyone tell me what will happen at low flow if 2x100% centrifugal pumps are operated in parallel but with a single recycle line (that is sized for single pump recycle capacity)at the common discharge line? could one pump cavitate while the other operates satisfactory?

RE: 2 pumps in parallel with one recycle line

Many re-circ lines are grossly oversized, but each pump should have it's own line back to the tank. If the re-circ line is on the common header, then it's after the isolation valves for each individual pump. It should be connected before the isolation valves.

It's not really a cavitation issue, it's to prevent the pump from overheating. I've seen a fire pump handling cold lake water actually blister the paint, it got so hot. There have been cases of pumps exploding from operating without flow for short periods of time.

RE: 2 pumps in parallel with one recycle line

Be careful when operating pumps in parallel without dedicated min flow lines on each pump.

Imagine two pumps in parallel, each one operating back to the left of the curve.  Now, no two pumps will have the same performance curve and, thus, one of the two pumps will have a slightly higher head than the other.  In this case, if you have check valves at the discharge of each pump, the pump with the higher head could close the check valve of the other pump causing it to deadhead.

Best practice is to put the min flow recirc line IMMEDIATELY after the pump (before any valves).  You can combine the min flow lines downstream of that point if you want and terminate that line in your DA tank.

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 Criticality of the E/E Architecture
Modern vehicles are highly sophisticated systems incorporating electrical, electronic, software and mechanical components. Mechanical systems are giving way to advanced software and electronic devices, driving automakers to innovate and differentiate their vehicles via the electric and electronic (E/E) architecture. As the pace of change accelerates, automotive companies need to evolve their development processes to deliver and maximize the value of these architectures. Download Now
White Paper - Model Based Engineering for Wire Harness Manufacturing
Modern cars, trucks, and other vehicles feature an ever-increasing number of sophisticated electrical and electronic features, placing a larger burden on the wiring harness that enables these new features. As complexity rises, current harness manufacturing methods are struggling to keep pace due to manual data exchanges and the inability to capture tribal knowledge. A model-based wire harness manufacturing engineering flow automates data exchange and captures tribal knowledge through design rules to help harness manufacturers improve harness quality and boost efficiency. Download Now
White Paper - Modeling and Optimizing Wire Harness Costs for Variation Complexity
This paper will focus on the quantification of the complexity related costs in harness variations in order to model them, allowing automated algorithms to optimize for these costs. A number of real world examples will be provided as well. Since no two businesses are alike, it is the aim of this paper to provide the foundational knowledge and methodology so the reader can assess their own business to model how variation complexity costs affect their business. 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