×
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

Removal of Impeller

Removal of Impeller

Removal of Impeller

(OP)
In a two stage pump; if the head required can be adequately supplied by one impeller, which impeller should be removed?

RE: Removal of Impeller

my swag, the 2nd stage.

thoughts . . .

1) may have rotor imbalance/stability without 2nd stage impeller . . .

2) 1st stage may be design for low npsh - insufficient details provided.

3) you will likely be better off with pump suited for process conditions; than bastardizing existing pump.

frankly, i'd consult with OEM and obtain there opinion or expertise on the matter.

regardless, good luck!
-pmover

RE: Removal of Impeller

If your system equations equal one pump, then use one pump. Replace the 2nd one with piping and tag it for a spare.

"If A equals success, then the formula is: A = X + Y + Z, X is work. Y is play. Z is keep your mouth shut."
-- by Albert Einstein

RE: Removal of Impeller

I would remove the second impeller, removing the first impeller means the inlet flow to the second impeller will have to travel thru the 1st stage volute discharge opening which leads to the second impeller inlet, this will have the effect of increasing inlet losses.

However, I would check with the manufacturer or agent for their advice on this.

Naresuan University
Phitsanulok
Thailand

RE: Removal of Impeller

agree with artisi

RE: Removal of Impeller

I would slow the motor down some, and wait for demand to go back up.

Mike Halloran
Pembroke Pines, FL, USA

RE: Removal of Impeller

An interesting topic.

When you remove either ist or 2nd stage, which curve do you follow? How do you know one stage is enough?

Or you may think to trim the impellers -- at least you have a curve to follow. -- or replace the pump with a single stage one.

RE: Removal of Impeller

You shouldn't remove either impeller stage if you can avoid it because you may be faced with difficult shaft radial or axial loading and rotordynamics rebalancing problems. The first stage is more important because it is usually designed to meet the cavitation design needs whereas the 2nd stage impeller may not provide features for cavitation control. If you are presently developing twice the needed head, then you are probably operating at a flowrate that is far below the best efficiency point (bep)flowrate but you need to know exactly how far below bep. If operating below manufacturer's recommended minimum flowrate, flow instability is likely to lead to high radial thrust loading and possibly excessive shaft vibrations. If you don't see excessive vibrations then you may be operating below the unstable flow range where continued operation without damage may be possible. Typically, worst instability flowrates are between 30 and 70% of bep flowrate.

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