×
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

centrifugal pump efficiency

centrifugal pump efficiency

centrifugal pump efficiency

(OP)
I need to estimate an efficiency of a centrifugal pump, but do not have any specifications.  This is what I know:

Single stage centrifugal pump

Static head:  100m

Motor power:  200 kW

Water quality:  Poor.  Water is pumped from the bottom of a gold mine.  It is not slurry, but it does contain rock particles.

Given the limited information above, what efficiency can I expect? Rough figure such as 30%, or 50% will be sufficient.

Thanks

RE: centrifugal pump efficiency

Given: P = 200 watts = 8850.7 ft.lb/min
       H = 100 meters = 328 ft. head.
assume water is 62.4 lb/ft^3

ft.lb/min (power)= 8850.7 = ft^3/min (flow) x 62.4 x 328 ft/E (efficiency)

8850.7 = 62.4 x flow x 328/E

E = 62.4 x flow x 328/8850.7 = 2.312 x flow

Sorry.  You have 1 equation, 2 unknows.  No unique solution.

 

RE: centrifugal pump efficiency

The efficiency for the pumps, which should be hard metal slurry pumps would be round 50%. Using 200kW flow rate would be somewhere round 100l/s. fairly rought and ready but so is your enquiry.

RE: centrifugal pump efficiency

Is it possible to measure the flow rate and motor amps?  These with the static head would allow the efficiency to be calculated.

RE: centrifugal pump efficiency

Easiest thing to do is go back to the pump vendor and ask for a sales curve for that pump model and running speed.

If you really want to do some calcs and "play around" (that's what I call it) with some numbers go look at the pump name plate.

You can measure motor amps to give you and idea where you're at on % load relative to motor FLA. In pump applications typically motors are sized so the max BHP (and FLA) coincides with ~120% of rated flow. If you're just under motor FLA then you can assume you're at or near rated flow (name plate flow). Use that flow and head to calculate a Specific Speed (not pump RPM... Google it if you don't understand) for that impeller. Use that specific speed number to search online for a pump OEM's sales curve for a similar pump design and application. Compare the head/flow they give for your impeller diameter (also on the name plate) to your "assumed" head/flow.
 

 

RE: centrifugal pump efficiency

efficiency=(H x Q x Specific Gravity) / (3960 x BHp)
units:ft, gpm, Hp
You should measure the flow rate, and the BHp at this flow (by measuring the amper)and specific gravity of pumped fluid and then simply use above equation.

Reza

RE: centrifugal pump efficiency

rshayesteh,

In this case I think he would get a divide by zero error.

"I'm all in favor of keeping dangerous weapons out of the hands of fools. Let's start with typewriters."
- Frank Lloyd Wright (1868-1959)

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