×
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

Calculating slippage for PD pump vs Volumetric efficiency vs NPSHr ?

Calculating slippage for PD pump vs Volumetric efficiency vs NPSHr ?

Calculating slippage for PD pump vs Volumetric efficiency vs NPSHr ?

(OP)
Hi pump Enthusiast,

This is internal gear positive displacement pump,i had probably a misconception between slippage and volumetric efficiency. My understanding that volumetric efficiency could be calculated given the theoritical displacement in term of L / revolution of pump. Assuming a theoritical displacement is 6.9 L/ rev. If the actual pump curve indicate operating at 100 rpm to get 30 m3/hr ( actual flow) then the theoretical volumetric flow is 690 L/ min or 41.4 m3/ hr. Since volumetric efficiency = actual flow / theoretica flow * 100 = 30/41.4 =72 % . My questiion
1. Does this volumetric efficiency of 72% is indicating a slippage of 28%, what is the right way to interprate the volumetric efficiency amd calculating slippage in the pump .

2. Does slippage of pd pump damage
The pump, as the fact for slippage the fluid is just recirculatinf from discharge back to suction and so forth result in heating up the pump

Refer to pg 6 and 7
http://db.tt/2z6SxPPV

3 NPSHr is givem by manufacturer as the minimum
pressure required at the suction . The justification of pressure loss in pD pump can be justified at the throat area of the suction inlet,Rotor and idler void where the flow coresspomding to rpm, the more flow require more pressure and as rotor rotate faster the pressure loss is greater.

Does operating at faster speed and high viscosity requires higher NPSHr so how manufacturer set its NPSHr does it based on the variation of speed and viscosity so assuming NPSHr for thick liquid of 60000 cps may be higher significantly vs 0.3 cp of Toluene or alcohol

This article shows a good NPSH explanation of pd pump

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