Jump to content

Featured Articles

Check out the latest featured articles.

File Library

Check out the latest downloads available in the File Library.

New Article

Product Viscosity vs. Shear

Featured File

Vertical Tank Selection

New Blog Entry

Low Flow in Pipes- posted in Ankur's blog


Loss Of Pump Discharge Pressure

pump flow pump suction design troubleshooting

4 replies to this topic
Share this topic:
| More

#1 emma14778


    Brand New Member

  • Members
  • 9 posts

Posted 23 November 2017 - 01:29 PM

We have a water pump which has about 90% of its feed from one source (Stream A) and 10%  from another (Stream B). There is a tee about 5m before the suction of the pump.


Recently we had a failure on stream B which resulted in losing the full 10% flow. There were minimal changes in suction pressure but we lost 40% of our discharge pressure and flow dropped by about 20%. As far as I can tell we didn't reach any cavitation, the NPSHr (0.8m) is significantly lower than the NPSHa (13m).


Is it expected that a sudden loss of 10% of your feed would result in such drastic discharge pressure loss and loss in flow? I would have expected to temporarily lose the 10% of the flow but no more. Can this be defined as cavitation or is it something else I am unaware of? The main source of liquid comes from a vessel which has enough inventory to compensate for the loss in flow.





#2 villivord


    Junior Member

  • Members
  • 13 posts

Posted 23 November 2017 - 02:56 PM

You mention a flow reduction of 20%. Look at the relationship between pressure drop and flow (Darcy-Weisbach) which will explain the 40% reduction in discharge pressure. This can also be seen from your system curve, if available. The minimal changes in suction pressure sounds logic as I assume the system between the sources and pump is small compared to the system on the discharge side. 


How do you know source B is only 10% of the incoming feed? 

Edited by villivord, 23 November 2017 - 03:01 PM.

#3 Bobby Strain

Bobby Strain

    Gold Member

  • Members
  • 2,941 posts

Posted 23 November 2017 - 05:55 PM

If you post a sketch with details maybe someone can help. And pump information.



Edited by Bobby Strain, 24 November 2017 - 10:23 AM.

#4 breizh


    Gold Member

  • Forum Moderator
  • 4,890 posts

Posted 25 November 2017 - 04:38 AM

HI Emily,

You can download for free on internet PSIM , a nice software to simulate your system .

I's a great tool , you can build your system using the examples available and test different cases.




Hope this could help you .

Good luck.



Edited by breizh, 25 November 2017 - 05:01 AM.

#5 spchauhan12


    Veteran Member

  • Members
  • 43 posts

Posted 25 November 2017 - 05:34 AM

Dear Forum members,



                       Is System Curve required for AODD Pump (Air- operated double diaphragm Pump)  ?



As per my knowledge, I know this is required for Centrifugal Pump to find out resistance in flow system for corresponding flow values for a


given pipe size.


I have done many Hydraulic calculations for Centrifugal Pumps & AODD Pump in my past porjects, but never drawn system resistance


curve for AODD Pump.


Any co-operation towards this end would be highly appreciated.





Similar Topics