6 replies to this topic

[Sansan]

Have a good day everyone!

 

I have a project to design API675 pump.

 

Based on API675 NPSHa calculation, i calculated NPSHa.

 

 

 

But, NPSHa is  resulted negative number.

 

So, i reviewed calculation and have one question.

 

If the pipe system is same as below picture, how to calculate pressure loss due to acceleration?

 

 

 

In my opinion, L calculating for pressure loss due to acceleration shall only involve horizontal pipe line, not vertical pipe line, as gravity primarily acts along the vertical axis.

 

Could you please review this and let me know if my understanding is correct?

 

Thanks for advanced.

 

 

 

[breizh]

Hi,

No picture!

Breizh

[latexman]

Yes, no picture attached!  Click on "More Reply Options (or "Use Full Editor" during an edit), and the attachment functions are under the text box.

 

Acceleration losses due to pulsations (like in some PD pumps) were not covered in my BSChE education 45 years ago.  It is something I learned from my co-workers and pump vendors.  I have an old installation manual from Wanner Engineering's HydraCell G25 pump that speaks to acceleration losses.  I will attach it.

 

 HydraCell Installation Manual G25-991-2400.pdf   1.12MB   10 downloads

 

In the PDF, search for the word "acceleration".  You want pages 6-7.

 

IIRC, Wanner used to offer an Excel spreadsheet to calculate NPSH and it had acceleration losses in it.  Contact your vendor and see if they have a tool for your use!

[breizh]

Hi,

Same vein:

https://www.pumpsand...t-be-calculated

 

L is the length of the suction line (actual) 

Good luck

Breizh

[Sansan]

Hi,

Same vein:

https://www.pumpsand...t-be-calculated

 

L is the length of the suction line (actual) 

Good luck

Breizh

Thank you for your reply.

 

I understand vertical pipe line shall be involved to 'actual length of suction line' at the link what you recommend.

Is it right what you say to me?

 

Thank you for your kindly comment.

[latexman]

While vertical sections of pipe do affect the "head" requirement of a pump due to elevation and potential energy differences (Bernoulli equation), they experience frictional and acceleration losses just like the horizontal sections.  Use total actual length to estimate frictional and acceleration losses.

[Sansan]

While vertical sections of pipe do affect the "head" requirement of a pump due to elevation and potential energy differences (Bernoulli equation), they experience frictional and acceleration losses just like the horizontal sections.  Use total actual length to estimate frictional and acceleration losses.

Thank you for your reply.

 

I will discuss this matter with my co-worker.

 

Thank you!