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AODD NPSHa Calculation Validation

AODD NPSHa Calculation Validation

AODD NPSHa Calculation Validation

(OP)
Hi all -

I'm new here, thanks for having me. Looking forward to engaging with you all. Brief background on me: Mechanical Engineering degree (2019), just landed my first role where I can use my education. Role is improving and developing processes to recycle batteries. Currently I am setting up a new line that has a couple AODDs in it and I want to make sure I am not going to burn them out. We are using what we have on hand, and they are way oversized for our needs.

On to the topic of the post - I am hoping someone can confirm I am thinking about NPSHa correctly:

NPSHa=H_abs+H_Static-H_friction-H_acc

H_abs=14.7psi*(2.31ft/1 SG)=33.96ft %tanks are open to atmosphere

H_static=4ft %Fluid level above inlet

H_friction=.7ft/(100ft pipe)*5ft pipe=0.035ft %Short 1.5" dia. run to pump, value pulled from https://www.engineeringtoolbox.com/pvc-pipes-frict...

H_acc=LVnC/Kg=(5ft)(1.6ft/sec⁡ )(.718 cycles/sec⁡ )(.2)/(1.4)(32.174 ft/sec^2⁡ ) ;Hacc= 0.0128ft %.232 gal/cycle on my pump. .2 used for C, 1.4 used for K.

NPSHa=33.96+4-0.035-0.0128;NPSHa=~38ft

NPSHr = ~7 - 8' at my desired flow.

How does this look?

RE: AODD NPSHa Calculation Validation

Vapor pressure subtracted from NPSHA is missing. If your water is ambient temperature, nothing to worry about. I assumed it was water from your 2.31 psi/ft.

Great to see that you have converted all pressures to psia and that you already know about acceleration head requirements. Are you above any pump minimum flow rate requirements?

I think you're off to a good start.
Next time you might want to mention the fluid name and its temperature.

A black swan to a turkey is a white swan to the butcher ... and to Boeing.

RE: AODD NPSHa Calculation Validation

(OP)
Thanks for the tip - I'll add in those details next time. Ambient water is the correct assumption.

Admittedly, I am not familiar with minimum flow requirements for diaphragm pumps. I did not see any listed on the spec sheets.

Below are the pump curves and my duty points.



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