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Sunday, June 8, 2008

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Pump efficiency can be estimated as discussed in "Pump Efficiency Estimation Without Vendor Information". The equation proposed in this post has maximum pump head of 300 feet and maximum flow of 1000 gpm. How to estimate pump efficiency for pump head and flow exceeded above limitation ?

Following is a pump efficiency versus Specific speed (Ns) curve may be used when information from vendor is not available.

Source : Randall Pump Handbooks (Click to view large image)


Specific speed can be calculated base on following equation :

Ns = n (Q^0.5) / (h^0.75)

where
n = pump rotational speed, rpm
Q = pump flow, gpm
h = pump head, feet

*Based on above efficiency curve, a few criteria can be postulated :
  • Recommended specific speed (Ns) is from 2000 -3000 as the efficiency is maximum in this range.
  • Minimum specific speed (Ns) is 500 with flow more than 100 gpm.
  • For flow less than 100 gpm, lower specific speed (Ns) could be expected. However, pump efficiency drop significantly (less than 50%). A high efficiency pump i.e. reciprocating pump may be considered.
*Updated on June 9, 2008

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posted by Webworm, 1:57 PM

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