How to operate pumping system efficiently?

Last updated on February 27th, 2021 at 02:20 pm

Pumping system operating efficient operation is important to reduce operating power cost. Considering a typical 5 year lifecycle of 100KW and above pumps, spent on power contributes to more than 90% of total ownership cost. Therefore it is important to consider operating efficiency of pump. Pump efficiency is always a major consideration while pump procurement, but because of no of reasons in many cases pump efficiency drops while operation. lets check, How to operate pumping system efficiently.

Centrifugal Pump
Reason for efficiency drop can broadly be divided in two categories:-
  1. Best efficiency point shift as per system requirement.
  2. Pump efficiency deterioration.
Let us try to estimate pump operating efficiency step by step:

STEP-1 Measure and collect pump system data as below

  1. Operating Flow
  2. Operating differential Head. (Discharge head – suction head)
  3. Fluid type
  4. Motor power withdrawn and shaft power.
  5. Pump curve

STEP-2 , After collecting data measure pump efficiency

 Efficiency of pump is calculated by

Pump efficiency                = Ph(kw) / Ps(KW) X 100

Where, Ph(kwis hydraulic power &  Ps(KW) is shaft power

Hydraulic power

Ph (KW) = ( (Sprg X Q ) X H X g) / 3600

  • Q = capacity in m3 / hr
    • spgr = specific gravity (water =1)
    • H = differential head in mtr
    • g = gravitational acceleration in m / sec 2 (g=9.8)

Ps (KW) = motor measured power X motor efficiency

STEP 3 Example with a typical pump data

Data collected as per below format and pump efficiency calculation

Sr. No Description Unit Design Operational
1 Pump Flow M3/hr 1200 750
2 Spgr   1 1
3 Differential head Mtr 30 37
4 Power KWhr 113.5 109
5 Pump efficiency % 86.5 74.5
6 Efficiency loss %   12
Table A

Pump flow 750 m3/hr,

Differential head = 37 mtr,

Measured power = 109 KW

Motor efficiency = 93%.

Ph (KW) = 750X37X9.8/3600 = 75.54 KW

Ps (KW) = 109X.93 = 101.37 KW

Pump efficiency =75.54 / 101.37 =74.5%

STEP 4 Identification of Problem

Sr. No. Case Condition Reason for efficiency drop
1. Pump efficiency is low If pump flow, head and power follows pump characteristics curve. Best efficiency point shift as per system requirement.
2 Pump efficiency is low If pump flow, head and power does not follows pump characteristics curve. Pump efficiency deterioration
Table B


STEP 5. Solution to pump efficiency drop

Sr. No Reason for efficiency drop Condition Solution Disclaimer
1 Best efficiency point shift as per system requirement.     Flow is high, Head is low Pump needs to be replaced with suitable design.  
2 Best efficiency point shift as per system requirement.   Flow is low (constant) , head is high Impeller trimming may be done. Impeller tripping will shift pump operating condition to Best efficiency point
3 Best efficiency point shift as per system requirement.   Flow is low( But Variable) , head is high VFD can be planned  
4 Pump efficiency deterioration Flow is low, Head is low Wear ring clearance increase. Need to replace wear ring
5 Pump efficiency deterioration Flow is low, Head is low Pitting and wear of impeller and casing Surface coating can be done.
Table C

Pumping system operating efficient operation can be achieved by identification and elimination of reason for efficiency drop. Operate pumping system efficiently to reduce power consumption and save on operating cost.

For understanding pump coating to further improve efficiency, Please click here

Sample Pump curve

Sample pump Curve
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