This document discusses how to optimize energy usage in pumps through condition monitoring techniques. Pumps use 25% of the world's motor-driven electricity, or around 6.5% of global electricity production. Condition monitoring can detect degradation in bearings, casing wear, misalignment, and internal wear in impellers and seals. Performance analysis by measuring head-flow curves is particularly useful for detecting internal wear and optimizing the timing of pump overhauls to balance repair costs and wasted energy. The document provides examples of using performance analysis on boiler feed pumps to schedule optimal overhaul times that minimize total costs.

1. How to reduce the energy used
by your pumps
Ray Beebe
Speaker, trainer, author,
including:
Predicting maintenance of
pump using condition
monitoring
(Elsevier, 2004)

2. Pumps
World’s most
common machine
(after motors)
Use 25% of world’s
total motor-driven
electricity,
….or about 6.5% of
global electricity
production!!

3. C o n d itio n m o n ito rin g te ch n iq u e s
V ib ra tio n a n a lysis (ro ta tin g m a ch in e s)
P e rfo rm a n ce a n a lysis
A n a lysis o f we a r p a rticle s a n d co n ta m in a n ts
V isu a l in sp e ctio n /N D T
E le ctrica l p la n t te sts
….for pumps:
Bearing degradation - Oil sampling & analysis, vibration
analysis
Casing wear? - NDT
Misalignment? - Vibration
Internal wear, impeller and seals? - Performance analysis

4. Optimise energy
usage – good for
business AND
greenhouse effect.
Choose the best mix of
techniques to detect and
monitor the modes of
degradation you expect.

5. Pump internal wear
•Erosion of
impeller
Increased clearance
allows recirculation
•Erosion at
sealing/ wearing
rings

7. Pump internal wear
Ring section
diffuser pump
Sealing
rings
Internal
leakage

8. Pump internal wear
Internal leakage
recirculation
Head
H
H-Q with wear
Flow Q

9. Pump internal wear
Increasing internal
leakage reduces
Head at chosen
datum flow
% Reduction in head
Head reduction @ datum flow
shows cooling water pump
degradation (230kW)
20
15
10
5
0
0
500
1000
Days in service
1500

10. Close to linear for 4500kW pump, too
Boiler Feed Pump wear trend
% reduction in Head @ datum
flow
2
0
-2 0
1
2
3
4
5
6
7
8
9
-4
-6
-8
-10
y = -0.155x2 + 0.4907x - 0.1388
-12
Time: years since overhaul
10

11. § Effect of increased internal wear in
centrifugal pumps relates to Specific
Speed:
§ Using data at Best Efficiency Point:
N = Rotation speed, r/min
Q = flow per impeller eye, m³/h
H = head per stage, m
(Number resulting is close to that you get
if US units are used)
Ns
N
H
Q
0 . 75

13. 20
Clearances worn to
2X design
18
16
14
12
% Increase in
10
power
8
Clearances worn to
1.5X design
6
4
2
0
0
1000
2000
3000
Specific Speed (US units)
4000
5000

14. 1 Head-Flow method for CM
§ At around normal duty point is enough.
§ Checks condition of pump AND its system.
§ Repeatable pressure and flow measurement
needed, and speed for variable speed pumps.

15. •Plant DCS etc may work for
monitoring: e.g. boiler feed
pump operating H-Q point

16. DCS use off-line: historian
§ Boiler Feed
Pump

17. Pressure measurement

18. Pressure
measurement:
quick connect
couplings for
non-hazardous
liquids

19. Flow
measurement:
orifice plate
Repeatability can be OK
even if very short straight
upstream pipe length!

20. Annubar™ and similar

21. Expedient flow
measurement:
ultrasonic
flowmeter
(Several types)
[Note: pipe bore
diameter must be
known. If test flow
seems unusual, check
pipe wall thickness for
presence of buildup in
bore]

22. Flow measurement:
tank in system:
measure level
change with time.

23. 2 Shut-off Head
§ Simple test
§ Not always allowable: high energy pumps can
explode if dead-headed too long
§ Note that pumps with a rising head-flow curve
shape can give a greater shutoff head when worn!

24. Waste water pump, 19kW, Specific Speed 930

25. 3 Measurement of thrust
Annular clearance
balance leakoff flow
wears: thrust
balance flow
increases,
……therefore
likely that
clearances up at
the impellers,
too.

26. •Thrust balance flow
line is small
diameter; low cost
permanent flow
monitor possible.
•High temp
ultrasonic flow
sensors available

27. Boiler feed pump, variable speed (flow is proportional
to speed, therefore was corrected to datum speed).
This corresponds to
250kW wasted !
PLUS any
impeller sealing
leakage!

28. 4 Thermometric method
§ Assumes inefficiency shows as increase in
liquid temperature through pump
§ Well established in UK etc. water industry
l Special tapping points, 2D from suction,
discharge flanges (temp, pressure)
l Power measured: motor efficiency found
l Flow can be calculated
l Proprietary systems available

29. Thermodynamic process: use liquid properties
(water/steam: www.pepse.com)
3
2: P2 T2
Enthalpy
1: P1 T1
Entropy

30. § or use Whillier equation: for water up to 54 degC
(Units: degC, kPa, K)
100
[1 0 . 003 ( Inlet temp
2)
4160
Temp rise
Total Head
]

31. Yatesmeter, also Robertson’s kit…

32. Pressure, temperature
transducers at suction and
discharge, away from
pump flanges
Precision
power meter
Notebook takes data,
calculates flow, efficiency

33. Thermometric tests on boiler feed
pump with pipe surface temperature
•Usable results, BUT
must allow time for outlet
metal temp to stabilise.

34. Optimum time for overhaul - on
energy saving basis (1)
§ 1 Pump wear causes
drop in plant
production
• Overhaul readily
justified
§ 2 Pump duty is
intermittent to meet
demand
• Wear means
extra service time
and extra energy

35. Optimum time for overhaul - on
energy saving basis (2)
§ 3 Pump wear does
not affect plant
production, at least
initially.
Constant speed,
output controlled by
throttling – monitor
control valve position
§ 4 Pump wear does
not affect plant
production, at least
initially.
Output controlled
by varying speed –
monitor pump speed
•Same basic method applies...

36. An example:
§ Overhaul would cost $50 000.
§ Cost of power 10c/kWh.
§ Pump runs for 27% of time on average
§ Test at 24 months since last overhaul

38. § Motor efficiency is 90%, so the extra
power consumed by motor/pump combined
(WORN) is:
2300 – 2150 = 150kW ÷ motor efficiency
= 167kW

39. § Calculate the current extra cost of
electricity: (720h is average month):
167 × 0.10 × 0.27 × 720
kW
$
= $3240/month
%
h

40. § Calculate the average cost rate of
deterioration:
$ 3240 ÷ 24
= $ 135 /month/month.
Can now find the optimum time for
overhaul:
T
2O
C
= 27.2 months

41. Total cost
curve often
fairly flat
around the
optimum

42. Variable speed pump (1)

43. Variable speed pump (2)
• Same method as before used, but
with speed change.
Here, 31% increase in power to
maintain constant system flow, as
speed increases from 1490 to
1660 r/min

44. The method does not apply to all
pumps…..
§Small pumps may cost more to test than
overhaul, and energy costs may be just too
small to justify work
§Pumps of Specific Speed above about
2000 (r/min, m3/h, m or US units) have a
flat or declining Power-Flow curve, and
increased leakage does not use more power

45. Is the pump always at fault?

46. Maybe the system has changed?

47. Note that a lower system resistance is also possible

48. Is the rotation correct?
(DC motor drive)

49. Conclusion
§ Condition monitoring is much more than
vibration analysis
§ Performance analysis adds the energysaving dimension - USE IT !

50. Happy Monitoring !
raybeebemcm@gmail.com
[Co-ordinator for 16 years of
Monash University’s postgrad
programs in maintenance and
reliability engineering: off campus
learning (open to all: conditions
apply).
From Jan 2014, programs owned and
run by Federation University
Australia]