pressure: troubleshooting problem pump installationsc.ymcdn.com/sites/ · · 2018-01-08pressure:...

© 2017 HDR, Inc., all rights reserved.

Performance Under Pressure: Troubleshooting Problem Pump InstallationsBrian Thorsvold, PE

01 Introduction/Purpose

02 Centrifugal Pump Basics

03 Pump Testing Basics

04 Problem Pump Case Studies

Agenda

Certified pump testing Start-up / field testing Testing for preventative maintenance Optimizing operational efficiency Maximize operational life Find problems before damage occurs

Why Test?

System Head Curve

Static head Pressure Head Total Head Flowrate

Typical Centrifugal Pump Curve

Filters 1 – 18 in operation Filter pump 2 on at 24 MGD Filter pump 5 on at 24 MGD Total flow = 48 MGD Water surface elevation =

541.85 ft.

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iency

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Head

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H (ft

)Flow (gpm)

Pump Head (ft) System Head Hi (ft) Efficiency (%)NPSHR (ft) NPSH3 (ft) NPSHA (ft)

PRESSURE HEAD

STATIC HEAD

Low WetwellLevel

System Head Curve

Static head Pressure Head Total Head Flowrate


Filters 1 – 18 in operation Filter pump 2 on at 24 MGD Filter pump 5 on at 24 MGD Total flow = 48 MGD Water surface elevation =

541.85 ft.

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iency

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H (ft

)Flow (gpm)

Pump Head (ft) System Head Hi (ft) System Head Lo (ft) Efficiency (%)NPSHR (ft) NPSH3 (ft) NPSHA (ft)

High Wetwell Level

PRESSURE HEAD

STATIC HEAD

Pump Head-Capacity Curve

Pump operating point


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iency

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Pump Head (ft) System Head Hi (ft) System Head Lo (ft)Efficiency (%) NPSHR (ft) NPSH3 (ft)NPSHA (ft)

Efficiency Curve

Best Efficiency Point (BEP)


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BEP – best efficiency pointo The point on the pump curve where efficiency is greatest.

POR – preferred operating rangeo The range where the pump will satisfactorily operate without vibrations above standards or

damageo Varies depending on pump size, typically between 70% to 115% of the flow rate at BEP

AOR – allowable operating rangeo The range where the pump will operate satisfactorily but will experience some cavitation,

vibration above standards and shorter service life. The pump manufacturer will determine this range

o Generally in the flow rate range is 60%-120% of the flowrate at BEP Obtain these values from pump manufacturer for specific pumps being

considered

Defined Terms

Best Efficiency Point (BEP)

Preferred Operating Range

Acceptable Operating Range

Pump Operating Ranges

Filters 1 – 18 in operation Filter pump 2 on at 24 MGD Filter pump 5 on at 24 MGD Total flow = 48 MGD Water surface elevation = 541.85

ft.

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Effic

iency

(%)

Head

, NPS

H (ft

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Flow (gpm)Pump Head (ft) System Head Hi (ft) System Head Lo (ft) Efficiency (%)NPSHR (ft) NPSH3 (ft) NPSHA (ft)

ACCEPTABLE OPERATING RANGE

PREFERREDOPERATING RANGE

LEFT OF BEP: High shaft deflection Vibration Temperature Build-up Excess recirculation Very inefficient

Operating Outside the Acceptable Range

LEFT OF BEP: High shaft deflection Vibration Temperature Build-up Excess recirculation Very inefficientRIGHT OF BEP: Cavitation High flow – high velocity – high wear Motor overload

Operating Outside the Acceptable Range

Damage Caused by Cavitation / Vibration

Variable Speed Pumping Flow function of speed Head function of square of

the speed



ft.

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H (ft

)Flow (gpm)


Variable Speed Pumping Check operating condition

at min. speed also



ft.

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Effic

iency

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H (ft

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Flow (gpm)Pump Head (ft) System Head Hi (ft) System Head Lo (ft) Efficiency (%)

NPSHR (ft) NPSH3 (ft) NPSHA (ft)

System curve Acceptable operating range Variable speed pumping curves Efficiency curves

Typical Variable Speed Pump Curve

Pump speed (rpm) Discharge pressure (psi/ft) Flowrate (gpm) Power (HP) Correct to gage elevation

Certified Pump Testing

Design Criteria

Designed to pump 5,000 – 8,000 gpm [6 – 10 gpm/SF filter backwash rate] Pump suction El. is 2’ higher than

discharge El. Variable speed

Case Study No. 1Filter Backwash Pump Testing

Backwash piping configurationFilter Backwash Pump Testing

Submittal Curve

Filter Backwash Pump Testing

Initial Test Results: 7,550 gpm max (vs. 8,000 gpm required) Pump head? Pump speed?

Filter Backwash Pump TestingInitial Manufacturer Diagnosis: Air trapped in piping increasing head Piping change during construction added

head

Field Testing

Pressure gage Manometer Tachometer Ladder


Field Testing

Initial Test ResultsFilter Backwash Pump Testing


ft.

Backwash Supply Pump TestingTest Flowrate Pressure Gage Manometer Depth to Water Vel Head Corrected Gage Pressure Corrected HeadNumber (gpm) (PSI) (in H2O)1 (inches)1 (feet) (feet)2,3 (feet)3

1 3270 4.25 out of range 82 0.26 22.0 22.22 4140 3.1 out of range 82.5 0.42 19.4 19.83 4840 2.25 out of range 83 0.58 17.4 18.04 5480 1.65 137 83 0.74 18.3 19.15 6090 1.0 116 83 0.92 16.6 17.56 6520 0.5 102 83 1.05 15.4 16.57 6970 0.1 92 83 1.20 14.6 15.88 7550 0 62 84 1.41 12.2 13.6

1 All measurements use TOC (El. 544.50) as zero basis, (WSE approx 537.58)2 Gage height was 64" above TOC (El. 549.83)3 When both gage pressure and manometer height is available, manometer reading is used as assumed to be more accurate

Pump Test No. 1


Certified Curve

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Dyn

amic

Head

(ft)

Flowrate (gpm)

Pressure Gage

Manometer

Certified Curve

Pump Test No. 2


Certified Curve

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amic

Head

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Flowrate (gpm)

Retest Results

Certified Curve

Backwash Piping ConfigurationFilter Backwash Pump Testing

Pump Test No. 3


Certified Curve

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Head

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Flowrate (gpm)

103% speed

Certified Curve

Results Corrected pump

operation Overclocked pump

to achieve required flow in last filter

Design Criteria

Mag drive centrifugal hypochlorite pump 50 gpm @ 14 ft TDH 3-inch suction line, 3-inch discharge

Case Study No. 2Chemical Recirculation Pump

Damaged Components Broken sleeve bearing Damaged thrust washer Outer magnet assembly after exposed to fluid

Case Study No. 2Chemical Recirculation Pump

System Curve Review

Chemical Recirculation Pump Testing

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Dyn

amic

Head

(ft)

Flowrate (gpm)

Full Tank

Empty TankSystemCurve

System Curve Review


-5

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Flowrate (gpm)

2-inch

3-inch

SystemCurve

Results


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Flowrate (gpm)

2-inch

3-inch

SystemCurve

3-inch discharge pipe supposed to be 2-inch

Pump runout / cavitation

Pump failure after 2 months operation

Throttle pump back on curve

Background / Review

Four 1,000 HP pumps (identical) One pump with lower outputo 6,900 gpm (each of 3 pumps)o 6,100 gpm (1 pump)

Case Study No. 3High Service Pump performance

Design Criteria


D

Pressure Gage

Control Valve

Results

800 gpm more 25 psi less pressure Assume 2,000 hrs/yr Saves ~ $36,000/yr in electrical cost


Results and Conclusions

Factory testing to confirm pump meets design intent

Start-up testing to establish proper operation in system

Routine testing/checking to track operational performance

Pump Testing

Questions?Brian [email protected]

pressure: troubleshooting problem pump installationsc.ymcdn.com/sites/ · · 2018-01-08pressure:...

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