1. CENTRIFUGAL PUMP TROUBLESHOOTING

2. PUMP PROBLEM AREAS SEALS BEARINGS NOISE & VIBRATION LACK OF FLOW
LACK OF HEAD
BROKEN SHAFTS
OVERLOADED MOTOR
ETC.
THESE ARE ONLY A FEW OF THE MANY AREAS THAT CAN BECOME A PROBLEM

3. CAUSES OF PUMP PROBLEMS
PUMP INCORRECTLY SIZED
MISALIGNMENT
CAVITATION
PIPING DESIGN
LUBRICATION
FOUNDATION
ETC
THESE ARE ONLY A FEW OF THE MANY CAUSES OF CENTRIFUGAL PUMP PROBLEMS
A “TROUBLESHOOTING GUIDE” IS AVAILABLE IN THE IOM.
I HAVE RE-MADE THAT GUIDE IN A DIFFERENT FORMAT. IT IS INCLUDED AT THE END OF THIS PRESENTATION.

4. FOCUS ON MATCHING THE PUMP & SYSTEM
FIND OUT WHERE THE PUMP IS OPERATING ON THE CURVE
OFTEN THE PUMP WILL OPERATE WITH FEWER PROBLEMS BY OPERATION CLOSER TO THE BEP (BEST EFFICIENCY POINT)
WE’LL LOOK AT THE COMMON PROBLEM OF A CAVITATING PUMP
THE FOCUS OF MY TROUBLESHOOTING PRESENTATION WILL BE ON GETTING THE PUMP AND SYSTEM TO MATCH
THERE ARE NO “ONE SIZE FITS ALL” SOLUTIONS TO ANY PROBLEM.
ALL SOLUTIONS WILL DEPEND ON THE PARTICULAR PUMP AND SYSTEM.
LATER WE WILL LOOK AT AN EXAMPLE OF A CAVITATING PUMP AND WAYS TO CHANGE THE SYSTEM CURVE OR WHERE WE ARE OPERATING ON THAT CURVE.

5. NOTE LOCATION OF THE BEP (BEST EFFICIENCY POINT)
THIS IS WHERE THE RADIAL LOADS ARE AT THEIR MINIMUM
THIS IS WHERE THE FLOWS ENTERING THE IMPELLER BEST MATCH THE VANES
THIS IS WHERE THE FLOWS ENTERING THE THROAT & DIFFUSER BEST MATCH THE CASING CUTWATER
VIBRATION IS AT A MINIMUM
NOTE THE MRF (MINIMUM RECOMMENDED FLOW) LINE
NOTE THE NPSHR LINE. THE HIGHER THE FLOW THE HIGHER THE NPSHR. NPSHR INCREASES RAPIDLY TO THE RIGHT OF BEP. CAVITATION PROBLEMS INCREASE RAPIDLY TO THE RIGHT OF BEP AS A RESULT.
POWER IS AT MAXIMUM AT THE END OF THE CURVE

6. THE SYSTEM CURVE SHOWN IN GREEN REPRESENTS A TYPICAL SYSTEM
NOTE THE 30 FOOT STATIC HEAD (AT ZERO FLOW)
EVERYTHING ABOVE THE 30 FOOT STATIC HEAD LINE IS THE FRICTION COMPONENT OF THE SYSTEM HEAD CURVE.
THE PUMP WILL OPERATE WHERE THE PUMP CURVE AND THE SYSTEM HEAD CURVE MEET

7. WHY IS THE SYSTEM CURVE IMPORTANT ?
SYSTEM CURVE IS FUNDAMENTAL TO EVERYTHING THE PUMP DOES
CRITICAL TO UNDERSTAND THE STATIC AND FRICTION COMPONENTS OF THE SYSTEM CURVE
FOR OPTIMIZING – WE ASK IF WE CAN CHANGE THE SYSTEM CURVE OR WHERE WE ARE OPERATING ON IT

8. PUMP AND SYSTEM PUMP DOES NOT CONTROL THE SYSTEM
THE SYSTEM CONTROLS THE PUMP
THE PUMP SIMPLY REACTS TO WHAT THE SYSTEM TELLS IT TO DO
THERE IS NO LIMIT TO THE POSSIBLE SYSTEM CONFIGURATIONS

9. NOTE THE THREE SYSTEM HEAD CURVES. EACH HAS A 30 FOOT STATIC HEAD
NOTE THE THREE SYSTEM HEAD CURVES. EACH HAS A 30 FOOT STATIC HEAD. EACH HAS A DIFFERENT FRICTION COMPONENT.
NOTE THE LEFT SYSTEM HEAD CURVE WILL MAKE THE PUMP OPERATE BELOW THE MINIMUM RECOMMENDED FLOW. CONSIDER THE POSSIBLE PROBLEMS WITH INCREASED DEFLECTION, AND VIBRATION WHAT ABOUT POSSIBLE OVERHEATING?
THE SYSTEM CURVE ON THE RIGHT IS SUBJECT TO CAVITATION, VIBRATION AND DEFLECTION. WHAT ABOUT A MOTOR THAT IS NOT SIZED TO COVER THE END OF THE CURVE?

10. THIS SHOWS TWO SYSTEM HEAD CURVES WITH DIFFERENT STATIC HEADS.
ONE CURVE HAS ALMOST NO FRICTION HEAD
ONE CURVE HAS NO STATIC HEAD
THIS PUMP WILL REACT VERY DIFFERENTLY IN THESE TWO SYSTEMS IF MINOR CHANGES ARE MADE TO THE RPM OR IMPELLER DIAMETER.

11. DEVELOP SYSTEM CURVE FROM FIELD MEASUREMENTS
CAPTURE CRITICAL ELEMENTS OF THE SYSTEM
HOW?
REVIEW PI&D AND PIPING ISOMETRICS
TALK TO OPERATORS
WALK DOWN THE SYSTEM & RECORD ALL COMPONENTS
CALCULATE TDH (STATIC & FRICTION)
A LOT OF TEDIUS WORK. IT’S EASY TO MISS SOMETHING.
WE ALSO HAVE A PUMP INSTALLED IN A SYSTEM AND CAN TAKE SOME PRESSURE MEASUREMENTS TO DETERMINE THE SYSTEM CURVE

12. CONSIDER THIS SYSTEM AS AN EXAMPLE:
TRANSFERING WATER FROM ONE TANK TO ANOTHER
FROM THE PUMP INSTALLED IN A SYSTEM WE CAN LEARN A LOT ABOUT THE SYSTEM CURVE. REMEMBER THAT THE PUMP CURVE AND THE SYSTEM CURVE HAVE A COMMON POINT AT THE PUMP’S OPERATING POINT.
WE NEED THE TWO COMPONENTS OF THE SYSTEM CURVE:
SYSTEM STATIC HEAD
SYSTEM FRICTION HEAD
WE ALSO NEED A FLOW MEASUREMENT FROM THE “SYSTEM” OR A PUMP CURVE TO ESTIMATE THE FLOW

13. SYSTEM STATIC HEAD
STATIC HEAD IS THE TOTAL OF THE ELEVATION AND PRESSURE COMPONENTS
HSTATIC= (2.31/SG) X (P5-P1) + Δ ELEVATION
HSTATIC= (10.2/SG) X (P5-P1) + Δ ELEVATION
(metric constant)
(PRESSURE COMPONENT IS ZERO IF THE TANK IS OPEN TO THE ATMOSPHERE)
ESTIMATE THE ELEVATION DIFFERENCE FROM DRAWINGS, DIRECT MEASUREMENTS, PRESSURE REASINGS, ETC.
DETERMINE THE PRESSURE COMPONENT FROM PRESSURE READINGS, TALK TO OPERATORS
REMEMBER THAT IF A TANK IS OPEN TO THE ATMOSPHERE, THE GAGE PRESSURE IS ZERO
SG = SPECIFIC GRAVITY
P1 & P2 ARE IN PSI

14. CONSIDER THIS SYSTEM AS AN EXAMPLE:
TRANSFERING WATER FROM ONE TANK TO ANOTHER
FROM THE PUMP INSTALLED IN A SYSTEM WE CAN LEARN A LOT ABOUT THE SYSTEM CURVE. REMEMBER THAT THE PUMP CURVE AND THE SYSTEM CURVE HAVE A COMMON POINT AT THE PUMP’S OPERATING POINT.
WE NEED THE TWO COMPONENTS OF THE SYSTEM CURVE:
SYSTEM STATIC HEAD
SYSTEM FRICTION HEAD
WE ALSO NEED A FLOW MEASUREMENT FROM THE “SYSTEM” OR A PUMP CURVE TO ESTIMATE THE FLOW

15. SYSTEM FRICTION HEAD HTOTAL = HSTATIC + HFRICTION
HFRICTION = HTOTAL – HSTATIC
WE CAN MEASURE THE PUMP’S TOTAL HEAD FROM P2 AND P3
HTOTAL = (2.31/SG) X (P3 – P2)
(use 10.2 as constant for metric calculation)
REMEMBER TO ADD VELOCITY HEAD IF THE PIPE SIZE AT P3 & P2 LOCATIONS ARE A DIFFERENT SIZE
ADD ANY GAGE ELEVATION CORRECTION TO READINGS

16. SYSTEM CURVE WE HAVE TWO POINTS ON THE SYSTEM HEAD CURVE
FILL IN THE COMPLETE CURVE WITH THE FOLLOWING RELATIONSHIPS:
K=(HTOT1-HTOT2)/(Q12-Q22) = SYSTEM LOSS COEFFICIENT
HFRICTION = K X Q2
HTOTAL = HSTATIC + HFRICTION

17. Now that we have an accurate system curve we can decide what changes are possible or necessary to help solve the “problem”.

18. WAYS TO REDUCE FLOW CUT DOWN IMPELLER DIAMETER DECREASE PUMP SPEED
THROTTLE WITH DISCHARGE VALVE
THROTTLE WITH ORIFICE IN DISCHARGE PIPE
INCREASE FRICTION LOSS IN DISCHARGE PIPE
NOTICE THAT THE FIRST TWO, BY THEMSELVES, WORK WITH THE EXISTING SYSTEM HEAD CURVE
THE REST CAN BE USED TO CHANGE THE SYSTEM TO ALLOW THE PUMP TO OPERATE ON A MORE FAVORABLE OPERATING POINT

19. WAYS TO INCREASE FLOW INCREASE IMPELLER DIAMETER INCREASE PUMP SPEED
REDUCE FRICTION LOSS
ADD RECIRCULATION LINE BACK TO SUCTION TANK
NOTICE THAT THE FIRST TWO, BY THEMSELVES, WORK WITH THE EXISTING SYSTEM HEAD CURVE
THE SECOND TWO CAN BE USED TO CHANGE THE SYSTEM TO ALLOW THE PUMP TO OPERATE ON A MORE FAVORABLE OPERATING POINT

20. ALTERNATIVE THREE GAGE METHOD
TOTAL SYSTEM HEAD CAN ALSO BE ESTIMATED IF THE P4 PRESSURE DOWNSTREAM OF THE MAIN THROTTLING VALVE IS AVAILABLE
P2 AND P3 IS ALSO NEEDED
NEED TO HAVE:
PUMP CURVE, PUMP SIZE, EXACT IMPELLER DIAMETER, THROTTLING VALVE, THREE PRESSURE GAGES

21. CONSIDER THIS SYSTEM AS AN EXAMPLE:
TRANSFERING WATER FROM ONE TANK TO ANOTHER
FROM THE PUMP INSTALLED IN A SYSTEM WE CAN LEARN A LOT ABOUT THE SYSTEM CURVE. REMEMBER THAT THE PUMP CURVE AND THE SYSTEM CURVE HAVE A COMMON POINT AT THE PUMP’S OPERATING POINT.
WE NEED THE TWO COMPONENTS OF THE SYSTEM CURVE:
SYSTEM STATIC HEAD
SYSTEM FRICTION HEAD
WE ALSO NEED A FLOW MEASUREMENT FROM THE “SYSTEM” OR A PUMP CURVE TO ESTIMATE THE FLOW

22. THREE GAGE METHOD DIFFERENCE BETWEEN P3 AND P2 IS THE PUMP’S TDH
DIFFERENCE BETWEEN P4 AND P2 IS THE SYSTEM TDH
ADD VELOCITY HEAD IF THE PIPE SIZE AT P3 & P2 LOCATIONS ARE A DIFFERENT SIZE
ADD VELOCITY HEAD IF THE PIPE SIZE AT P4 & P2 LOCATIONS ARE A DIFFERENT SIZE
ADD ANY GAGE ELEVATION CORRECTION TO ALL READINGS

23. THREE GAGE METHOD
RECORD READINGS WITH FULLY OPEN VALVE WITH PUMP CAVITATING
RECORD READINGS WITH VALVE THROTTLED SO THERE IS NO CAVITATION
DETERMINE THE PUMP TDH WHERE THE CAVITATION STOPS
DETERMINE THE SYSTEM TDH WHERE THE CAVITATION STOPS
USE THE PUMP CURVE AND THE PUMP TDH FROM STEP 3 TO DETERMINE THE FLOW WHERE THE CAVITATION STOPS
RESIZE THE PUMP/IMPELLER TO MATCH THE FLOW AND SYSTEM HEAD FROM STEP 5
ADD VELOCITY HEAD IF THE PIPE SIZE AT P3 & P2 LOCATIONS ARE A DIFFERENT SIZE
ADD VELOCITY HEAD IF THE PIPE SIZE AT P4 & P2 LOCATIONS ARE A DIFFERENT SIZE
ADD ANY GAGE ELEVATION CORRECTION TO ALL READINGS

24. GOTCHA’S
GAGE READINGS IN DIFFERENT SIZE PIPE AND FAILURE TO CONSIDER PIPE VELOCITY HEAD
FAILURE TO CONSIDER STATIC HEAD DIFFERENCE IN GAGE READINGS
CONSIDER WAYS TO KEEP YOURSELF OUT OF TROUBLE IN TAKING READINGS AND INTERPRETATION OF THE DATA
AN 8X10 PUMP AT 2000 GPM HAS A VELOCITY HEAD DIFFERENCE OF 1.5 FEET – NOT A BIG DEAL
A 1X2 PUMP AT 150 GPM HAS A VELOCITY HEAD DIFFERENCE OF 45 FEET - COULD BE SIGNIFICANT
CORRECT GAGE READINGS TO A COMMON ELEVATION – LIKE THE CENTERLINE OF THE PUMP

25. MORE GOTCHA’S PUMP HEAD CAPACITY CURVE DEVELOPED AT A DIFFERENT SPEED
INACCURATE PRESSURE GAGES
INACCURATE FLOW METERS
PUMP SPECIFIC CURVE NOT EQUAL TO GENERIC CURVE
IMPELLER, OTHER PARTS WORN
NO CURVE AVAILABLE / DON’T KNOW IMPELLER DIAMETER
ACTUAL VS RATED SPEED. PUBLISHED CURVE AT 1750 BUT PUMP IS RUNNING CLOSER TO 1800