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PUMPING 101 – TASK 3

PUMPING 101 – TASK 3. NPSH AND PUMP CURVE REVIEW. PUMPING 101 – TASK 3. NPSH. Why Worry About NPSH ?. Pumps Don’t Suck. Remember Pump Basics. The fluid needs to enter the impeller before the impeller can begin adding energy.

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PUMPING 101 – TASK 3

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  1. PUMPING 101 – TASK 3 NPSH AND PUMP CURVE REVIEW

  2. PUMPING 101 – TASK 3 NPSH

  3. Why Worry About NPSH ? Pumps Don’t Suck.

  4. Remember Pump Basics The fluid needs to enter the impeller before the impeller can begin adding energy. NPSH defines the energy available to the fluid above it’s vapor pressure. • Suction pressure • Pressure line • Atmospheric pressure • Pump inlet • Evaporation pressure • Pump discharge • Vacuum • NPSH • NPSHR

  5. Absolute Pressure What is difference between PSI, PSIA and PSIG? PSI is a unit of measurement. PSIG is Gauge pressure, and is relative to atmospheric pressure (reads 0 psi on the bench). PSIA is Absolute pressure, and includes atmospheric pressure (reads about 14.7 psi on the bench at sea level).

  6. Two “Types” of NPSH NPSHRis the NPSH requiredby the pump. It is a function of the pump design. (This is the NPSH shown on the pump curve.) NPSHA is the NPSH availableby the pump. It is a function of the system design. NPSH Curve

  7. NPSH is Like a Checkbook NPSHR is like the money needed to pay your bills NPSHA is income. You need much more income than bills!

  8. The “Rule”: For practical purposes, forget the equal sign: NPSH Availablemust be GREATER than the NPSH Required. NPSHA NPSHR ≥

  9. Take This Note!!! Add minimum 2 foot safety factor to NPSHR!

  10. NPSHR Chief factors influencing NPSHR include. impeller eye area vane inlet design the relationship with the casing. NPSHR is determined by factory testing.

  11. NPSHA The NPSHA is influenced by several factors, many of which are controllable or modifiable. These factors include: Absolute pressure Vapor pressure Suction pressure Friction loses Highly aerated water (as seen in cooling towers)

  12. NPSHA Formula NPSHA = HA ± HS - HVPA - HF Where: HA= Absolute pressure HS= Suction pressure (head) HVPA = Vapor pressure HF = suction piping Friction head

  13. NPSHA and Suction Conditions In Suction Lift Example B, HS is a Negative Number A.FloodedSuction B.Suction Lift NPSH = HA + HS – HVP - HF NPSHA = HA - HS – HVP - HF

  14. PUMPING 101 – TASK 3 PUMP CURVE REVIEW

  15. Atmospheric Pressure 1 PSI = 2.31ft. H20 @ 70°F = 2.0438inches of mercury (hg) 14.7 PSI = 33.9ft. H20 @ 70°F = 30inches of mercury (hg) Watch the weather report!

  16. Atmospheric Pressure vs. Altitude

  17. Vapor Pressure of Water Properties of Water at Various Temperatures

  18. Vapor Pressure Curve Gas Critical Point Liquid Vapor Pressure Liquid and Vapor Gas Vapor Temperature

  19. Catalog Pump Curves What are the significant data points on this pump curve? Power Efficiency Flow & Head NPSHr

  20. Catalog Pump Curves 26 hp Power Efficiency 88% Flow 1300 gpmHead 70 ft NPSHr 10 ft

  21. www.grundfos.com

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