螺杆泵简介

At what viscosity is a PD pump more cost efficient ?
95.0% 90.0%
Efficiency
85.0% 80.0% 75.0%
Centrifugal
Rotary Screw
70.0% 65.0% 60.0% 55.0% 50.0% 1.8 cSt 20 cSt 43 cSt 108 cSt 216 cSt 350 cSt
Unlike kinetic energy pumps they do not create pressure ! They overcome resistance!
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The Fundamental Operating Principle of Positive Displacement pumps
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HISTORY
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Archimedes invents the Screw pump Ctesibus invents the reciprocating pump
230 BC 200 BC
Ramelli invents the Vane Pump
Serviere invents Gear Pump Denis Papin invents Centrifugal Pump
PD Pumps When do you use them?
By Mark Korzec
PUMPS
A METHOD OF MOVING A FLUID
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Trends in the Marketplace
The changing nature of fluids handled:
1. Higher Viscosities Fluids 2. Lower Viscosity Fluids 3. Mixed Phases of Fluids
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Less efficient
Viscosity
operation
Inability to pump
Optimum Performance
Impeller Vane Angle
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Turbulent vs. Laminar Flow
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Centrifugal Pump Efficiency Rules of Thumb
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Centrifugal Pumps and Best Efficiency Point (BEP)
1932
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Why is it that the 1689 invention by Denis Papin did not have a significant impact on the world for nearly 225 years?
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Prior to 1920 the vast majority of pumps were positive displacement predominantly reciprocating pumps
1580
1593 1689
Revillion invents the Screw Chamber Wheel
Quimby invents the 2 Screw Pump Montelius invents the 3 Screw pump
1830
1894 1924
Moineau invents the Progressive Cavity Pump
RELEASE VOLUME AGAINST DISCHARGE PRESSURE
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POSITIVE DISPLACEMENT PUMPS DON’T CRREATE PRESSURE THET OVERCOME RESISTANCE
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POSITIVE DISPLACEMENT PUMP
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Slip
Low pressure end
High pressure end
Rotor Displacement
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SLIP
CLEARANCE
VISCOSITY PRESSURE
WARREN PUMPS INC.
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Pump Flow Performance
F L O W
DISPLACEMENT
Viscosity 21 cst 54 cst 108 cst 162 cst 216 cst
Flow 3% Reduction Head 2% Reduction Power Increase 10%
8% 5% 20%
14% 11% 30%
19% 14% 50%
23% 18% 65%
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What is different about Positive Displacement Pumps ?
Understanding the operating concept of Pumps can provide you with the necessary information to make an appropriate decision.
It allows you to rely on your knowledge instead of solely on a pump supplier.
Viscosity of the fluid
Temperature of the fluid Flow required Discharge Pressure required Suction Condition (NPSHA)
Specictive
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SIMPLE EXAMPLE IN PUMPING A FLUID
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One way to view this
What happens to flow at 1 RPM?
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Another way to view this
What happens at high speed?
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World dominated by two fluids water and oil
PC Twin Screw
Three Screw
Recip Vane
hose Gear Pumps
World of Centrifugal Pumps
Lobe
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Criteria needed in order to determine a pump technology… Fluid characteristic
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Reciprocating
Positive Displacement Pumps
A need to move a fluid
A pump is the best way to move the fluid
Centrifugal Pumps
Rotary
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Piston
Reciprocating
Plunger
Cost Savings
Viscosity
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Centrifugal Pumps and Best Efficiency Point (BEP)
BEP
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Centrifugal Pumps and Best Efficiency Point (BEP)
In the real world what happens is generally not on the data sheets Was the rated pressure increased by the fluid engineer to in safe? How accurate is the rated viscosity? Will the system curve change significantly when a factor such as viscosity and pressure change? What happens to BEP when any of these change?
Gear Rotary
Screw
Progressive Cavity Twin Screw Multiple screw
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My World of Fluids
Light Viscosities Liquids Water Oil Hot Fluids
Liquid with Solids
Slurries High Viscosity Fluids Liquids with Gas Gases
S L I P
PRESSURE
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Performance Curves
Pressure
Positive Displacement Pump with a variable speed drive constant capacity against varying pressure Capacity
All of these present challenges for pumps !
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How we move fluids
•Centrifugal Pumps
•Gear Pumps •Other Positive Displacement Pumps
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Challenges for centrifugal pumps may be Opportunities for positive displacement pumps 1. The power required to move more viscous fluids 2. The NPSH challenges with low viscosity (low vapor pressure) fluids 3. The NPSH challenges with High Viscosity fluids 4. The challenge with Gas in fluid streams 5. The Shear sensitivity of Fluids 6. Varying pressures in the process
Centrifugal Pump
Capacity
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Performance Curves
Centrifugal Pump
Positive Displacement Pump
Pressure
Performance Variation is Negligible
Capacity
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Efficiency and Energy savings
Diaphragm Flexible Hose Flexible Liner Positive Displacement Pumps Flexible Vane
Flexible member
External Gear Lobe Internal Gear Blade Roller Vane Slipper
The typical engineer 100 years ago was familiar with Positive displacement technology… It was the pump of choice
Now Centrifugal pump technology dominates our world … and for a logical reason!
CENTRIFUGAL PUMP
0
0
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The Fundamental Operating Principle of Centrifugal pumps
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Airfoil – Angle of attack
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Lift
Stall
Optimum Performance Airfoil Angle
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Centrifugal Pump
Performance Curves
Performance Variation
Positive Displacement Pump
System Head Curve
Pressure
Example: to increase 3 meters head (.33 bar), capacity would decrease by 28%.
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CENTRIFUGAL PUMPS
ADD VELOCITY
CONVERT VELOCITY TO PRESSURE
WARREN PUMPS INC.
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DISPLACEMENT
POSITIVE
PUMPS
ENCLOSE A VOLUME AT SUCTION DISPLACE THE VOLUME TO DISCHARGE