Transcript Thermodynamics I

Standard conduit designations
Steel pipe
 Ductile iron pipe
 Steel tubing
 Copper tubing
 Polymeric conduits
 Reinforced hoses
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Gear pump
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Fixed displacement
V = (/4) (Do2 – Di2) L
Volumetric efficiency ~ 80 to 90%
Theoretical flow rate Q = VN/231
Least expensive
Lowest level of performance; slippage due to
gear wear
Mobile equipment; machine tools
Vane pump
Can be variable displacement pump
 Volumetric efficiency – 82 to 92%
 Intermediate in costs & performance
 Needs clean oil to control wear
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Piston pump
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Axial pump
Bent axis pump
Fixed or variable displacement
Swash plate
Volumetric efficiency – 90 to 98%
Most expensive
Highest level of performance: highest pressures
Good durability & reliability
PUMP
TYPE
PRESSU
RE
RATING
(PSI)
SPEED
RATING
(RPM)
OVERALL
EFFICIENCY
(%)
HP/LB
FLOW
CAPACITY
(GPM)
COST
($/HP)
External
Gear
2000 –
3000
1200 –
2500
80 – 90
2
1 – 150
4–8
Internal
Gear
500 –
2000
1200 –
2500
70 – 85
2
1 – 200
4–8
1000 –
2000
1200 –
1800
80 – 95
2
1 – 80
6 – 30
Axial
Piston
2000 –
12000
1200 –
3000
90 – 98
4
1 – 200
6 – 50
Radial
Piston
3000 12000
1200 1800
85 – 95
3
1 - 200
5 - 35
Vane
Pump selection
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Depends on the following:
Flow rate
Operating speed
Pressure rating
Performance – efficiency
Reliability
Costs
Pump selection:
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Determine nature of load & task
Decide on actuator to accomplish task
Calculate the flow rate of pressurized fluid to
move load through distance at given time limit
Select pressure: P=F/A
Set pump and prime mover speeds
Select pump type
Consider any special needs
Energy Conversions
Fv
cylinder
VI
T
Electric
Motor
pQ
Hydraulic
Pump
Hydraulic
Cylinder
or
Motor
External
Load
T
Motor
1.
Piston
2.
Cushion nose
3.
Cylinder cap
4.
Stroke volume
5.
Cushion orifice
6.
Throttle
7.
Cushion adjustment screw
8.
Mother
9.
Non-return valve
10. Gas valve