Hydraulic Fluids Components and Symbols
Hydraulic Systems
Examples of hydraulic systems
Basic hydraulic system
Basic fluid power symbols
Basic fluid power ANSI/ISO symbols
Basic fluid power symbols
Hydraulic Pumps
Pump characteristic
Operating pressure
Speeds
Displacement volume (V) – volume of liquid per revolution Volumetric flow rate: Q = n × V where n : number of rotation (rpm)
V : displacement volume (per rev)
Pump Efficiency (Volumetric)
To determine performance of pump
Divided into two:
Volumetric efficiency (ηvol) : Indicates amount of leakage that takes place in the pump. Effected by pressure.
ηvol = QA/QT
= (actual flow rate)/(theoretical flow rate)
Pump Efficiency (Mechanical)
Mechanical efficiency (ηm): Indicates amount of energy losses due to reasons other than leakage. ηm = pQT/TAN
= (pump output power, no leakage)/(actual power delivered to pump) where p : pump discharge pressure [Pa]
QT: pump theoretical flow rate [m3/s]
TA : theoretical torque delivered to pump [Nm]
N : pump speed [rpm]
Pump Efficiency (Mechanical)
Or ηm = TT/TA
= (theoretical torque to operate pump)/(actual torque delivered to pump) where TT [Nm] = (V [m3] × P [Pa])/2π
TA = (actual power delivered to pump [W])/(2πN/60 [rpm])
Total/overall efficiency
Total efficiency: ηtot = ηvol × ηm
where
ηtot : total efficiency ηvol : volumetric efficiency ηm : mechanical/motor efficiency
Example (1)
A leakage of oil from a pump is 6% at 230 bar. Calculate the total efficiency if the flow rate at 0 bar is 10 dm3min-1 and the motor efficiency is 75%.
Solution:
Q (P = 0 bar) = 10 dm3min-1
Q (P = 230 bar) = 10 × 0.94 = 9.4 dm3min-1 ηmotor = 0.75, ηvol = 9.4/10 = 0.94
Therefore
ηtot = ηmotor × ηvol = 0.705 (= 70.5 %)
Example (2)
A pump has a displacement volume of 100 cm3. It delivers 0.0015 m3/s at 1000 rpm and 70 bars. The prime mover input torque is 120 Nm.
a) What is the overall efficiency of the pump?
b) What is the theoretical torque required to operate the pump?
Solution
Examples of hydraulic systems
Basic hydraulic system
Basic fluid power symbols
Basic fluid power ANSI/ISO symbols
Basic fluid power symbols
Hydraulic Pumps
Pump characteristic
Operating pressure
Speeds
Displacement volume (V) – volume of liquid per revolution Volumetric flow rate: Q = n × V where n : number of rotation (rpm)
V : displacement volume (per rev)
Pump Efficiency (Volumetric)
To determine performance of pump
Divided into two:
Volumetric efficiency (ηvol) : Indicates amount of leakage that takes place in the pump. Effected by pressure.
ηvol = QA/QT
= (actual flow rate)/(theoretical flow rate)
Pump Efficiency (Mechanical)
Mechanical efficiency (ηm): Indicates amount of energy losses due to reasons other than leakage. ηm = pQT/TAN
= (pump output power, no leakage)/(actual power delivered to pump) where p : pump discharge pressure [Pa]
QT: pump theoretical flow rate [m3/s]
TA : theoretical torque delivered to pump [Nm]
N : pump speed [rpm]
Pump Efficiency (Mechanical)
Or ηm = TT/TA
= (theoretical torque to operate pump)/(actual torque delivered to pump) where TT [Nm] = (V [m3] × P [Pa])/2π
TA = (actual power delivered to pump [W])/(2πN/60 [rpm])
Total/overall efficiency
Total efficiency: ηtot = ηvol × ηm
where
ηtot : total efficiency ηvol : volumetric efficiency ηm : mechanical/motor efficiency
Example (1)
A leakage of oil from a pump is 6% at 230 bar. Calculate the total efficiency if the flow rate at 0 bar is 10 dm3min-1 and the motor efficiency is 75%.
Solution:
Q (P = 0 bar) = 10 dm3min-1
Q (P = 230 bar) = 10 × 0.94 = 9.4 dm3min-1 ηmotor = 0.75, ηvol = 9.4/10 = 0.94
Therefore
ηtot = ηmotor × ηvol = 0.705 (= 70.5 %)
Example (2)
A pump has a displacement volume of 100 cm3. It delivers 0.0015 m3/s at 1000 rpm and 70 bars. The prime mover input torque is 120 Nm.
a) What is the overall efficiency of the pump?
b) What is the theoretical torque required to operate the pump?
Solution