MET230: Hydraulics and Pneumatics - Unit 2 Review Assignment 1

This document is a review assignment for the Hydraulics and Pneumatics course. It covers topics such as limited rotation hydraulic motors, gear motors, volumetric efficiency, hydraulic motors, hydraulic valves, and problem-solving exercises. The assignment includes multiple-choice questions and problems to solve.

MET230: Hydraulics and Pneumatics
Unit 2 Review Assignment 1
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Question 1
Which of the following statements is true about limited rotation hydraulic motors?
A. They are also called non-oscillating motors
B. They can’t rotate in the counter clockwise direction
C. They are classified as linear actuators
D. They rotate through less than one complete cycle
E. None of the above
Question 2
Which of the following statements lists the main advantages of gear motors?
A. Long expected life and zero maintenance
B. Highest volumetric and mechanical efficiencies
C. Simple design and subsequent low cost
D. High speed and high torque
E. None of the above
Question 3
Which of the following statements define the volumetric efficiency of a hydraulic motor?
A. Volumetric efficiency is the theoretical flow rate the motor should consume, divided by the
actual flow rate consumed by the motor.
B. Volumetric efficiency is the actual torque delivered by the motor, divided by the torque the
motor should theoretically deliver.
C. Volumetric efficiency is the actual power delivered by the motor, divided by the actual power
delivered to the motor.
D. There is no such thing as volumetric efficiency for a motor. This concept applies to pumps only
E. None of the above
Question 4
Which of the following is NOT true about hydraulic motors?
A. A motor uses more flow than it theoretically should
B. A hydraulic motor delivers less torque than it theoretically should
C. Hydraulic motors extract energy from a fluid and convert it to mechanical energy
D. In vane motors, vanes are held in contact with the cam ring by springs or by being pressure-
loaded
E. None of the above
Question 5
Which of the following is NOT true about hydraulic valves?
A. Directional control valves determine the path of a fluid in a given circuit
B. Pilot check valves can permit flow in the normally blocked opposite direction
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C. A pressure relief valve is used to limits the maximum pressure in a hydraulic system
D. Pressure reducing valve is another name for pressure relief valve
E. All of the above
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Problem 1
A rotary actuator has the following physical data:
Outer radius of rotor = 0.75 in
Outer radius of vane = 1.5 in
Width of vane = 0.75 in
If the torque load is 1000 in∙lb, what pressure must be developed to overcome the load?
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Problem 2
A hydraulic motor has 5.5-in3 volumetric displacement. If it has a pressure rating of 1500 psi and
receives oil from a 12.5-gpm theoretical flow-rate pump, find the motor
a. Speed
b. Theoretical torque
c. Theoretical horsepower
Solution
Speed
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Theoretical torque
Theoretical horsepower
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Problem 3
A hydraulic motor has a displacement of 140 cm3 and operates with a pressure of 110 bars and a speed
of 1800 rpm. If the actual flow rate consumed by the motor is 0.0048 m3/s and the actual torque
delivered by the motor is 210 N∙m, find
a. ηv
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b. ηm
c. ηo
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d. kW power delivered by the motor
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Problem 4
A hydraulic transmission operating at 110-bars pressure has the following characteristics
__________________________________________
Pump motor____
VD = 95 cm3 VD = ?
ηv = 82% ηv = 95%
ηm = 88% ηm = 93%
N = 900 rpm N = 550 rpm__
Find the
a. Displacement of the motor
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b. Motor output torque
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Problem 5
A pressure relief valve contains a poppet with a 0.8-in2 area on which system pressure acts. During
assembly, a spring with a spring constant of 2400 lb/in is installed in the valve to hold the poppet against
its seat. The Adjustment mechanism is then set so that the spring initially compresses 0.17 inches from
its free-length condition. In order to pass full pump flow through the valve at the PRV pressure setting,
the poppet must move 0.08 inches from its fully closed position. Determine the
a. Cracking pressure
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b. Full pump flow pressure (PRV pressure setting)
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Problem 6
A pressure relief valve has a pressure setting of 1800 psi. Compute the horsepower loss across this valve
if it returns all the flow back to the tank from a 27-gpm pump.
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Problem 7
An unloading valve is used to unload the pump of problem 6. If the pump discharge pressure during
unloading equals 28 psi, how much hydraulic horsepower is being wasted?
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Problem 8
A 1.75-in diameter sharp-edged orifice is placed in a pipeline to measure flow rate. If the measured
pressure drop is 70 psi and the fluid specific gravity is 0.85, find the flow rate in units of gpm.
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Problem 9
The figure in front shows flow versus pressure drops curves for four valves when the fluid has a specific
gravity of 0.88. What is the capacity coefficient of the valve identified by curve number 2 at a flow rate
of 6 gpm?
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Problem 10
The system shown below has a hydraulic cylinder with a suspended load W. The cylinder piston and the
rod diameters are 1.5 in and 0.75 in respectively. The pressure relief valve setting is 600 psi. Determine
pressure p2 for a constant cylinder speed if
a. W = 1500 lb
b. W = 0 (load is removed)
Figure for Problem 10
solution
For a constant cylinder speed, the summation of the forces on the hydraulic cylinder must
be equal to zero. thus we have ,
-W-P1AP+P2(AP-AR)=0 (Clime et al., 2015)
Where, P1=Pressure relief valvesetting=600 psi
AP= /4 (DP)2 = /4 (1.5)2 = 1.7671 in2=Area of piston.
AR= /4 (DP)2 = /4 (0.75)2 = 0.4419 in2= Area of rod.
AP-AR = 1.3252 in2
Case-(a):-
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if W=1500 lb
then put the value of W in equation below
-W-P1AP+P2(AP-AR)=0
-1500 -[600 * 1.7671]+[P2 (1.3252)]=0
By solving we get P2= 1931.98 psi
case(b):-
If W=0(load is removed)
0 -[600 * 1.7671]+[P2 (1.3252)]=0
By solving we get
P2= 800.08 psi
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References
Clime, L., Brassard, D., Geissler, M., & Veres, T. (2015). Active pneumatic control of
centrifugal microfluidic flows for lab-on-a-chip applications. Lab on a Chip, 15(11),
2400-2411.
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