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Chapter 9: Fluidity Power

Terms in this set (10)

When analyzing or designing a hydraulic circuit, what are the three most important considerations?
Safety of operation, Performance of desired function, and Efficiency of operation
Under what condition is a hydraulic motor braking system desirable?
If the motor is driving a machine (Example: index table) that has a large amount of inertia, this would create a flywheel effect on the motor and cutting off the flow of fluid to the motor would cause it to act as a pump and create excessive internal pressures. A brake circuit would provide fluid to the motor, while creating a controlled back-pressure on the outlet of the motor.
What is the purpose of a regenerative circuit?
They allow for more efficient operation at a reduced actuator speed.
What is the purpose of the check valve in the circuit below?
Prevents the smaller displacement pump from being unloaded along with the larger displacement pump at higher pressures and allows for the "Hi-Low" double-pump system to operate properly
For the circuit below, the motions of the two cylinders are synchronized in the extension strokes. Are the motions of the two cylinders also synchronized in the retraction strokes? Explain why?
Yes, because the cylinders are connected in parallel and the flows are evenly split between the two cylinders
Note: v1 = v2 for the extension and retraction strokes when AP1-AR1 = AP2
When the directional control valve in the system below returns to its center position, the cylinder rod moves in a given direction, Is this direction extensive of retraction? During the movement determine the force and velocity.
This is a regenerative system, so the cylinder extends
- The Velocity of the piston is 9.81 in/s
- The Force is 785 lbf
What is wrong with the circuit below?
Hint: This is an unloading valve, not a relief valve.
A check valve is needed in the hydraulic line just upstream from where the pilot line to the unloading valve is connected to the hydraulic line. Otherwise, the unloading valve would behave like a pressure relief valve and thus, energy would be wasted
What unique features does the circuit below provide in the operation of the hydraulic cylinder?
) It provides mid-stroke stop and hold capability of the hydraulic cylinder's position (during either extend or retract) by deactivating the 4-way, 3-position, directional control valve.
2) Provides two speeds of operation during the extend stroke, because when the 3-way, 2-position DCV is unactuated (in spring offset position) the extend speed is normal, but when the 3-way, 2-position DCV is actuated, the extension speed is increased due to the regenerative capability of the circuit (though cylinder force is reduced).
For the system below (regarding the extension strokes of the cylinders), what pump pressure is required if the cylinder loads are 5000 lb each, the piston area of cylinder 2 is equal to the difference between the areas of the piston diameter and rod diameter for cylinder 1 (which means they will be perfectly synchronized), and cylinder #1 has a piston area of 10 sq-inches?
2000 psi
For the meter-in flow control valve system shown below, the following data are given:
- Desired cylinder speed is 10 in/sec
- Cylinder piston diameter is 2 inches (area = 3.14 sq-in)
- Cylinder load = 3000 lb
- Specific gravity of oil is 0.90
- Pressure relief valve setting is 1000 psi
Determine the required capacity coefficient of the flow control valve.
Hints:
1) Use equation 9-9 and note that the units for C are gpm/SQRTpsi
2) Q = vcyl x Apiston
1.15
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