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Questions and Answers
What is the effect of applying pressure to a confined liquid in a hydraulic system?
What is the effect of applying pressure to a confined liquid in a hydraulic system?
The force is transmitted equally and undiminished throughout the containing vessel.
In what scenario would a pilot-operated relief valve be more advantageous than a direct acting relief valve?
In what scenario would a pilot-operated relief valve be more advantageous than a direct acting relief valve?
Pilot-operated relief valves are advantageous in managing higher flow rates while controlling larger pressures more precisely.
How does the size of the inlet port of a non-variable fixed displacement pump compare to its outlet port?
How does the size of the inlet port of a non-variable fixed displacement pump compare to its outlet port?
The inlet port is larger than the outlet port.
What are the initial steps to disassemble a hydraulic cylinder?
What are the initial steps to disassemble a hydraulic cylinder?
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What happens to the velocity of fluid in a hydraulic system when it flows through a hose that has a decreased diameter?
What happens to the velocity of fluid in a hydraulic system when it flows through a hose that has a decreased diameter?
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What factors determine the flow rate in a hydraulic circuit?
What factors determine the flow rate in a hydraulic circuit?
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What occurs to pressure in a confined liquid when head pressure is applied?
What occurs to pressure in a confined liquid when head pressure is applied?
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How is the force in a hydraulic system calculated using pressure and area?
How is the force in a hydraulic system calculated using pressure and area?
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What is the primary function of hydraulic fluid within a hydraulic system?
What is the primary function of hydraulic fluid within a hydraulic system?
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What happens to the hydraulic system's flow rate if the orifice experiences continuous oil flow?
What happens to the hydraulic system's flow rate if the orifice experiences continuous oil flow?
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How do you calculate the force exerted by a piston in a hydraulic system?
How do you calculate the force exerted by a piston in a hydraulic system?
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Why is the return line placed below the surface of the fluid in a hydraulic reservoir?
Why is the return line placed below the surface of the fluid in a hydraulic reservoir?
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What must be released before removing a gas-charged accumulator from a hydraulic system?
What must be released before removing a gas-charged accumulator from a hydraulic system?
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What is one key advantage of using a manifold block with cartridge valves in a hydraulic system?
What is one key advantage of using a manifold block with cartridge valves in a hydraulic system?
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What does hydraulic oil viscosity indicate about the fluid?
What does hydraulic oil viscosity indicate about the fluid?
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What special feature does an O-ring seal have for use in dynamic pressure applications?
What special feature does an O-ring seal have for use in dynamic pressure applications?
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What happens to fluid flow when a closed-center spool valve is placed in the neutral position?
What happens to fluid flow when a closed-center spool valve is placed in the neutral position?
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How is the output of a variable displacement axial piston pump modified?
How is the output of a variable displacement axial piston pump modified?
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What is the relationship between a hydraulic pump's flow rate and hydraulic pressure?
What is the relationship between a hydraulic pump's flow rate and hydraulic pressure?
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What is a primary advantage of a pilot-operated relief valve over a direct relief valve?
What is a primary advantage of a pilot-operated relief valve over a direct relief valve?
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Why is the reservoir supply port to the pump located 1 inch from the bottom?
Why is the reservoir supply port to the pump located 1 inch from the bottom?
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What is the function of a pressure reducing valve in a hydraulic system?
What is the function of a pressure reducing valve in a hydraulic system?
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How do you classify hydraulic pumps based on their ability to create flow?
How do you classify hydraulic pumps based on their ability to create flow?
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What determines the speed of a hydraulic cylinder?
What determines the speed of a hydraulic cylinder?
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What characteristic of a single-acting hydraulic cylinder is significant?
What characteristic of a single-acting hydraulic cylinder is significant?
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What is the primary function of hydraulic oil coolers?
What is the primary function of hydraulic oil coolers?
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What does it indicate when hydraulic oil appears milky-colored?
What does it indicate when hydraulic oil appears milky-colored?
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What type of valve restricts the amount of fluid flowing in a hydraulic system?
What type of valve restricts the amount of fluid flowing in a hydraulic system?
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What is meant by the term 'cracking pressure' in relation to relief valves?
What is meant by the term 'cracking pressure' in relation to relief valves?
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What component is responsible for converting fluid power into mechanical power in a hydraulic system?
What component is responsible for converting fluid power into mechanical power in a hydraulic system?
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What must be done to a gas-charged accumulator before removal from the system?
What must be done to a gas-charged accumulator before removal from the system?
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Study Notes
Hydraulic Systems - Study Notes
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Hydraulic Fluid Pressure:
- Atmospheric Pressure: Pushes hydraulic fluid towards the pump inlet.
- Head Pressure: Pressure at the bottom of a standing liquid.
- Pressure Transmission: Force applied to a confined liquid is transmitted equally and undiminished throughout the containing vessel.
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Force Calculation:
- Force (F) = Pressure (P) x Area (A): Used to determine piston force.
- Example: 30 psi applied to a 5-inch squared piston results in 150 pounds force (667.23 Newtons).
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Flow Rate:
- Definition: Volume of fluid moving through a system per unit time.
- Measurement: Flow gauges, or pump speeds.
- Effect of Hose Diameter: Decreased hose diameter increases fluid velocity.
- Pump Output: Determines the rate of flow.
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Fluid Velocity: Rate of speed past a given point at a given time.
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Pascal's Law: Force applied to a confined fluid is transmitted equally and undiminished in all directions.
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Relief Valves:
- Direct Acting Relief Valve: Operates directly via spring force, opens immediately when pressure exceeds the spring setting.
- Pilot Operated Relief Valve: Uses a small pilot valve to control a larger valve, opens immediately when pressure exceeds the spring setting.
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Pump Types and Function:
- Fixed Displacement Pumps: Produce a constant flow rate.
- Variable Displacement Pumps: Used in closed-center systems, and adjustable flow.
- Open Center Systems: Pumps produce continuous flow
- Closed Centre Systems: Pumps produce flow when needed.
- Purpose: To pump hydraulic fluid and create flow in a system.
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Reservoir Considerations:
- Return Line Submergence: Prevents aeration of the fluid.
- Pressurized Reservoirs: Aid in supplying the pump with fluid.
- Inlet Port Location: Reservoir supply port is 1 inch from the bottom to prevent sediment entry into the pump.
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Cylinder Force and Speed:
- Force: Increased with larger bore of cylinder with a diameter piston.
- Stroke and Speed: Slower movement is seen with larger cylinders, increased fluid demand.
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Hydraulic Fluid Function: Transmits power within the system.
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Troubleshooting Piston Seals:
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Valve Types:
- Directional Control Valves: Open center and close center.
- Pressure Relief Valve: Protects the hydraulic system from overpressure.
- Pressure Reducing Valve: Supplies one circuit with lower pressure than system pressure.
- Flow Control Valve: Restricts fluid flow.
- Bypass Valve: Protects cooler in oil-water heat exchange systems.
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Cylinder Types:
- Single Acting: One-way operation
- Double Acting: Force for both extension/retraction (balanced/unbalanced)
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Actuators: Convert fluid power to mechanical power.
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Filters: Spin and Cartridge filters.
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Hydraulic Motors: Convert hydraulic flow and pressure into mechanical rotational force.
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Seals:
- Static Seals: Non-moving parts
- Dynamic Seals: Moving parts (Radial lip seals, o-rings).
- Exclusion Seals: Prevent entry of contaminants.
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Accumulator Considerations: Gas charged accumulators: nitrogen is the common gas used; release both hydraulic and accumulated pressure before removing
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Hydraulic Oil Considerations:
- Viscosity: Measures its resistance to fluid flow.
- Contamination: Milky oil indicates water contamination.
- Oil Oxidation: Starts above 125°C (250°F).
- Drainage: Drain oil at operating temperature.
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General Maintenance:
- Storage: Keep components covered/maintained with appropriate caps
- **Routing:**Hoses should be free of kinks or tight bends.
- Preparing for Service: Lock out, lower attachments, shut down engine, and cycle controls involved.
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Troubleshooting:
- Smaller-Diameter Hoses: Increased velocity and temperature.
- Variable Displacement Pumps: Flow rate is adjusted via swashplate angle.
- Flow Rate and Pump Output: Constant for fixed displacement pumps. Dependent on the swashplate angle for variable displacement pump.
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Component Interactions:
- Pressure: Result of resistance to flow.
- Manifold Blocks and Cartridge Valver: Advantage for more simplified system control.
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Hydraulic Machine Preparation for Service:
- Lock out protocol, safety precautions must be put in place before any fluid removal or component removal or reconnection.
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Hydraulic Fluids:
- Purpose: Transmits power in a hydraulic system.
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Hydraulic Pumps:
- Types: Fixed displacement and variable displacement classified based on flow capabilities.
- Rating Criteria: Flow rate, pressure, displacement.
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Description
This quiz covers key concepts in hydraulic systems, focusing on fluid pressure, force calculation, and flow rate. Gain a deeper understanding of Pascal's Law and the implications of fluid dynamics in hydraulic applications. Ideal for students and professionals in engineering and physics.
