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68 Cards in this Set
- Front
- Back
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With increasing temperature, what does the density of a liquid do? |
Decreases slightly. |
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What does pressure equal? |
Pressure equals force times area. P=FxA |
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Is bore radius or diameter? |
Bore=Diameter. |
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What's the area of a circle? |
Pi•r^2 |
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When temp goes up, what does he viscosity of a liquid do? |
Decreases slightly. |
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What does high viscosity in hydraulic fluid result in? |
Sluggish operation, increased power consumption, high temp. |
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What's the law of conservation of energy? |
Energy cannot be created or destroyed. |
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What devise measures absolute pressure? |
Manometer |
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What do baffles do? |
Act as cooling fins for heat transfer, keep impurities from recycling, ease flow from inlet to outlet. |
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Force over distance is what unit? |
Work |
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Pressure is measured in? |
PSI |
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What do circles represent in hydraulic schematics? |
Pumps and Motors. |
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What are dashed lines on hydraulic blueprints? |
Pilot lines. |
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Absolute pressure equals what? |
Gauge pressure plus atmospheric pressure |
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Standard Air pressure is what? |
14.7 psi |
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Change in potential energy equals what? |
Force times distance. |
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What is power? |
Torque • angular velocity Work / time Energy / time |
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What is hydraulic pressure? |
Atmospheric pressure plus system pressure. |
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What is stress? |
Change in length / original length. |
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What determines pump size needed in hydraulic circuit? |
Actuator size, actuator speed, and actuator load. |
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Pneumatic systems typically operate at what pressure? |
Under 250 psi |
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Besides compression air, what needs to happen in a pneumatic system? |
Filtration, cooling, and water vapor removal. |
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Liquid enters and is forced out of a pump by? |
Generating an increasing and decreasing volume. |
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What's the function of a pressure relief valve in a hydraulic system? |
To unload the punk and to divert the flow to the tank. |
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What are pressure valves used for in a hydraulic circuits? |
Provide safety release for deadheaded system and to reduce pressure on an actuator. |
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Hydraulic accumulators can be? |
Spring loaded, weighted, and gas pressurized. |
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What are hydraulic accumulators used for? |
Supply oil to a system, maintain pressure in a system, and absorb shock in a system. |
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Besides load, what is resistance to flow caused by in a hydraulic system? |
Hose size, line restrictions, and changing direction. |
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What's the law of conservation? |
Energy can't be created or destroyed, just changed. |
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What's viscosity? |
The resistance to flow. |
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What's the unit of measurement for viscosity? |
The saybolt. (SUS or SSU) |
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How is viscosity related to temperature? |
They're inversely related. |
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How is viscosity related to pressure? |
Directly. |
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What is density? |
Mass of air molecules per unit volume. |
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What is temperature? |
Measure of speed of molecules. |
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How are pressure, temperature, and density related? (equation) |
Pressure equals (gas constant) x density x temperature. |
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What is work? |
Application of force to cause movement through a distance. |
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What's the unit of measure for work? |
Ft lb or joule (Newton meter) |
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What's the equation for work? |
Work = distance x force |
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What's power? |
The speed that work is done. |
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What's the unit of measurement for power? |
Horsepower. HP. |
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What's the equation for power? |
Power = (distance x force)/time |
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What's the equation for force? |
Force = pressure x area |
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What's the area of a circle? |
Πr^2 |
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What's the difference between velocity and flow rate? |
Velocity is two dimensional. Feet per second. Flow rate is three dimensional. Includes volume. Gallons per second. |
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What does an accumulator do? |
Stores pressure. |
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What sort of energy is stored in an accumulator? |
Potential energy. |
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What are the three types of accumulators? |
Weight loaded, spring loaded, and hydro-pneumatic. |
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How does a weight loaded accumulator work? |
They maintain force by means if heavy weights acting in a piston or ram. |
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Are weight loaded accumulators big or small? |
Big. |
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Where are weight loaded accumulators generally used? |
Central hydraulic systems. |
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How do spring loaded accumulators work? |
Applies force to liquid by means if a spring acting on a piston. |
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Are spring losses accumulators big or small? |
Small. |
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What are spring loaded accumulators generally used for? |
Individual hydraulic systems at lower temperatures. |
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What is fluid pressure determined by in a spring loaded accumulator? |
By compression rate if the spring. |
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What are three purposes of an accumulator? |
Stores pressure, supplements flow, prevents system shock. |
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Where and why are spring loaded accumulators vented? |
On the spring side to prevent accumulation of leakage fluid. |
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How do hydro-pneumatic accumulators apply force? |
By using compressed gas. |
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What's the most common accumulator in hydraulic systems? |
Hydro-pneumatic. |
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For hydro-pneumatic accumulators, what's always used in hydraulic systems? |
Dry nitrogen. |
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For hydro-pneumatic accumulators, what's never used in hydraulic systems? Why? |
Compressed Air. Because it will explode. |
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What are the three types of hydro-pneumatic accumulators? |
Piston, diaphragm, and bladder types. |
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What is atmospheric pressure at sea level in inches of mercury? |
29.92 |
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When higher than sea level, what will you measure in inches of mercury? |
Less than 29.92 |
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What is atmospheric pressure? |
14.7 psi |
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What is absolute pressure? |
Starts at absence of atmospheric pressure. |
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What's the equation for gage pressure? |
Gage pressure = absolute pressure + atmospheric pressure. |
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What is bore? |
Diameter. |
