HYDR Exam

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Anonymous
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116720
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HYDR Exam
Updated:
2011-11-14 14:32:13
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Exam III
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  1. List 3 importan considerations when alanlyzing a hydraulic circuit.
    • 1- Safty operation
    • 2- Prerformance of desired function
    • 3- Efficiency of operation
  2. Purpose of a regenrative circuit
    1- Is used to speed up the extending speed of a double acting hydraulic cylinder.
  3. What is meant by an air over oil system
    1- A system that used pressurized compressed air to eliminated sthe need for a costly hydraulic pump and tank unit.
  4. What is a mechanical hydraulic servo system?
    1- Is a system that messure its own outpout and forces the output to quickly and accurately follows a comand signal. Example: power-steering system in a car
  5. Purpose of a check valve?
    1- is to permit free flow in one direction and prevent any flow in the opposite direction.
  6. Flow velocity recomended for the discharge side of a pump.
    1- Recomended is 4 ft/s in order to prevent excesively low suction pressures and resluting pump cavitation.
  7. Flow velocity recommended for the Inlet side of a pump
    1- Recomended 20 ft/s in order to prevent turbulent flow and the corresponding excessive head losses and elevated fluid temperatures
  8. Why conductors and fittings should no be copper?
    1- Because coppers promotes the oxidation of petroleum oils.
  9. Know four primary types of conductors
    • 1- Steel pipes
    • 2- Steel tubing
    • 3-Plastic tubing
    • 4-Flexibible hoses
  10. Three factors that should be considered when installing flexible hoses?
    • 1-Provie some slack to allow for shrinkage or expansion.
    • 2- Use brackets and clamps to keep hoses in place
    • 3- Provide enough hose for a wide radius curve
  11. Four criteria by which the size of a reservoir is determined.
    • 1- To allows for dirt and chips to settle to the bottom
    • 2- To allows entrained air to escape from oil.
    • 3- To hold all the oil that might drain into the reservoir from the system
    • 4- It should have adequate air space to allow for thermal expansion of the oil.
  12. Three basic types of acumulators
    • 1- Separetor type
    • 2- Non- separetor type
    • 3- Pisto acumulator type
  13. Three aplications of acumulators
    • 1- An auxiliary power source
    • 2- A leakage comensator
    • 3An emergency power source
  14. Diference between static and dynamic seal
    • Static: are used between mating parts that do not move relative to each other.
    • Dynamic: are assembled between mating parts that move relative to each other.
  15. Four tpes of materials used of seals.
    • 1- Leather
    • 2- Buna-N
    • 3- Silicone
    • 4- Neoprene
  16. Two types of flow-measuring devices
    • 1- Pressure gages
    • 2- Flowmeters
  17. Describe an intesifier
    A pressure intesifier is used to eliminate the need for a high-pressure/low-flow pump.
  18. Five most common causes of failure in a hydraulic system
    • 1- Clogged or dirty oil filters
    • 2- Inadequate supply of oil in the reservoir
    • 3- Leaking seals
    • 4- Loose inlet lines
    • 5- Incorrrect type of oil
  19. Define Flash point, Fire point and Autogenous ingnition temperature.
    • Flash point: the temperature at which the oil surface gives off sufficient vapors to ingite when a flame is passed over the surface
    • Fire point: the temperature at which the oil will release sufficient vapor to support combustion continuously for five seconds when a flame is passed over the surface.
    • Autogenous ignition temperature: The tempreture at which ignition occurs spontaneously.
  20. Disadvantages of fire-sesistant fluids
    • 1- low viscosity
    • 2- incompatibility with most natural or sinthetic rubbber seals
    • 3-and high cost
  21. Difference between a filter and a strainer
    • Filter: is to retain by some porous medum, insoluble contaminants fro fluids
    • Strainers: are constructed of a wire screen that rerely contains openings less than 100 mesh.
  22. Four things that can cause a noisy pump
    • 1- Air entering pump inlet
    • 2- Excessive oil viscosity
    • 3- Dirty inlet strainer
    • 4- Excessive pump speed
  23. Four things that can cause low or erratic pressure
    • 1- Air in the fluid
    • 2- Pressure relief valve set too low
    • 3- Leak in hydaulic line
    • 4- Defective or worn pump
  24. Four things that can cuse NO presure
    • 1- Pump turning in wrong direction
    • 2- Rupture hydraulic line
    • 3- Low oil level in reresvoir
    • 4- Broken pump shaft

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