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List 3 importan considerations when alanlyzing a hydraulic circuit.
- 1- Safty operation
- 2- Prerformance of desired function
- 3- Efficiency of operation
Purpose of a regenrative circuit
1- Is used to speed up the extending speed of a double acting hydraulic cylinder.
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.
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
Purpose of a check valve?
1- is to permit free flow in one direction and prevent any flow in the opposite direction.
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.
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
Why conductors and fittings should no be copper?
1- Because coppers promotes the oxidation of petroleum oils.
Know four primary types of conductors
- 1- Steel pipes
- 2- Steel tubing
- 3-Plastic tubing
- 4-Flexibible hoses
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
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.
Three basic types of acumulators
- 1- Separetor type
- 2- Non- separetor type
- 3- Pisto acumulator type
Three aplications of acumulators
- 1- An auxiliary power source
- 2- A leakage comensator
- 3An emergency power source
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.
Four tpes of materials used of seals.
- 1- Leather
- 2- Buna-N
- 3- Silicone
- 4- Neoprene
Two types of flow-measuring devices
- 1- Pressure gages
- 2- Flowmeters
Describe an intesifier
A pressure intesifier is used to eliminate the need for a high-pressure/low-flow pump.
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
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.
Disadvantages of fire-sesistant fluids
- 1- low viscosity
- 2- incompatibility with most natural or sinthetic rubbber seals
- 3-and high cost
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.
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
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
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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