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62 Cards in this Set
- Front
- Back
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Do not use________ parts in any hydraulic unit where they may come in contact with hydraulic oil |
zinc or cadmium plated |
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4 basic types of hydraulic pumps
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vane,piston,gear,screw
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The swashplate is also known as a______
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wobble plate
located in yoke does not move |
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Piston pumps are easily damaged by...
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contamination
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For screw pumps, leakage up to______a day is acceptable
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50ml
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If seal leakage exceeds allowable limit on screw pumps...
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replace the seal or use emergency packing
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Mechanical seal failure on screw pumps may be caused by....
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improper o-ring groove dimensions
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When disassembling pumps, Use extra care when handling the....
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carbon washer
any damage to it is cause for rejection |
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Common failure of mechanical seals is due to....
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-blistering/chipping of the rotating carbon seal face from heat buildup
-failed pump thrust ball bearing -improper mechanical seal cavity venting -improper clearance between piston and bushing |
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The least likely cause of mechanical seal failure is...
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excess clearance between the power rotor balance piston and balance piston bushing
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Reciprocating piston pumps can be designed to operate in one of two configurations
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Simplex-one direction of motion
Duplex-both directions of motion |
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Two types of hydraulic motors?
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vane or piston
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The most commonly used hydraulic motor is the...
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fixed displacement piston type
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3 types of hydraulic actuators
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cylinders,ram units, rotary
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Internal fluid leakage on actuators leak past the seals and into....
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the gear case chamber, after filling the chamber, it will then be forced out and become external leakage
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General causes of fluid leakage
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-seal failure
-grooving and scoring of the cylinder -defective seals -seal deterioration (from incompatable fluid) -seal deterioration (from mechanical wear or aging) |
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Major problem with piston type rotary actuators?
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external leakage
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All flexible rubber hose connections shall be replaced every...
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12 years
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The most basic flow control valve is the... |
stop valve |
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Most common types of stop valves are...
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globe
gate needle plug cocks |
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The needle valve may be used as a....
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-stop valve and for throttling the flow of fluid
-not used when accurate control of flow is required |
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Most common type of pressure control valve?
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relief valve
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Cracking or lifting pressure on relief valves?
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difference between inlet and outlet pressure
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Sequence Valves
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-control sequence of operation between two branches of a circuit
-after one actuator is activated, fluid is then sent to another |
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Replenishing Valves
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ensures hydraulic pump has adequate supply of fluid at all times
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Unloader Valves
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-used to direct flow of fluid from a pump to the work until a predetermined pressure is attained
-then discharges it back to tank |
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The return line should be piped...
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-directly to the reservior
-located as far as possible from the pump inlet |
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Directional valves
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used to direct flow of fluids in a system
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Most commonly used directional valve?
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4 way valve
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4 way directional valves are generally what type? |
closed center type or open center type |
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Servo Valves
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electrically operated directional valves
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Most common type of hydraulic fluids used?
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petroleum based
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Excessive foaming or entrainment of air in hydraulic fluid causes...
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a spongy system,cavitation,reduces heat absorption, speeds oxidation
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In addition to providing storage for the reserve of fluid needed for the system, the reservoir acts as...
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-a radiator for dissipating heat
-settling tank -allows entrained air to escape |
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The inside of the reservoir will generally have...
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baffles
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Heated hydraulic fluid causes... |
an increase of internal and external leakage |
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Two basic types of heat exchangers
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fluid to water type
fluid to air type |
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Generally it is desirable to keep hydraulic fluid to a minimum temperature of... |
104°F |
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Accumulators
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a pressure storage reservoir in which hydraulic fluid is kept under pressure
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Accumulators are used for...
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hydraulic shock suppression
fluid make up leakage compensation emergency power holding high pressure with no pump |
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Types of accumulators
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piston
bag or bladder direct contact gas over fluid |
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The smallest particle visible to the human eye is...
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40 microns
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The most common contaminant in a hydraulic system is...
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water
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Water in hydraulic fluid generally comes from...
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condensation in reservoirs
failure of piping contaminated oil |
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A water content less than_____is desirable in hydraulic fluid
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100 ppm
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The max allowable water content for hydraulic fluid is...
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500 ppm
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Samples must be drawn...
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-on a running system or at normal operating temperatures
-from a hose assembly -pump discharge gauge line when sampling port is unavaliable |
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The first oil coming from the sampling port should be....
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discarded (might not represent system)
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Samples are not to be taken from....
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-tops of reservoirs
-where contamination levels are low |
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In general, newly installed seals should...
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not leak
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Hydraulic symbols used in standard drawings are shown in the______position |
At rest |
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What are the two primary locations for hydraulic filters |
-Pump discharge side -Reservior return -High pressure side -Low pressure side |
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What is occuring is a hydraulic filter indicator is showing red? |
Filtration has ceased, immediate action required |
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3 general categories for hydraulic contamination |
-built in -ingress -internally generated |
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Most of the harmful contamination in hydraulic fluid is considerably less than.... |
40 microns |
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What is NOT a component of a hydraulic reservior |
Acidity indicator |
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What material is NOT used in the reinforcement layer of hydraulic hose? |
Stainless steel |
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2 main purposes of a hydraulic accumulator |
Acts as a hydraulic shock absorber Provides auxiliary power source |
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What is commonly used when cutting a hose during fabrication? |
Fine tooth hacksaw or cutoff wheel |
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2 designs of a hydraulic piston pump? |
-radial -axial |
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The angled_____plate creates the reciprocating motion in the pistons and controls the displacement of the pump by controlling the piston stroke length |
Swash |
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What component in a hydraulic system converts hydraulic energy to mechanical energy? |
Actuator |
