Jasons Review Flashcards
What best describes a three-way/two position valve?
It can be used when air needs to be released when valve is closed
Bleed Off Flow Control is _____________ energy efficient than meter-in or meter-out flow control.
More
Bleed Off Flow Control is most efficient
What does an open top indicate with an oil reservoir symbol?
It is vented to atmosphere
True or False;
Pilot-To-Open check valves are Normally Closed?
True
“lock valves”
With hydraulic systems, pump inlets should be ___________ than the discharge lines.
Larger Diameter
A pressurized hydraulic reservoir can be used to solve which problem?
Cavitation
What best describes a counterbalance valve?
They are used to prevent a load suspended by a cylinder from free fall.
What best describes a check valve?
They are used to prevent reversal of fluid flow
What is an example of a positive seal?
Connector fittings on pipe tubes and housing
What is a cause of aeration?
Leaking pump inlet fittings
Low hydraulic fluid levels
Turbulence in the tank
When does cavitation occur?
When fluid moves from a low pressure area to a high pressure area.
If hydraulic pipe is changed out and replaced with a pipe that has a smaller inside diameter, the speed of the fluid will?
Increase
Bernoullis Principle - speed up, pressure down
What will not control the output of a hydraulic pump?
Increase relief valve setting
How can you control the output of a hydraulic pump?
Use a variable displacement pump
change the speed of the driver
use a pressure compensation pump
What does a diagonal arrow on a hydraulic symbol always indicate?
its variable in its output
What does the term pressure override refer to with a pressure relief valve?
The difference between cracking pressure(first drop through), and full flow pressure to fully open the valve.
What occurs in an inline axial piston motor when the swash plate is at maximum angle?
Low Speed, High Torque
A hydraulic sequence valve must be installed so that the inlet of the valve is connected to the _________ cylinder and the outlet to the _________ cylinder.
First
Second
Sequence Valve has drain*
The advantage of using a proportional directional control valve is that they can also:
Control Flow
notes
-solenoid controlled
-infinitely variable
horizontal lines above and below dcv indicate proportional dcv.
With a proportional dcv the spool movement is proportional to?
the electrical input from amplifier card
What best describes an unloading valve?
They are used to depressurize part of a system and often used to circulate fluid at low pressure.
-saves energy
With accumulators used for energy storage applications, pre-charge to ______% of minimum system pressure.
90% for energy storage
75% for shock
70% for pulsations
What does a filter with a beta ratio of 15 indicate?
it allows 1 particle to escape for every 15 that enter the filter.
15:1
What should be checked if a hydraulic cylinder has hot spots?
Leaking piston seals
-also be loss of speed.
What best describes a pressure reducing valve?
They are normally open valves that are actuated by pressure in a branch of the circuit in which they are installed
-pilot at outlet
-normally open
-drain
Flow is produced by a ________ across an oriface.
Pressure drop
flow - goes high pressure to low pressure
What is the definition of Power?
The rate at which work is done
How is efficiency % found?
Output over input times 100
In a hydrostatic(closed loop) system, what returns the case drain oil to the main pump?
Charge pump
-charges inlet so you don’t get cavitation
In a solenoid controlled, pilot operated DCV the main stage actuation method is?
Hydraulic pressure
-piggy back valve, electric over hydraulic
What pumps cannot be variable in volume?
External gear pump
*all gear pumps are fixed.
A bypass compensator flow control valve can only be used in what location?
Meter-In
What harms to a hydraulic system does gum and varnish create?
Sticky Valves
What is a major advantage of a vertical mount pump and reservoir system?
Being inside the reservoir maintains stability and cleanliness of the pump.
True or False;
A balanced vane pump has much more compact design than an unbalanced vane pump.
True
True or False;
Oil from an air compressor in a pneumatic system aids in system lubrication.
False
When using a load sensing pump, the system pressure will never rise above;
Compensator setting
Load Sensing - Load + Setting when moving
max pressure determined by pressure compensator.
What piping material is suitable for pneumatic systems but not hydraulic?
Copper
*never use Teflon, Copper, Galvanized for hydraulics.
The resetting of a maximum pressure relief valve too high may cause?
Broken components
What is used to prevent a runaway situation on a hydraulic motor?
The external sensing pilot line on a brake valve.
Brake Valve:
Internal and External pilot lines
External - prevent runaway loads
Internal - Dynamic Braking (like abs in car)
Actuator speed can be decreased by?
Decreasing Flow
Servo valves require?
Pressure line filter with no bypass.
What is the diameter of a hydraulic hose with the marking of DASH 8?
1/2”
8/16 = 1/2
Which of the following is a directional control valve?
- Pressure Relief Valve
-Check Valve
-Needle Valve
-Sequence Valve
Check Valve
Which Valves require an external drain?
Pressure Reducing Valve
Sequence Valve
What valve only allows flow in one direction?
One-way valve
-check valve
What type of valves use a spring loaded ball?
Directional Valve
-check valve
What valve is piloted at its outlet and limits pressure downstream?
Pressure Reducing Valve
What is the optimal crush on hydraulic o-rings?
10%
How do you change the output of an adjustable vane pump?
Adjust the cam ring
-eccentric cam ring
What limits system pressure in a hydraulic system when using a fixed displacement pump?
Maximum Pressure Relief Valve
What valve allows a pump to operate at low pressure?
Unloading Valve
Hydraulic symbol:
cylinder with ram
cushion on cap end
diagonal arrow through cap end of cylinder
Cushion cylinder in cap end when retraction.
adjustable because of the arrow?
Question 56 on Jason review test.
The NUMBER 1 cause of wear in pumps is?
Contaminants
The angle of a hydraulic JIC fitting is?
37 degrees
Leaking pumps cause;
Heat increase and speed reduction
Pilot to Open check valves are used to;
Lock cylinders
Throttle valves control;
Speed
A brown sticky substance on a hydraulic valve is;
Gum and Varnish
The instrument most commonly used to establish a straight reference line of sight is a;
Alignment telescope
The procedure for checking the plumb accuracy of a jig transit or theodolite can be accomplished by using a;
Heavy plumb bob hanging on a wire in a bucket of oil
Horizontal wire alignment, when done correctly, can provide an accuracy as close as;
0.0001”
Jasons headphone battery dude
When performing an alignment with a laser unit, sudden temperature changes will…..
Reduce the accuracy of the unit
When referring to alignment procedures, the term plumb refers to a reference aligned to the _______ plane
to the vertical plane.
The lens of a magnifying glass is a
convex lens
A pentaprism is the basis of what tool?
Optical Square
-accessory for the alignment telescope
What laser alignment system requires two cables to operate?
Dual Beam/Dual detectors
-no dynamic interruption
First step in performing a machine alignment with lasers?
Rough alignment with straight edge
The term square refers to a reference aligned;
90 degrees to the reference line
Optical instrument to measure angles in 2 planes.
Theodolite
A laser alignment unit that is ________ safe can be used in an area that may have explosive gas present.
Intrinsically
What accessory is required to perform bucking in?
Precision lateral adjuster
Optical Plumbs are used to:
Set up instrument over a spot on the ground
What type of pneumatic valve produces an output only when it has two equal pressured inputs?
Dual Pressure Valve - “AND”
The rpms of a pneumatic tool are determined by;
Flow rate
rpm=speed
torque=pressure
What pneumatic piping system is subject to air starvation downstream when the upstream demand is heavy?
GRID
loop system is best
Quick Exhaust valves are used to;
Decrease cycle time of a cylinder
AKA
MOVE FASTER
An air regulator is normally ______ and piloted at its _______
Normally Open and piloted at its outlet.
