Hydraulics Flashcards
What are the 4 main dangers of hydraulics?
Injection
Toxins
Heat
Material movement
What are the dangers of pressures around and above 100psi?
Skin punctures
What are the dangers of pressures between 2000-7000psi?
Amputation
What should you use to check for leaks on a hydraulic system?
Paper or cardboard
Can you check for flow in a hydraulic system by cracking lines?
No
How large should a hydraulic reservoir be?
2-3x greater than systems capacity (not including reservoir)
Why does a hydraulic reservoir need to be 2-3x greater than the system capacity?
Leaking
Cooling
Air removal
Particulates (contaminants to settle)
What is spectromatic in terms of hydraulics?
Oil analysis
Testing oil for foreign matter
What is oil analysis?
Testing oil for foreign matter
Why do oil return lines have a 45 degree opening?
Natural circulation
Changes velocity
Why are filters typically on return lines?
Lower pressure = lower wear on filters
That’s where the particles in the oil are
Why should you always clean around a hydraulic system prior to opening it?
To ensure you don’t introduce any new contaminates
What is the difference between a strainer compared to a filter on a hydraulic system?
More course
On suction side of system
What are the two sides to a hydraulic system?
Pressure
Return
Why is the return side to a hydraulic system more simplistic?
Minimize chances for blockages
What type of piping should you NEVER use on a hydraulic system?
Galvanized or conducts
Why should galvanized or conduct pipes NOT be used on a hydraulic system?
You want interior piping to be as clean as possible
What is fluid?
Any liquid or gas that transmits power
Will take the shape of its container
What is the 4 main purposes of hydraulic fluid?
Transmit power
Lubricate moving parts
Seal clearances between parts
Cool/dissipate heat
How is moisture pulled into oil?
Temperature changes
Why should return lines be under the fluid line of the supply tank?
reduces aeration
Improve circulation
What is pour point in terms of hydraulics?
The lowest point a oil flows
What is viscosity index?
Measure of fluids resistance to viscosity change over temperature
What is boundary lubrication?
The ability for oil to stick to parts acting as a barrier
What is oxidation in terms of hydraulics?
Chemical reaction between oxygen and hydraulic fluid reducing the oil life
What does viscosity refer to?
Resistance to flow
Where should a relief valve always be located on a hydraulic system?
Directly after a pump
What are the 4 main valve controls?
Closed
Open
Tandom
Floating
If a solenoid fails on a hydraulic system should it be repaired or replaced?
Replaced
How should gauges be sized?
So the normal running operations read at 50% of the gauge
What is used in conjunction with an accumulator on a hydraulic system?
Shuttle valve
What is a shuttle valve?
Dual acting check valve
How many inches cubed is 1 US gallon?
231inches cubed
How many US gallons is 231 inches cubed?
1 gallon = 231 inches cubed
How many inches cubed is 1 imperial gallon?
277 inches cubed = 1 imperial gallon
What is 277 inches cubed equal to?
1 imperial gallon
How do you find the area of a circle?
3.14 x radius squared
What hydraulic symbol is this?
Main line
What hydraulic symbol is this?
Return line
What hydraulic symbol is this?
Control valve
3 position
What does this hydraulic symbol mean?
Line or conductors connecting
What does this hydraulic symbol mean?
Conditioning
(Ie. Filter, lubricator)
What does this hydraulic symbol mean?
Spring
What does this hydraulic symbol mean?
Unidirectional
Fixed capacity
Hydraulic pump
What does unidirectional mean?
One direction
What does bi directional mean?
Two directions
What does this hydraulic symbol mean?
Unidirectional
Hydraulic pump
Variable capacity
What does this hydraulic symbol mean?
Bi directional
Hydraulic pump
Variable capacity
What does this hydraulic symbol mean?
Bi directional
Hydraulic pump
Fixed capacity
What does this hydraulic symbol mean?
Bi directional
Hydraulic motor
Fixed capacity
What does this hydraulic symbol mean?
Bi directional
Hydraulic motor
Variable capacity
What does this hydraulic symbol mean?
Hydraulic motor
Uni directional
Variable capacity
What does this symbol mean?
Hydraulic
Oscillating motor
What does this hydraulic symbol mean?
Single acting
Cylinder
Return by un known source
What does this hydraulic symbol mean?
Single acting
Cylinder
Spring return
What does this hydraulic symbol mean?
Double acting
Cylinder
Double ended piston rod
What does this symbol mean?
Double acting
Cylinder
What does this hydraulic symbol mean?
Double acting cylinder
Double fixed cushion
What does this hydraulic symbol mean?
Double acting cylinder
Double adjustable cushion
What does this hydraulic symbol mean?
Check valve
Non return
What does this hydraulic symbol mean?
Check valve
Spring return
What does this hydraulic symbol mean?
Shuttle valve
What does this hydraulic symbol mean?
Flexible hose
What does this hydraulic symbol mean?
Electric motor
What does this hydraulic symbol mean?
Accumulator
Spring loaded
What does this symbol mean?
Accumulator
Gas charged
What does this symbol mean?
Accumulator
Weighted
What does this hydraulic symbol mean?
Reservoir/ tank
Vented
What does this hydraulic symbol mean?
Reservoir / tank
Pressurized
What does this hydraulic symbol mean?
Reservoir/ tank
Inlet pipe below fluid level
Vented
What type of valve is this?
Brake valve
Where in a hydraulic system would you find a brake valve?
Right after the motor
What type of valve is this?
Counter balance valve
Where is the counterbalance valve in a hydraulic system?
Directly after an actuator
What type of valve is this?
Sequence valve
Where is a sequence valve located in a hydraulic system?
Between different actuators
What valve is this?
Unloading relief valve
Where are unloading relief valves typically located?
After actuator on return line to reservoir
What type of valve is this?
Direct relief valve
Where are direct relief valves typically found?
Anywhere you need to protect the system
For what reason would you use a direct acting relief valve?
Anytime you want to protect your system from damage
For what reason would you use an unloading valve?
For returning pump output at a lower pressure once system pressure has been reached
How do you find force?
Pressure x area
What unit is force in?
Lbs
What unit is pressure in?
Psi
What unit is area in?
Inches squared
What is the 3 types of relief?
Cracking pressure
Full flow
Pressure override
What is the first main valve after the pump in a hydraulic system?
Relief valve
Cylinders are used to create linear motion what are motors used to create?
Rotary motion
When fluid flow increases in a system what happens to the pressure?
Decreases
Hydraulic fluid that have small viscosity variations when heated are said to have good _______?
Viscosity index
Demulsibility is the ability of the fluid to ___________
Eliminate water
What is the ratio of the actual delivery rate of a pump to its displacement called?
Volumetric efficiency
Mechanical shock is controlled in a hydraulic cylinder by means of a/an?
Cushion device
When you first start up a system after you installed a new relief valve what position should the pressure adjustment screw be in?
Turned all the way out
What term is used for the output component of a hydraulic system?
Actuator
What does the term flow rate mean?
The measure of the volume of fluid that passes a point in a given time
What is the purpose of a hydraulic cooler in a hydraulic system?
Keep the oil at an optimum operating temperature
What device is used in a hydraulic cylinder to limit the amount of rod extension and steady the rod within the cylinder?
Stop tube
Why does a cylinder have a lower load capacity when it retracts that when it extends?
It has less surface area to work with
Why must you attach an external drain to a sequence valve?
Prevent valve from locking up under pressure
What is the formula for calculating pressure using pascals law
P=F/A
How is volume of fluid expressed in a hydraulic circuit
Cubic inches
What causes pressure in a hydraulic system?
Resistance to flow
What kind of system transmits and controls power through use of a pressurized fluid within an enclosed circuit
Fluid power system
What are pressure gauges used for?
Aiding in adjusting pressure control valves
Determining forces exerted
Troubleshooting
What are the types of pressure gauges?
Bourdon tube
Schrader gauge
How does a bourdon tube pressure gauge work?
Inner tube straightens under pressure moving the dial
What are the purposes of a loop on a pressure gauge line?
Extra adjustment
Prevent vibration
What fitting should thread sealant be applied to?
Only make side
What are the purposes of thread sealant?
Lubrication
Sealing
What is hunting in terms of pressure gauges?
When the pressure gauge needle bounces back and fourth
Why are some pressure gauges filled with liquid?
To prevent shock loading of the gauge needle
What is a schrader gauge?
Gauge that uses and inlet with a spring that moves an armature attached to a needle
What’s PSIG read?
Psi gauge that already has atmosphere pressure accounted for (14.7)
What does PSIA read?
Psi absolute gauge that does not account for 14.7 atmospheric pressure
What are vacuum gauges typically measured in?
Inch/hg (mercury)
What is the max vacuum gauge reading?
29 inch/HG
What is a compound gauge?
A gauge that reads BOTH vacuum and pressure
What is a duplex gauge?
A gauge that reads 2 systems at the same time
What is a differential gauge?
A gauge that uses two systems to read the difference
What are the 3 types of flow meters?
Typical
Turbine
Transducer
What is a typical flow meter?
A flow meter that uses a tube and indicator
What is a turbine flow meter?
A flow meter consisting of a wheel connected to a counter
What is a gauge snubber?
A filtering mechanism used to prevent surging of gauges
What are the 3 types of gauge snubbers?
Porous
Metering
Threaded
What are the two places gauges can be installed?
In series (in line)
Dead ending
What are the 5 main uses of accumulators?
Emergency supply
Shock absorbing
maintain pressure
Acceleration control
Auxiliary support
What is a poppet?
A type of check valve
What are the two main classes of accumulators?
Gas
Mechanical
What are the two types of mechanical accumulators?
Spring
Weighted
What type of accumulator gives consistent discharge?
Weighted
What are the 3 types of gas accumulators?
Non separated
Piston
Diaphragm/bladder
What type of gas is typically used to charge a gas accumulator?
Nitrogen
Why should air not be used in a gas accumulator?
Oxidation
Corrosion
Deteriorate seals
Fire hazard
Prior to pre loading an accumulator what should you do?
Ensure all oil is discharged
Where should an accumulator be in a hydraulic system.
High up
What is isothermal in terms of accumulators?
When the process is slow enough to allow heat transfer
What is adiabatic in terms of accumulators?
Process is fast enough to retain all the heat
How does true adiabatic discharge happen?
Discharge is started immediately upon fluid reaching the accumulator
What gauge is used at a pumps inlet and how is it typically calibrated to zero
Vaccum
0= 14.7
What reading can be seen on a typical flow meter scale?
Gpm/lpm
What do we use flow meters for?
Check internal leakage
Check pumps volumetic efficiency
What is a conductor in terms of hydraulics?
Anything that carries the fluid
What are the 3 types of conductor lines in hydraulics?
Piping material
Tubing material
Flexible hose material
What is the TYPICAL difference between tubing and piping?
Tubing is typically smaller
When is piping typically the conductor of choice?
Long permanent lines
Large flows
What type of piping is typically used?
Seamless steel (black) pipe with a clean interior
What determines the bursting pressure of a hydraulic line?
Wall thickness
Internal Diameter (ID)
What are the 3 most common piping threads?
NPT (American national pipe taper)
NPS (American national pipe straight)
NPTF (dry seal pipe taper)
Which threads are self sealing?
NPT (American National pipe taper)
NPTF (dry seal pipe taper)
What threads require an O-ring?
NPS (American national pipe straight)
What does schedule number refer to?
Wall thickness of a pipe
What is the number range for schedule numbers?
10-160
What does it mean if a pipe has a larger schedule number?
The wall thickness is greater
In terms of schedule number what changes?
Internal diameter
How is pipe measured?
From outer diameter
What is the advantage of pipe?
Cheap
can withstand a fair amount of physical abuse
What are the disadvantages of pipe?
-Leaks at higher pressure
-Can’t be bent
-Requires more fittings
-If a line is disconnected it must be tightened more than previously
-heavy and bulky
How does the dash number system work?
16 = 1 inch
6 = 3/8 inch
What are the flow control methods?
Meter in
Meter out
Bleed off
What is the “safest” flow control method?
Meter out
What is turbulent flow?
Non uniformed flow of fluid in a hydraulic system
Example sharp bend
What type of pump is typically found in a hydraulic system?
Positive displacement
What are the 3 classes of hydraulic fluid?
Mineral based
Synthetic
Water based
What keeps the bladder in an accumulator?
Poppet (check valve)
What is a static seal?
A seal that neither mating surface is moving
What is a dynamic seal?
A seal where one or both mating surfaces are moving
What are the two types of hydraulic leaks?
Internal
External
In terms of copper tubing is M or K thicker?
K
In terms of copper tubing is M or K thinner?
M
When bending tubing will bends add or take away from a tubes overall length?
Take away
What are the 3 types of proportional flow control valves?
Servo actuated spool type throttle
Flapper nozzle pilot control
Proportional solenoid
What does metering in control?
Amount of fluid going INTO an actuator
What does metering out control?
Amount of fluid going OUT of an actuator
What does a bleed off flow control valve do?
Dumps the pressure out of a system back to the tank
What do flow control valves control?
Speed
What does laminar flow look like?
Consistent moving parallel with the piping (or tubing)
In standard pipe threads what comes in contact first?
The flanks
What is the compression rate of O rings?
40-60%
What are the two types of tubing fittings?
Flared
Compression
What are the two types of flared fittings?
Flared
Ferrule
What are the two types of compression fittings?
Sleeve
O-Ring
What is the angle of a JIC flare?
37 degrees
75 included
Why are leakage paths needed in most components?
Lubrication
What can excessive leakage cause in a hydraulic system?
Pressure loss
What purposes do seals serve?
Make up clearances
Keep contamination out
What type of seal would be best suited for rotating shafts in high pressure applications?
Dynamic
What affect does high temperatures have on the viscosity of oil?
It makes it lower
What are some products produced by oxidation?
Sludge
Foaming
What is a non compensating flow control valve?
Throttle valve that does NOT compensate for any variation in pressure or flow.
What happens if flow or pressure increases through a non compensating flow control valve?
The flow or pressure will also increase through the valve
What is the term of the pressure control valve as it first opens?
Cracking pressure
What would you use to control the pressure in a fluid system?
Pressure control
What type of accumulator will supply the most constant pressure when discharging?
Weighted
What would you use in a fluid system to control the speed of an actuator?
Flow control
What type of pressure control valve would you use to have a motor start after a hydraulic vice has clamped the component?
Sequence valve
When a hydraulically operated unit is preforming erratically what would be the first thing to check?
Fluid level
What type of valve is used in conjunction with an accumulator?
Shuttle valve
What type of valve is used in conjunction with an accumulator used in an emergency or auxiliary circuit providing recovery from a power failure or loss of pumping capability?
Shuttle valve
What component is added to a hydraulic circuit for shock absorption during operation?
Accumulator
What two types of seals are used in hydraulic cylinders?
Positive and non positive
What is the purpose of a pressure control valve?
Provides pressure control in a fluid system
How would you provide controlled drain down of an accumulator?
Operation of the flow control valve to bleed off
What elements in a fluid power system are used to control the speed and force?
Flow and pressure
If a hydraulic cylinder is hammering on retraction what can be done to reduce it?
Adjust cushion
What is used in a hydraulic system to provide emergency recovery in the event of a power failure?
An accumulator and a shuttle valve
Why should you use a strainer instead of a filter on a hydraulic pump inlet
Strainer offers less resistance to flow
