Hydralic Princables Flashcards
What does a steering orbital do
Allows for assistance in steering larger vehicles and allows a fixed steering system even if the machine is inoperable
How does a steering orbital spring back into place
Using leaf springs which also create steering resistance
What does open centre mean
It means always working
What is flow
Cause by difference in pressure at 2 points
What is velocity
It is average speed of which particles pass a point
Speed in a given direction
What is flow rate
Volume of liquid passing a point at a given time
What is laminar flow
Flow which is smooth and uninterrupted
What is turbulent flow
Flow which is irrational and causes heat to form
Does pressure drop after an orafice
Yes because the pressure is build up before the orafice, once it passes it drops down
How does Bernulies princable work
As pressure decreases above an object velocity will increase and pull it up
If on a hydraulic schematic an object is in a dotted box what does this mean
It is one component
What does a fluid conditioning device look like on a schematic
It is a square
What does a closed centre drawing look like
All ends are closed off nothing is working
What does an open centre drawing look like
It is like an open goal or a big h all working
What does a tandem drawing look like
It is a crying clown bottom 2 are connected and top 2 are capped off
What does a float centre drawing look like
It is a 4 all are allowed to connect other than the pump therefore making it float
What does a rotary device look like on a schematic
It is a circle
If the arrow points in on a rotary device what does this make it
A motor
What does it mean if there are 2 arrows on a rotary device
It means it is bidirectional
What would be written on a pump rating plate
Max discharge pressure PSI
flow output at max driven speed LPM
and displacement per pump shaft revolution CCM
What does a pump do
Convert mechanical energy into hydraulic energy
What does a hydraulic motor do
Convert hydraulic energy into mechanical energy
What is a positive output pump
A pump which has the same output as input
What is a non positive output pump
It is a pump which can be stalled/ load can overcome the output and output will be slower/ not the same
What is a variable pump
A pump which can change out put
What pump can be fixed and variable
A vane pump
What is an open loop hydraulic circuit
It is from reservoir to reservoir
What is a closed loop system
It has no reservoir the oil is always stuck in one system
What is the minimum volumetric efficacy a pump should be giving out
60 percent
What is a closed centre system
A system which doesn’t drive all the time
What is cavitation
Where demand exceeds supply and small vacuum pockets where molecules split and stretch causing pitting due to lack of oil and formed
What is aeration and how do you find it
It is when air gets into a system causing sponginess , foam and bubbling this can be found by finding the hole using oil and seeing it bubble
What is swash plate cavitation
It is where demand exceeds supply and it runs the plate dry or low on oil causing lack of oil and therefore pitting on components
How do you know how efficient a hydraulic pump is being
Check the rating if the spec is 20 gpm and the pump is giving out 16 it is 80 percent efficient
If it is low check filters and oil to perhaps improve efficacy
What is a pressure control device and what does it do
It limits maximum pressure, provides redirection of pump flow when it must be maintained ( unloading )
It also provides redirection while not maintained ( off loading )
Alternate flow for pressure seqencing
Reduce or step down pressure for a sub circuit
What is an example of a pressure control device
Relif valve / unloding valve / pressure seqencing valve / pressure reducing valve / counter balance valve
What is cracking pressure
It is the pressure needed to overcome the spring to release oil
What is a compound relief valve
2 relif valves in 1 one small one big to allow for surges
What is a sequencing valve
It is a pressure relief valve which allows a next circuit to work after that one has pressurised
What is a pressure reducing device
It is a device which always ensures pressure is correct for a component
What is a counter balance valve
Allows rhe system to be smooth and predictable with unexpected loads, using a solenoid , it is variable
Why would you use nitrogen in an accumulator
Because it is inert and safe
What does an attenuator do
It reduces noise and pulses through a system
What makes a cylinder non differential
It means it can put more force outward than inward due to surface area of cylinder
What is the difference between a ram and cylinder
A ram is bigger than 50 percent of the housing
How would you know a pilot check valve is broken
It will creep as valve should block flow until other is opened
What is drift rate
It is how fast a cylinder will drop if left with load on it
What is cycle time
It is how long it takes for a ram to power out and retract
What is the iso number for hydraulic oil cleanliness
4406
What are 2 simple checks for a hydraulic front loader
Drift rate and cycle time
What way do the arrows face on a oil cooler
Facing out
When referring to a planetary gear transmission how could Infinitely variable gear range be achieved
By adding a hydraulic motor and pump
How is direct drive achieved in a planetary carrier
Locking 2 components together
How is reverse achieved in a planetary gear set
Holding the planetary carrier
What is a hydraulic filter clearance
5 ųm
What is a hydraulic system clearance
5 to 13 microns
What can hydraulic injection cause
Gangrene
What does hydrostatic mean
It is a non mechanical connection
What are priority circuits
It is the circuits which have a ranking order of oil supply
1 is brakes and safety features
2 is suspension
3 is scv less needed stuff
What are 3 types of accumulator
Gas, sprung and weighted
What are the oil pressure ratings
Red is high pressure pink is low
Blue is no pressure
Green is trapped oil
What is the percentage of oil which is air
10 percent
What does flow across an orifice cause
A pressure drop in that area
What does margin pressure refer to on an ls system
It is the pressure range of which the pump can operate
When inspecting a system you notice an o ring has gone slimy and soft what could this suggest
The wrong oil is being used
If a hydraulic ram has been removed and the ram has shown signs of wear on one side what will this suggest
The pivot point is siezed
Constant flow rate into a smaller diameter pipe what happens ?
It will increase velocity
What is created by resistance to flow
Resistance
What does 2 / 3 mean for a hydraulic circuit
2 boxes/ ports and 3 ways for oil to travel
10 um is equal to?
0.001
What is more efficant turbulent flow or laminar
Laminar due to no heat loss / wasted work
What way does the arrows point in on a hydraulic heater
Inward and outward for a cooler
What does it mean if a dotted box surrounds a few parts
It is one component
How can a vane pump be variable
A spring allows the pump to move and go into an idle position
How is a hydraulic schematic shown on of off
Off / neutral
What is the purpose of a pressure control device
Limit max pressure, provide redirection of flow, counterbalance force
Alternate flow for pressure sequences
What is a compound relief valve
It is 2 valves in one one is to keep pressure constant one is for big surges
What is flow control
In theory like a resistor
Limit max speed of actuators
Limit max power available
Proportionally divide pump flow
What determines flow in a hydralics system
Area, orafice shape, restrictions, pressure across orafice, fluid viscosity
What is a check valve
Allows fluid to go one way
What is a check valve
Allows fluid to go one way
What is a priority flow regulator
A series of check valves which aim to go in order of priority
What is a flow divider valve
It is a valve which uses a valve and the side with the lesser flow is combated with spring force causing it to equal out
What do 2 lines above and below the valve mean
It is proportional/ infinite open and close range
What does a single acting ram mean
It is not powered back it powers back with load
What is cylinder cushioning
It is where there are 2 orafices allowing flow to leave the cylinder which slows the flow down as it covers 1 it is forces to slow
What can aeration cause for an operator
Spongey feeling on implements
