Accessories, Fluids, and Seals Flashcards
what condition can occur if the inlet strainer on a pump clogs?
Cavitation
under what conditions do you need a heater in the reservoir?
when the temperature is too low to let the oil flow
in addition to transmitting power, what four things must hydraulic fluids do?
Lubricate
Seal
Carry away heat
Flush contaminants
What is the main cause of oxidization in hydraulic fluid?
Heat
List four harmful products of oxidization in hydraulic fluid
gum
varnish
sludge
Acids
How can you keep the contaminants in new oil out of the hydraulic system?
A filter cart
Name three points at which contaminants can get into the hydraulic system
New oil
Breather
Rod seals
what information does the code 18/16/14 give you?
It’s the ISO code for how many particles in a given size
why should use a strainer instead of a filter at the pump inlet??
It has the least amount of resistance to flow
what is the purpose of a bypass on a filter?
So fluid can still flow if the filter is clogged
how can you tell when you need to change a filter?
When it is operating on, bypass on start up
what are the four locations for filters and hydraulic system?
Inlet
Pressure line after pump
Return line
Off-line
which type of filter should you use for the reservoir breather?
3 micron with a moisture trap
Is new oil clean enough to use a hydraulic system or do you have to filter it before you install it?
You need to filter it
what is a major source of built-in contamination?
Tapered thread pipe fittings
what causes generated contamination?
Moving system parts
what three particle sizes are measured for ISO contamination level specifications?
4
6
14
between petroleum-based fluids, and non-petroleum based fluids, which type of fluid requires the highest cleanliness level?
Non-petroleum
Which filter in the system has to be rated at the relief pressure of the system?
The pressure line filter
how can hydraulic fluid that comes in contact with your skin for prolonged periods harm you?
It causes cancer
how can a pinhole hydraulic leak harm you?
It comes out at a very high pressure and can pierce your skin and get into your bloodstream
why should a dynamic seal have some leakage?
To allow for lubrication
What condition must the surfaces of metal to metal seal be in before assembly?
Flat with no scratches
what tightening pattern must you use to avoid distortion when bolting rectangular surfaces together?
Spiral from the centre
How can you determine the correct torque value when you assemble a hydraulic component?
Check the manual
What is the main purpose of a backup ring for an O-ring?
Supports the ring from extrusion
what type of sealant should you use on tapered pipe threads in hydraulics?
liquid sealant (pipe dope)
which should have a tighter, fit a dynamic O-ring, or a static O-ring?
Static O-ring
what type of piston rings should you use when no cylinder creep can be tolerated?
Non-metallic
what is the basic purpose of an accumulator?
Adds fluid when more is needed in the system
name three additional purposes of an accumulator
Dampens pulsations
Absorb shock
Allows for thermal expansion
what safety precaution must you take when there is an accumulator in the system?
Ensure the accumulator is depressurized
name three unloading methods for an accumulator
Manual bleed valve
solenoid bleed valve
vented relief valve
what type of gas must be used in a gas accumulator?
Nitrogen
The precharge should never be less than _____________ of maximum system pressure when the accumulator is empty.
25%
When is the precharge put into an accumulator?
when it is empty
What is the main disadvantage of gas or spring type accumulators?
It cannot maintain constant pressure
name three advantages of spring type accumulator
Compact
Operate in any position
No pre-charge needed
why are air and oxygen not used in gas filled accumulators ?
Can cause explosion if it comes in contact with oil
What is an accumulator?
A vessel that store is pressurized fluid, then adds fluid to the system when fluid is needed
What are backup rings used for?
To stop extrusion of the O-ring
What is the most common type of fluid and hydraulics?
Petroleum based
What type of sealant should you use on tapered pipe threads and hydraulics?
Liquid sealant
What type of gas must be used in a gas accumulator
Nitrogen
why do dynamic seals allow for some leakage
For lubrication
what functions does the hydraulic oil perform other than transmitting power?
Lubricates
Seals
Carries away heat
Flushes contaminants
What are the two major classes of seals used in rotary pumps and what do they do?
static seals seal between stationary parts
Dynamic seals seal between moving parts
What are four harmful products of oxidization in hydraulic fluid?
gum
Varnish
Sludge
Acids
what is the main cause of oxidation in hydraulic fluid
Heat
what does the saturation point mean when referring to hydraulic fluid?
When the fluid cannot hold any more dissolved water
What type of filter should you use on a reservoir?
3 µm filter with a moisture trap
would you use a filter or a strainer at a pump inlet
Strainer
What does the particle code 18/16/13 mean?
you have 18 particles greater than 4 µm
16 greater than 6 µm
And 13 greater than 4 µm
What particle sizes are harmful to hydraulic components
6 to 14 µm
What are the four sources of contamination and hydraulic fluid?
New oil
Built-in
Ingressed
Generated
What style of fittings are used in hydraulics?
JIC
What else do accumulators do other than hold fluid?
absorb shock loads
Even out pulsations
Protect against over pressure from thermal expansion
