Hydraulics (HYD Fluid And Vane Pumps Flashcards
What is hydraulic fluid?
The substance used for transmitting energy from the pump actuator in a hydraulics system.
What is lubrication?
The process of reducing friction between relatively moving surfaces which are in contact.
What are the 4 things hydraulic fluid does?
- Transmit Power
- Lubrication
- Cools Moving Parts
- Seals Clearances
What is a fluid film?
The coating of hydraulic fluid which prevents contact between moving parts in a hydraulic system
What is lubricity?
A liquids ability to form a durable fluid film.
What are the 2 factors which relate to lubricity?
- A fluids natural film thickness
- A fluids tendency to adhere to a surface
If hydraulic fluid is cold it _______
Thickens
If hydraulic fluid is warm it ____
Thins
What are 2 primary causes for cavitation?
- Cold hydraulic fluid
- Obstruction of the inlet
What does R&O stand for?
Rust and Oxidation Inhibitor
What are the 3 tests which determine fire resistance of hydraulic fluid?
- Flash point
- Fire point
- Auto ignition point
What is flash point?
Temperature at which vapor for hydraulic fluid ignites, but goes out when flame is removed.
What is fire point?
Temperature at which hydraulic fluid burns continuously.
What is auto ignition temperature?
Temperature at which hydraulic fluid ignites without a flame or spark. (Spontaneous combustion)
What are the 7 steps to set the pressure compensator and relief valve?
- Block flow to system
- Set relief valve to 150PSI
- Run compensator all the way in
- Set relief valve to specified pressure (250 above)
- Set pump compensator to specified pressure
- Lock down jam nuts
- Open flow to circuit
What are the 2 types of fire resistant hydraulic fluids?
- Water Based
- Synthetic
What is water-oil emulsion?
Oil is broken down and encapsulated by water using an emulsifier. Typically 60% water to 40% oil.
What is inverted emulsion?
Water is broken down and encapsulated by oil using an emulsifier. Typically 60% oil to 40% water. (Also known as Morg Oil)
What is a problem with Phosphate Ester?
Corrosion
What are the 2 problems specific to invert emulsion?
- Phase Separation
- Bacteria Formation
What is water glycol?
A water based fire resistant hydraulic fluid which consists of 60% glycol and 40% water. (Since glycol is similar to antifreeze, this works at low temperatures)
How should hydraulic fluid be stored?
Inside. Barrels on the side or with covers to prevent contamination.
Which pumps have a set volume?
Fixed displacement pumps
Which pumps change volume?
Variable displacement pumps
What are required for fixed displacement pumps?
Relief Valve
What is required for variable displacement pumps?
Pressure compensator
Do variable displacement pumps have relief valves?
Yes
What do vanes pumps do?
Generate a pumping action by causing vanes to track along a ring
How do vanes pumps operate?
As the rotor turns, vanes are thrown out. These vanes track along a stationary ring, causing a positive seal.
What are the 3 styles of vanes pumps?
- Unbalanced
- Balanced
- Cartridge
What is the problem with unbalanced vane bearings?
Susceptible to side loading. Require thrust bearing.
How do balanced vane pumps prevent issues associated with unbalanced?
Pressure on both sides of the shaft, preventing thrust load.
What is a cartridge vane pump?
Vane pump in which the vanes and housing are contained in a cartridge assembly, which can be easily replaced.
What must happen before a vane pump can operate properly?
A positive seal must exist between vane tip and cam ring.
Can all hydraulic motors be pumps?
Yes
Can all pumps be hydraulic motors?
No
What must a pump have in order to be used as a hydraulic motor?
High pressure seal.
