Flashcards in Fluid Power Deck (64)
Draw and label a typical hydraulic system schematic.
Name the components of a hydraulic reservoir.
Clean out cover
Suction, return and drain lines
Oil level gauge
Filters, screens and strainers
What are the five steps for flushing a new hydraulic system?
1) Flush with light rust and oxidation inhibited oil
2) Operate system at maximum flow rate to generate turbulent flow
3) Check filters
4) Refill with operating charge
5) Reach operating temperature
6) Exercise activators
7) Drain and flush non-circulating zones
What are some advantages of oil mist lubrication?
Constant supply of fresh lubricant
Slight pressurization reduces contamination
No moving parts
Alarm systems monitor flow and oil level
Low lubricant consumption
Lower bearing temperatures due to lower internal friction
Prevents moisture intrusion
Name three types of positive displacement pumps.
Rotary (vane, lobe, gear, rotary screw, blower)
Name four sources (not types) of contamination in a hydraulic system.
1) Built into comments
2) Generated during assembly, break-in and operation
3) External ingression
4)Introduced during maintenance
Hydraulic systems generally required fluid to be filtered through ______ to _____ micron filters.
3 to 10 microns
Name three factors that favor hydrodynamic lubrication.
Oil of high enough viscosity
Name four desirable properties of “dielectric” oils commonly used in aerial lift devices (also called cherry pickers or bucket trucks).
Dielectric strength is not a legitimate test for this application and was voted out of the ANSI standards. It is more important for the oil to be clean and dry, to have a high viscosity index, low pour point, good anti-wear performance, and to be non-detergent.
How is it possible to change the flow rate of a pump?
Change the position of the cam ring.
What are good locations for filters and strainers in a hydraulic system?
Pump strainers (coarse filter on end of suction line)
Filter on pump suction line
Fine mesh pressure filter
Return line filter
Name four types of fire resistant hydraulic fluids.
Water-in-oil Invert emulsion
What elastomers are compatible with phosphate ester hydraulic fluids?
Ethylene propylene (EPM, EPMD, EPR)
Pumps work on the principle of ________ volume at suction side and _________ volume at pressure side.
List three disadvantages of water-glycol FR fluids.
1) Can be used only for moderate pressures
2) Incompatible with other fluids
3) Viscosity may increase as water evaporates (Limited viscosity available)
4) Incompatibility with zinc, cadmium, and magnesium
5) Poor corrosion protection (Corrosion problem)
6) Higher maintenance of fluid during service
7) Poor high temperature performance - low viscosity
What is the hydraulic system schematic symbol for a pressure relief valve?
What is the most hydraulic system schematic symbol for two working lines that cross and connect?
What is the hydraulic system schematic symbol for flexible lines?
What is the hydraulic system schematic symbol for a pump?
What is the hydraulic system schematic symbol for a filter or strainer?
Which type of hydraulic pump produces the greatest pressure?
Piston (reciprocating) pumps
Name two types of hydraulic actuators and what type of motion they have.
Cylinders - linear motion
Motors - circular motion
What is the purpose of baffles in a hydraulic reservoir?
It allows the fluid time to cool, de aerate, and to settle out water and dirt.
Most centrifugal pumps have a _________ and a _______ bearing.
Radial and thrust
Name three types of hydraulic pumps?
Name three causes that lead to failure of hydraulic pumps?
Aeration Excessive heat
Cavitation Improper fluid
Contamination Over pressurization
What are the three causes of aeration in hydraulic systems?
Leakage on suction side pump
Oil splashing return line above oil in reservoir
Low oil level – vortex around suction line
Name three types of fire resistant hydraulic fluids?
Which type of hydraulic pump is most tolerant to dirty/contaminated lubricant?