Final Flashcards
(87 cards)
1
Q
Advantages of Fluid Power
A
- Easy and accuary of control
- Control can be automated by PLC or microprocessor
- Multiplication of Force
- Very large forces can be generated and reversed quickly
2
Q
Drawbacks of Fluid Power
A
- Hydraulic oil is messy and it will leak
- Conductors not as easy to route as “wires”
- Efficiency
- Hazards to Manage –> Fire, Noise, Hight pressure oil leak
3
Q
Pressure Units
PSI
A
One pound of force applied to one square inch
4
Q
Pressure Units
Pascal
A
The force of one Newton applied to the area of one square meter
5
Q
Definition
Pascal’s Law
A
Pressure applied to a confined liquid is transmitted undiminished in all directions and acts with equal force on all equal areas and at right angles to those areas
6
Q
Pascal’s Law the basis of Hydrostatics
A
The static part implies that the fluid is confined and at rest or nearly so
7
Q
Definiton
Laminar Flow
A
A condition of flow in a passage that’s typified by slow movement of fluid in a relatively straight path along the cneterline of a passage
8
Q
Definition
Turbulent Flow
A
A condition of flow in a passage that is typified by rapid movement of fluid in a passage, where the fluid is churning and bouncing off the passage walls
9
Q
Definition
Meter In
A
To regulate the amount of fluid flow into an actuator or system
10
Q
Definition
Meter Out
A
To regulate the flow of discharge fluid out of an actuator or system
11
Q
Definition
Accumulator
A
A vessel, normally cylindrical, whihc is used to store fluid and gas for future release of the energy in the compressed fluid and gas
12
Q
Schematic
A
Line
Working Main
13
Q
Schematic
A
Pressure Compensated
14
Q
Schematic
A
Reservoir
15
Q
Schematic
A
Vented Reservoir
16
Q
Schematic
A
Hydraulic Pump
Fixed Displacement
17
Q
Schematic
A
Hydraulic Pump
Variable Displacement
18
Q
Schematic
A
Hydraulic Motr
Fixed Displacement
19
Q
Scehmatic
A
Hydraulic Motor
Variable Displacement
20
Q
Schematic
A
Hydraulic Motor
Bi-directional
21
Q
Schematic
A
Single Acting Cylinder
22
Q
Schematic
A
Double Acting Cylinder
23
Q
Schematic
A
Electric Motor
24
Q
Schematic
A
Nonelectric Prime Mover
25
# Scehmatic
Spring Load Accumulator
26
# Schematic
Gas Charged Accumulator
27
# Schematic
Heater
28
# Schematic
Cooler
29
# Schematic
Temperature Controller
30
# Schematic
Filter, Strainer
31
# Schematic
Pressure Gauge
32
# Schematic
Flow Meter
33
# Schematic
Temperature Indicator
34
# Schematic
Direction of shaft rotation
(assume arrow on near side of shaft)
35
# Schematic
Air Bleed
36
# Schematic
Check Valve
37
# Schematic
Pressure Relief
38
# Schematic
Pressure Reducting
(No drain shown)
39
# Schematic
Sequence Valve
40
# Schematic
Counterbalance Valve
41
# Schematic
Unloading Relief Valve
42
# Schematic
Flow Control
Adjustable, Non-compensated
43
# Schematic
2 Position/2 Way Directional Control Valve
44
# Schematic
2 Position/3 Way Directional Control Valve
45
# Schematic
2 Position/4 Way Directional Control Valve
46
# Schematic
3 Position/4 Way Directional Control Valve
47
# Schematic
3 Position/4 Way Directional Control Valve
48
Whats the purpose of an accumulator
- Energy source (supplement pump)
- Emergency Power
- Shock absorption (see on sprayer booms)
- Thermal expansion protection
- Leakage compensation
- Pulsation dampening
49
Types of Contamination
- Solid or Particle
- Heat or Thermal
- Air and Gas
- Water
- Chemical and Radiation
- Microbial Growth
- Built-in
- External
- Intermally Generated
- Maintenance Generated
50
Functions of an Reservoir
- Fluid container
- Cooling
- Allow air to separate out
- Allow debris to settle out
- Provide good inlet conditions to the pump
51
Why a resevoir may need to be pressurized
- High altitude operation
- Pump located above reservoir
- Cold weather start up
52
Benefits of utilizing Cartridge Valves
- Greater design flexibility
- Lower installed cost
- Smaller package size
- Alleviated external leakage
- Easier troubleshooting
- Easier maintenance
- Better organized plumbing
- Lower noise levels
53
# Definition
Relief Valve
A valve that limits the pressure at its inlet port by exhausting flow present at its inlet port to another chamber of lower pressure potential its outlet port
54
# Definition
Unloading Valve
A valve that's normally closed and opens from a separte fluid source on rising pressure thats balanced against a precision spring
55
# Definition
Simple Needle Valve
A two-way valve that may be opened or closed to block the flow of fluid in a passage
56
# Definition
Pressure Reducing Valve
A valve that decreases the downstream pressure (at the valve outlet) to control the flow and therefore the outlet pressure to some present level
57
# Definition
Sequence Valve
A valve that is normally closed or normally open and changes to the opposite state when pilot pressure is applied to its spring chamber at a present pressure level
58
# Definition
Counterbalance Valve
A valve used to balance the weight of a machine or dead load by causing a back pressure in the system cylinders of sufficient magnitude to support the weight
59
# Definition
Pilot Operated Check Valve
A special check valve that may be opened against a check load by applying pilot pressure from a secondary source to open the check to free reverse flow
60
# Definition
Flow Divider
A mechanical device used to divide the fluid in a passage into two or more separate fluid streams
61
# Definition
Flow Meter
An analog device which indicates the volume of fluid passing through its interior passage
62
# Definition
Pressure Gauge
A visual indicator of pressure that is set for "zero" psi at atmospheric pressure and includes a dial which will continue to indicate the level of pressure above atmospheric pressure
63
# Definition
Pressure Compensated Flow Control Valve
A valve used to cause a variable pressure drop in a fluid passage, thus reducing the amount of fluid that may pass through the passage regardless of pressure level at the inlet of the valve
64
# Definition
Directional Control Valve
A valve whose primary function is to direct or prevent flow through selected channels
65
# Definition
Cavitation
A localized gaseous condition within a liquid stream which occurs where the pressure is reduced to the vapor pressure
66
# Definition
Starting Torque
Friction is the resistance to relative motion between two materials in contact with each other
Ex. Grain auger, grain has static to it dont want to stop an auger full of grain
67
# Definition
Entrained Air
Any air present in excess of the saturation level of the fluid at a given pressure
68
Closed Circuit Hydrostatic Transmission
A provision for sensing the motor speed and using this signal to adjust the pump displacement to increase or decrease the motor speed until it reaches the set point
69
Open Circuit Hydrostatic Transmission
No feedback of the motor speed
70
Open Center Circuit
Have a passage designed in the casting that allows all inlet flow when the spool is in the neutral or cenmter position to pass through a bypass area at the low pressure drop
71
What happens to pump system pressure when DCV is active
When all valve spools are in neutral position (no work is being performed) the power consumed by the hydraulic system is at its lowest
72
Closed Center Circuit
Do not have a bypass passage and block all flow through the valve when the spool is in the neutral or center position
73
Standby Condition Closed Center Circuit
Closed center valves are used with variable displacement pumps where system flow in the neutral position **does not** exist as the pump will be in its "cut off" or "standby" position
74
Regenerative Flow
- Pressure is equal on both ends of cylinder
- Cylinder is effectively reduced to rod size
- Speed is increased
- Force capability is reduced
- Only applies in **extension**
75
Draw the concept of pressure override in a pressure relief valve
76
Direct Operated Relief Valve
Where either a ball or a poppet is held in the closed position by an adjustable spring
- This blocks the flow path to the tank
77
Pilot Operated Relief Valve
Used in hydraulic systems where the amont of pressure override is **critical** to protecting components and the hydraulic lines
78
How to achieve Pressure Compensated Flow
Piston or Spool Type
- By using springs to maintain a constant pressure drop across the metering orifice
79
What *limits* the allowable pressure for pressure compensated flow
An input pressure increases, output flow is restricted as either the piston or spool is closed off. This prevents an increase in output flow as the increase of input system pressure tries to force more flow through the valve
80
Simple Orifice
Conveniently be inserted into a hydraulic line as a stand alone valve or more typically into a hydraulic fitting as a means of restricting the flow into a branch circuit
81
Pressure Override
The measure of pressure increase over the nominal setting of a device when additional fluid flow is passed over the device after it initially opens
82
Pressure Intensification
Occurs on the Annular (rod end) side of a double acting cylinder when in "meter out" control
83
When do you see Pressure Intensification
Piston seal failure in meter out control
84
Volumetric Efficiency
A function of clearance spaces, system pressure and pump speed
85
Torque Efficiency
A function of speed and fluid viscosity
86
Temperature Contamination Effects on Hydraulic Fluid
Hydraulic fluid running over 140F effectively doubles the oxidation rate of the hydraulic fluid cutting its useful life in half
87
Causes for Cavitation
- Restrictions in the flow of the hydraulic fluid to the inlet
- Excessively clogged inlet screens or flters
- Running pump too fast
