[Hydraulics] Flashcards
How may both rigid and flexible copper tubing be cut?
Tubing cutter or a hacksaw
What is the compressibility of hydraulic oil?
1/2 of 1% at 1,000 psi
Horsepower requirement for the energy medium used to drive the hydraulic pump in the system
Horsepower of prime mover
Resistance of a fluid to flow within itself
Viscosity
List PSI and diameter for:
1) Threaded piping
2) Welded, flanged-connected piping
1) Diameters up to 1 1/4 inches and pressures up to 1,000 psi
2) Exceeding 1 1/4 and 1,000 psi
Valve that is usually manually-operated and used to stop and start the flow of fluid
Stop valve
Types of filters
- Proportional flow - a portion of system flow passes through filter
- Full flow - all system flow passed through filter
- Indicator type - flow filter that tells you when filter is getting dirty
Anything which tends to produce or modify motion
Force (push or pull)
Types of piston pumps
Axial (swash plate) and radial
Swash plate - main shaft is connected to it; also called a tilt box; by varying the angle of the swash plate, we will be able to vary the discharge of the pump
Which type of line is generally used for its resistance to vibration?
Flexible hosing
Troubleshooting rules
- Find out as much about the problem as possible
* Never disassemble a component unless you are sure it is at fault
Pressure reading that does not take into account atmospheric pressure
Pounds per Square Inch Gauge (PSIG)
Perpendicular distance from the fluid level on the reservoir to the pump
Lift
Seven things about preventative maintenance
- Follow PMCS schedule
- DIRT is #1 enemy of a hydraulic system
- Change or clean filters and strainers as required
- Keep the environment clean
- Always filter the fluid before you fill the reservoir
- Visual inspection can be performed
Device in the fluid line used to trap contaminates from the fluid flowing through them
Strainers
1) Condition where entrapped air is pulled out of the fluid and erodes port materials
2) How is it caused?
1) Cavitation
2) Too high of an inlet line or inlet vacuum
Define types and sizes of copper tubing
Type K - heavy wall (hard and soft)
Type L - medium wall (hard and soft)
Type M - thin wall (only hard)
What kind of line is used in hot and cold water distribution systems and hot water heating systems?
Copper tubing
System in which return oil from the actuator is directed to the reservoir to be picked up by the pump and recirculated
Open loop system
Two types of pipe benders
- Internal - used when both ends flared
* External - used when one end flared
Rotary thrust or turning force of a motor, engine, or wrench
Torque
Law that states “Pressure applied to a confined fluid is transmitted undiminished, and in all directions, and acts with equal force on equal areas and at right angles to them.”
Pascal’s Law
What are the two types of tubing used for hydraulic lines?
Seamless and electric-welded
1) The ability or capacity to do work
2) What are its two forms?
1) Energy
2) Potential energy (pressure) and kinetic energy (flow)
Pressure reading that is equal to gauge pressure plus atmospheric pressure
Pounds per Square Inch Absolute (PSIA)
What stores high pressure for future use? Used in hydrostatic systems to develop flow; most common is gas-charged (dry nitrogen)
Accumulator before working on a circuit, make sure all pressure is relieved (hydraulic only)
Types of bourdon tube gauges
- Simplex - designed only for reading pressure
- Duplex - measures two different pressure at the same time and both are reading on the same scale
- Compound - designed to measure pressure and vacuum
- Vacuum - designed to only measure vacuum
1) Simple relief valve
2) Compound relief valve
1) High override pressure (bad)
2) Low override pressure (good)
Force applied to a unit area; resistance to flow
Pressure
What is gained in force is..
lost in distance
Condition where air is entering the inlet side of a pump
Aeration
Perpendicular distance from the pump discharge to the highest point in the discharge line
Head
Law that states “Energy can neither be created nor destroyed”
Law of energy conservation
How are strainers and filters rated?
- Strainers - rated in mesh
* Filters - rated in microns
What are the three pressures associated with pressure relief valves?
Cracking, full flow, and override pressure
List type of linear actuators
Single-acting
Double-acting
• Differential
• Non-differential
Types of vane pumps
Unbalanced, unbalanced variable displacement, and balanced
Converts mechanical energy to hydraulic energy
Hydraulic pump
Basic requirements of circulatory system
- Lines
- Terminal fittings
- Supports
- Lines with smooth interiors
- Kept clean from all sources of contamination
Valve used for quick opening and closing
- Plug valve
* Butterfly valve never paint
Three major groups for troubleshooting
• Energy group
- prime movers
- electrical source
- internal combustion engines
• Mechanical group
- check couplings for looseness or damage
- check for binding linkages
• Fluid group
- LEAKS are the most common source of trouble
- internal leaks cause losses in efficiency
- external leaks are fire and safety hazards
Amount of space occupied in three dimensions
Volume
Temperature at which a fluid’s vapors will ignite
Flashpoint
Valve used to protect the system from overloading
Relief valve
Types of hydraulic fluids
- Petroleum base
* Synthetic fire resistant
Measurement of a bounded region or plane, or the surface of a solid
Area
System in which the fluid discharged from the actuator is recirculated at low pressure back to the pump inlet instead of being returned to the tank
Closed loop system
What are the three types of lines in liquid-powered systems?
Pipes, tubing, and flexible hoses
What are the two types of fittings?
- Solder - used with either rigid or flexible copper tubing
- Compression (flared) - used only with flexible copper tubing; principle use is in air piping and fuel-oil lines for their vibration resistance
Device which synchronizes two identical cylinders’ speed regardless of load balance between them
Flow divider
What is the greatest aid to troubleshooting?
Confidence in knowing your system
What are the normal and maximum operating percentages?
- Maximum normal is 50%
* Maximum is 75%
The rate of doing work or expending energy
Power
Any force which stops or retards the movement of a body
Resistance
Exerting a force through a definite distance
Work
Volume of liquid that can pass through a pump, motor, or cylinder in one revolution
Displacement
Types of gear pumps
External gear: spur, helical, and herringbone
Internal gear: gerotor (ring gear)
Positive displacement pump whose output cannot be made variable
Fixed displacement pump
How are pumps rated?
- Flow in GPM
- Maximum Operating Pressure (MOP)
- Given drive speed
Valve with long tapered needle and seat
Needle valve never over-tighten
Converts hydraulic energy to mechanical energy
Actuator
Pump that delivers a set quantity of fluid for each revolution or stroke
Positive displacement pump (hydrostatic)
Positive displacement pump whose output can be changed to suit operating conditions
Variable displacement pumps
Where are the strainers and filters in relation to the pumps?
Strainers are before pumps and filters are after pumps
Device in the fluid line used to trap fine particles and prevent them from remaining in the system
Filter
Device that is used to create flow by using an outside source of power (prime mover)
Pump
Amount of liquid flow that a pump will produce in a given time
Delivery
Function of confined fluids
Transmit power (liquid pressure) Multiply force (liquid pressure) Modify motion (liquid flow)
Describe the two types of flow
Laminar: a smooth, parallel flow path with fluid particles traveling in a straight line, undisturbed
Turbulent: Upset, erratic flow path with fluid particles colliding with each other
Valve used for straight lines of flow; has either rising stem or non-rising stem, and is difficult to repair
Gate valve
List the two mechanical and soldering techniques
- Single flare - 45 degree flare on end of tubing
* Double flare - 45 degree flare on end of tubing which is doubled over
Lightweight unit you can use to check or troubleshoot a hydraulic-powered system on the job or in a maintenance shop
Portable hydraulic-circuit tester
Valve used to direct the flow of fluid to a specific point or component
Directional control valve
