Hydraulics Systems Flashcards
_____ relates to the use of confined fluids to transmit power, multiplying force and modifying motions.
Hydraulics
Hydraulics is based upon a principle discovered by the french scientist _______ in the 17th century.
Blaise Pascal
Hydraulics is widely used in the CG to perform various functions, including the following:
- Steering systems
- Booms/cranes
- Winches and other deck machinery
- Hydraulic presses
- Fin stabilizer systems
- Controller pitch propellars
Pressure applied to a confined fluid is transmitted undiminshed in all directions and acts equal force on equal areas and at right angles to them.
Pascal’s Law
Within Pascal’s Law are found the 3 areas of Hydraulics:
- Pressure
- Force
- Area
Use the following 3 formulas when working with hydraulic systems:
- Force = Pressure X Area
- Pressure = Force / Area
- Area = Force / Pressure
______ is defined as the measure of a bounded region or plane.
Area
______ is expressed in inches square (in2)
Area
________ is defined as anything which tends to produce or modify motion.
Force
_______ can push, pull or rotate and is usually expressed in units of weight. In hydraulics it is expressed in pounds (#, lbs.).
Force
______ is defined as force per unit area and is measured in pounds per square inch (psi).
Pressure
________ is created by resistance to flow, either by force (load) or restricting flow.
Pressure
Inside a Hydraulic Cylinder there are two working surface areas?
The 1st is the cap end** and the 2nd is the **net area.
Hydraulic pressure working on the ______ area forces the piston rod to extend.
Cap End
Hydraulic forces working on the _____ area forces the piston to retract.
Net
With the same pressures, the hydraulic cylinder produces greater force _________.
extending than retracting
What is the formula to calculate the cap end area of a hydraulic cylinder?
Area = D squared X .7854
(D = Diameter in inches)
Formula to calculate the piston area when the force and pressure are known.
Area = Force / Pressure
To calculate the amount of force being applied, multiply the pressure by the cylinder’s area. For extending use the cap area. For retracting use the net area. What is the formula?
Force = Pressure X Area
Calculating force for extension:
Extending
F = P X A
F = 200 psi X 6 in squared
F = 1200 lbs
Calculating force for retraction:
Retracting
F = P X A
F = 200 psi X 4 in squared
F = 800 lbs
Calculating maximum force:
Extending
F = P X A
F = 2500 psi X 8 in squared
F = 20,000 lbs
Calculating maximum retraction:
Retracting
F = P X A
F = 2500 psi X 4 in squared
F = 10,000 lbs
What is the formula to calculate area?
Area = Force / Pressure
Calculate the piston area when force and pressure are known.
Area
Area = Force / Pressure
A = 2000 lb / 500 psi
A = 4 in squared
To calculate the system’s pressure while moving a load, the force and the cylinder’s area must be known. What is the formula?
Pressure = Force / Area
Calculate cylinder pressure extending:
Extending
P = F / A
P = 1500 lbs / 10 in squared
P = 150 psi
Calculate cylinder pressure retracting:
Retracting
P = F / A
P = 1500 lbs / 5 in squared
P = 300 psi
When calculating the movement and force on a cylinder with pressure on both sides of the cylinder, the force exerted in each direction calculated first. Then subtract the force retracting from the force extending. View example of a differential pressure formula:
Force extending = Pressure X Area
Force retracting = Pressure X Area
Force extending = 500 psi X 4 in squared = 2000 lbs
Force retracting = 500 psi X 2 in squared = 1000 lbs
2000 lbs - 1000 lbs = Differential Pressure 1000 lbs
_____ is the ability or capacity to do work.
Energy
Also referred to as STORED ENERGY, _______ is present in a hydraulic system in the form of a FLUID PRESSURE.
Potiential Energy
Also referred to as ENERGY IN MOTION, ______ is present in a hydraulic system in the form of FLUID FLOW, represented by a MOVING ACUATOR.
Kinetic Energy
__________ states “Energy can neither be created, nor destroyed, but instead will simply be changed from one form to another”
The Law of Conservation of Energy
_________ energy changes into _______energy as speed is lost-what is gained in one energy form is lost in another.
Kinetic Energy changes into Potential Energy
_______ is defined as exerting force through a defined distance. In other words, how much effort is exerted moving something a certain distance.
Work
Formula: Work = Force X Distance
One way to express work is in foot pounds
_______ is the rate of doing work. An object is moved a fixed distance either slowly or quickly.
Power
Formula: Power = Force X Distance
Time
The faster an object moves over a fixed distance, the more power is required.
Formula for Horse Power:
1 HP = 100 lbs X 330 ft
1 minute
In hydraulics, ___________ are used to determine horsepower.
Fluid Flow and Pressure
What is the best protection against unsafe practices when working with hydraulic systems?
Common sense and knowledge of the system
Where would you find the following components:
- Reservior
- Pump
- Control valves
- Motors (rotary actuators)
- Cylinders (linear actuators)
- Accumulator
- Filters and Strainers
- Fluid conductors and seals
- Hydraulic fluid
Components of a hydraulic system
When a hydraulic system is operating incorrectly, the cause is generally traced to one of the following:
- Contaminated hydraulic fluid
- Wrong hydraulic fluid viscosity or type
- Insufficient fluid in system
- Air in the system
- Damage
- leakage
These causes result in a problem with one or more of the following fundamental elements of the system:
- Flow
- Pressure
- Direction of flow
A problem with flow, pressure and direction of flow may cause one or more of the following symptoms to appear in the system:
- Excessive heat
- Excessive noise
- Faulty operation
- Incorrect flow
- Leaks
- Vibration
The tools most commonly used in the CG for troubleshooting hydraulic systems are:
- Pressure Gauges
- Flowmeters
- Manufactures tech manual
Most common cause of failures, especially repeated failures in the same piece of equipment, is fluid ______.
Fluid Contamination
_______, which can cause fluid contamination, is another possible cause of failure in a hydraulic system.
Heat
When using a flowmeter, direct the return fluid to the _________.
Reservior
The fluid used in hydraulic systems has four functions:
- Transmit power
- Cool
- Seal
- Lubricate
In order for hydraulic fluid to perform these functions, verify it is the correct type, viscosity and free of contaminants.
_______ is the most important factor in keeping hydraulic systems operating properly.
Contamination Control
Dirt, sand, gasket/sealing materials, component wear particles or any solids within the hydraulic fluid.
Solid or particle contamination
The most common Liquid Contaminant in CG hydraulic systems is ______.
Water
Any dissolved or free air or other gases in the fluid. It causes increased oxidation and reduced lubrication.
Air and gas contamination
Chemical, solvent and microbial growth and any other type of contaminants.
Other Contaminants
Fluid storage inspection and testing are detailed in ____.
NSTM, Chapter 556, Section 5
For petroleum base fluids, such as _______ and ______ fluids, water content is less than 100 ppm is desirable.
MIL-L-17331 and MIL-H-17672 fluids
Maximum allowable water content for MIL-L-17331 and MIL-H-17672 fluids is _____ ppm for any sample.
500 ppm
________ fluids are somewhat hygroscopic (absorb water) with a maximum water content of 3000 ppm (0.30 percent).
MIL-H-19457
For water emulsifying petroleum base fluids, a maximum water content of _______ is allowed.
20,000 (2.0 percent)
_____________ is a water emulsifying fluid and in an emergency, is authorized for continued use at 100,000 ppm (10 percent) by TYCOM/NAVSEA.
Houghton PR 1192
Detailed procedures for handling water contaminated hydraulic systems are found in _______.
NSTM, Chapter 556, Section 8.7
Remove water from hydraulic fluid using several different methods?
- Drain and fill
- Settling and draining
- Centrifuging
- Evaporation
- Filtration
- Water absorbent filters
________ convert mechanical energy from a prime mover, into hydraulic energy(pressure). This energy is used to operate an actuator.
Hydraulic Pumps
Name two broad categories of Pumps:
- Positive Displacement
- Nonpositive Displacement
Nonpositive displacement pumps are not used in hydraulic systems
Positive displacement pumps include the following types:
- Gear
- Vane
- Piston
________ is the quantity of fluid that passes through a pump in one revolution, stroke or cycle, expressed in cubic inches.
Displacement
Output of the pump is considered “_______” because it is not significantly affected by resistance to flow.
Positive Displacement
Most pump failures are attributed to one or more of the following:
- Cavitation 10 - 12% frequency
- Aeration 10 - 12% frequency
- Contamination 80% frequency
- Excessive heat 2 - 5% frequency
- Overpressurization 5 - 6% frequency
- Improper fluid 2 - 5% frequency
_______ occur when pump inlet vacuum get high enough to pull entrapped air out of the hydraulic fluid.
Cavitations
Cavitations occur with as little as ______.
5 inches Hg
_______ is when air enters the fluid on the suction side of the pump.
Aeration
Parts affected by contamination in a Vane Pump:
- Vane tip to cam ring
- Rotor to side plate
- Vane-to-vane slot
Parts affected by contamination in a Gear Pump:
- Tooth to housing
- Tooth to tooth
- Gear to side plate
Parts affected by contamination in a Piston Pump:
- Shoe to swash plate
- Cylinder block to valve plate
- Piston to cylinder bore
Name two types of rotary actuators.
- Hydraulic Motor
- Rotary Actuator
Provides continuous rotation motion.
Hydraulic Motor
Has a limited turning motion of less than 360 degrees. A hydraulic motor converts hydraulic energy into mechanical energy.
Rotary Actuator
Types of motors
- Gear motors
- Vane motors
- Piston motors
_________ is used on motors to help prevent the prime mover from overloading.
Pressure Compensation
Breakage of a motors output shaft is caused by either:
- Shaft misalignment
- Loads with excessive torque
What?
- Stores the hydraulic fluid not currently being used in the system
- Allows space for expansion/contraction of the systems volume due to thermal changes
- Allows gauges to expel from hydraulic fluid
- Allows foreign matter to settle out from the hydraulic fluid
- Allows heat to dissipate from hydraulic fluid
A Hydraulic Resevior
A _______ is a type of actuator.
Hydraulic Cylinder
It converts fluid power into mechanical force and linear (straight line) motion.
Hydraulic Cylinder
The components of a hydraulic cylinder that require the most attention are the _______.
Seals and Pivots
The two most common locations for seal failure with a hydraulic cylinder are the _____.
Rod and Piston Seals
In a _______, the pressure in the net end is greater than in the cap end when extending the cylinder.
meter-out circuit
Control valves are divided into the following categories:
- Flow control valves
- Directional control valves
- Pressure control valves
Regulates flow of fluid
Flow control valves
Controls the driection of flow
Directional control valves
Limits or reduces fluid pressure to:
- relief valves
- pressure reducing valves
- pressure sequence valves
- unloading valves
Pressure control valves
- no pressure
- low or erractic pressure
- variations in flow
- excessive noise or chatter
- overheating system
- permature movement to second operation
- pump fails to unload completely
- faulty or incomplete shifting
- cylinder creeps or drifts
- overheating hydraulic fluid
What do these symtoms indicate when troubleshooting a hydraulic system?
One or more Valves may be at fault
_________ are furnished in matched sets and are not available for individual replacement.
Directional control valve spools
When repairing directional control valves, inspect the valve spools and bores for _____ and _____.
Burrs and Scoring
The directional control valve spools become coated with impurites from the ________.
Hydraulic fluid
When scoring or coating on a directional control valve is not deep enough to cause a leakage problem, polish the surface with ______.
Crocus Cloth
Renew the directional control valve’s body and spool if __________ is excessive.
Scoring or Coating
If a directional control valve’s action was erractic or sticky before removal, it may be unbalanced because of wear on the spools or body.
Renew the valve
If system checks indicate low pressure, check for a weak relief-valve spring using a _____.
Spring Tester
Each ______ is stamped with number, a pressure limit and the date of manufacture. Use this code when testing the cartridges.
Relief Valve’s Cartridge
Test a valve’s cartridge for correct pressure setting by installing in a system and operating the system until you reach the valve’s ________.
Operating Pressure
Three main types of accumulators are:
- Spring loaded
- Weight loaded
- Gas charged
What kind of accumulator is used most in CG hydraulic systems?
Gas Charged
What two components of a hydraulic system are designed to reduce or eliminate certain types of contamination?
Filters and Strainers
Properly functioning _______ are essential to a properly functioning hydraulic system.
Filters and Strainers
_________ are devices whose primary function is the retention, by some porous medium, of insoluble contaminants from a liquid.
Filters
________ are more course than filters, meaning larger particles will pass through.
Strainer
_________ are normally rated in wire mesh numbers.
Strainers
________ are normally cleanable, where filters are not.
Strainers
_________ are most commonly located on the inlet or suction side of the hydraulic pump,but can be found elsewhere, such as resevior fill port or vent.
Strainers
Common places filter are located on a hydraulic system:
- In the pressure line just after the pump
- In return line before entering the resevior
- Before or in a component, kidney or bypass loop
- Offline-a separate pump & filter or a portable filtering unit.
Filters are located in:
- reseviors
- pressure lines
- return lines
_________ are classified as full flow or proportional flow.
Filters
In ________, all the fluid passes through a filtering element.
Full-Flow Filter
In a ___________, only a portion of the fluid passes through a filtering element during each cycle.
Proportional Flow Filter
Filter elements can generally be classified into two groups:
- Surface Type Element
- Depth Type Element
In this type of element, the fluid stream has a straight flow path through the element and contaminants are trapped on the surface of the element.
Surface Type Element
In this type of element, the fluid stream is forced to pass through a multiple layer element and the multiple layers trap the contaminants.
Depth Type Element
_______ are usually constructed of a fine metal mesh with pores larger than 50 microns.
Strainers
_____ are most commonly installed on pump inlet lines inside the reservoir.
Strainers
Two common types of strainers used in hydraulic systems are:
- Wire Mesh
- Edge Disk
A strainer that consist of several layers of wire mesh.
Wire Mesh Strainer
A strainer that consist of a stack of metallic disk, separated by metallic spacers.
Edge Disk Strainer
The contaminants which are accumulated on the strainer are cleaned off using one of the following cleaning devices:
- Edge Wound Type
- Edge Disk Type
Indications that the pump inlet strainer is clogged:
- Pump noise caused by cavitation
- High vacuum pressure at the inlet side of the pump
What are a few ways to tell that pressure differential has beem reached and the filter element is clogged and needs replacement?
- Pressure Guages
- Mechanicla and Electrical Indicators
- Bypass Valve Indicator