Test 2 - Hydraulics Flashcards
Force is measured in units of ______ in the metric system?
- newtons
The mass of an object is ???
- a measure of the amount of matter in it
The density of a fluid is expressed in terms of ???
- specific gravity
The number of pounds of force applied to an area is measured in ???
- psi
When calculating the work done by a hydraulic cylinder, you must know the hydraulic pressure and the piston’s ???
- area and stroke
The theory that states that pressure in a confined liquid is distributed equally throughout the fluid is ???
- pascal’s law
If the force ratio between two different hydraulic pistons is a reducing ratio, the piston velocity ???
- increases
Fluid flow in a hydraulic piping system should be ???
- laminar
Which of the following does NOT cause turbulent flow in hydraulic systems?
- large diameter pipes
Bernoulli’s Principle states that the total energy of a hydraulic fluid is ???
- always constant
The functions of a hydraulic fluid include all of the following EXCEPT ???
- generating heat
The viscosity of a fluid is a measure of its ???
- internal friction
A hydraulic fluid with a viscosity of 150 SSU ______ than one with a viscosity of 275 SSU?
- is less viscous
The term that describes the stability of fluid viscosity when it is heated is ???
- viscosity index
Hydraulic oils used for low-temperature applications should have a ???
- low pour point
The ability of a fluid to maintain lubrication between closely fitted parts under load is determined by its ???
- film strength
What type of reaction occurs when a hydraulic fluid oxidizes?
- chemical
It is estimated that the service life of a hydraulic fluid _____ for each 18 to 20°C increase above 54°C
- is reduced by half
Contamination in a hydraulic system can be best controlled by ???
- good maintenance procedures
Corrosion in a hydraulic system generally is caused by all the following EXCEPT
- cavitation
For a hydraulic fluid to function properly over acceptable periods of time, it must ???
- be kept clean
The performance rating of a strainer is based on its ability to remove _____ from the system
- dirt
The point at which a filter allows contaminants to pass through the medium is called the ???
- maximum allowable pressure drop
The medium in a strainer usually is made of ???
- porous wire mesh
Which of the following is NOT true of a filter in a hydraulic system?
- Its openings gradually increase in size
Which of the following is NOT true of depth filters used in highly contaminated fluid conditions?
- They can be cleaned and reused
Wound-yarn filters are used for heavy contaminant concentrations because they ???
- have good removal ratings
How is the filtration area of paper filter media increased?
- pleating
Surface filter media made from sintered metal powders can be used for high-pressure filtration because of their ???
- large mass
When working on or around a hydraulic system, alway remember that the system may be ???
- pressurized
In order to separate contaminants from hydraulic fluid in the reservoir, the fluid must be ???
- moved slowly
The bottom of a hydraulic fluid reservoir should NOT be ???
- flat
A hydraulic reservoir relies on an interior baffle to ???
- help heat transfer
What method is NOT used to maintain the temperature of hydraulic fluid at an acceptable level?
- using reservoir with thick side walls
Most liquid-cooled heat exchangers transfer heat by means of ???
- separated fluids moving in the opposite direction
For what reason is an air breather installed on a reservoir?
- Prevent pressure buildup
An accumulator is used in a hydraulic system for all of the following EXCEPT to ???
- take the place of the pump
Because of their non-mechanical design, air-bottle accumulators should NOT be used with ???
- high-speed pumps
Which of the following is the correct procedure to use when charging a bladder accumulator?
- Preload gas, then fluid
A distinctive characteristic of a differential-piston accumulator is that is reduces ???
- fluid volume
A hydraulic pump does all of the following EXCEPT ???
- produce the working pressure in the system
Which of the following types of pumps is NOT a positive-displacement pump?
- centrifugal
The volume of delivery of a fixed-displacement pump ???
- can be changed by changing the pump’s speed
The capacity of a pump may be specified in all of the following EXCEPT ???
- pounds per square inch
The efficient operating life of a pump is usually given in terms of ???
- hours
Because of their design, internal gear pumps are limited to applications having ???
- small capacities and low pressures
A vane pump of the unbalanced design can be identified by its ???
- off-center rotor
The vane tips of a vane pump usually are grooved or split to permit all of the following EXCEPT ???
- a larger contact area at the housing
Variable-displacement vane pumps control fluid flow by ???
- shifting the cam ring
Radial-piston pumps generally are designed and manufactured with a ???
- rotating or stationary block
When selecting a hydraulic line, the most important factor to consider is the ???
- fluid flow rate
Resistance to fluid flow in a hydraulic system is increased by ???
- pipe restrictions
Which of the following does NOT contribute to pressure loss in a hydraulic line?
- direction of flow
Hydraulic lines should NOT be made from ???
- galvanized pipe
Steel piping may be used for hydraulic lines under all the following conditions EXCEPT ???
- when the hydraulic lines are short and contain many bends
When tubing is bent, which of the following does NOT apply to the bend?
- it should be formed by hand
Which of the following is a proper procedure for installing hydraulic tubing?
- Support long tubing runs with clamps or hangers
A disadvantage of hoses in hydraulic lines is that they ???
- wear from flexing
Hydraulic hoses should not be used for temperatures above ???
- 450°F
Most hydraulic hoses are rated with a safety factor of ???
- 4
Directional control valves do all of the following EXCEPT ???
- relieve excess pressure
Directional control valves are NOT classified by the number of ???
- pipe threads
Some manually operated two-way valves are NOT suitable for hydraulic service because of their ???
- low pressure ratings
The closing force of a solenoid-operated valve is usually limited to ???
- 15 lbs
The pressure at which a check valve will start to oped is called its ???
- cracking pressure
Spool valves usually are partially balanced because of their ???
- construction
Three-way spool valves are made with three ???
- primary connections
Selector and diverter three-way valves differ in their ???
- internal construction
A three-position, four-way valve is referred to as a ???
- closed crossover valve
Rotary spool valves can be manufactured to operate as all of the following EXCEPT ???
- five-way valves
A pressure-reducing valve is a ???
- normally open two-way valve
What is another term for the maximum pressure of a poppet relief valve?
- set pressure
What is the pressure at the discharge (outlet) of a sequence valve?
- line pressure
A counterbalance valve is usually constructed as a ???
- double poppet
Unloading valves usually are made for _____ operation?
- pilot
Pressure-reducing valves limit pressure ???
- in one part of the system
Hydraulic shock in a system is controlled by a ???
- shock suppressor
The speed of a hydraulic actuator is controlled by what characteristic of the hydraulic system?
- flow
A flow-controlled valve can be positioned to operate in all of the following ways EXCEPT ???
- counterbalance
A pressure-compensation valve senses pressure at the ???
- downstream valve outlet
Hydraulic cylinders convert fluid force into ???
- straight-line motion
In a double-acting cylinder, the thrust is ???
- greater when the piston forces the piston rod out of the cylinder
A double-end rod cylinder has a piston surface area that is ???
- equal on both sides
Which of the following is true of a ram cylinder?
- it usually does not require piston seals
The pistons of a two-piston cylinder always move ???
- independently
The end caps or heads of most industrial hydraulic cylinders are held in place by ???
- tie rods
Cylinders that move heavy thrust loads usually are furnished with ???
- square flanges
To select the proper hydraulic cylinder for use in a existing system, you must know all the following EXCEPT ???
- piston speed
To determine the total cylinder force, you must multiply the load times the acceleration factor and add the ???
- frictional resistance
What is the purpose of the cushioning device used with a hydraulic cylinder?
- prevent mechanical shock
The speed of a hydraulic motor is determined by the fluid’s ???
- flow rate
All hydraulic motors are _____ motors
- positive-displacement
The maximum fluid pressure that a motor can withstand is defined by ???
- its pressure range
The force exerted by a hydraulic motor while operating normally is called ???
- running torque
When a new hydraulic motor is installed in an existing system, its compatibility must be checked against all of the following EXCEPT the ???
- piping material
The service life of a hydraulic motor is given in ???
- hours of operation
The pressure of the hydraulic fluid entering an internal gear motor acts on the ???
- gear teeth
Gear motors frequently are equipped with wear plates to prevent ???
- internal leakage
Which of the following characteristics applies to variable-displacement hydraulic motors?
- high slippage rates
How far can vane-type rotary actuators rotate?
- just under one revolution
