Chapter 10 Flashcards
Name the three control factors produced by the various types of valves in a hydraulic circuit.
System pressure
Directing flow
Flow rate
Controlling the flow rate of fluid entering an actuator controls the _______ of that actuator.
Speed
In hydraulic components, a spool or piston often operates in a precision machined _______ without using seals to prevent leakage between the parts.
Bore
List the three sources of external force that can be used to position control valve elements.
Manual force
Pilot force
Electromagnetic force
If the outlet line of a control valve is subjected to system operating pressure, it must use a(n) ______ drain.
External
Name the three basic uses of springs in the operation of hydraulic control valves.
- Positioning a spool or piston
- establishing maximum pressure in a valve,
- serving as a biasing device in pressure or flow control valves.
The pressure at which a pressure control valve just opens is called the ______ pressure of the valve.
Cracking
Heavy internal springs are used to establish the operating pressure of the ______ -operated type of pressure control valve.
Direct
A compound relief valve commonly makes use of a(n) ______ and a(n) ______ in its operation.
Pilot stage
Balancing piston
A(n) ______ drain must be used with sequence valves since both the initial and secondary sides of the valve are subjected to system pressure at the same time during system operation.
External
Counterbalance and brake valves provide ______ control in hydraulic systems.
Restrained movement
Brake valves are used in some hydraulic motor circuits to prevent ______ loads from turning the motor at a higher-than-desired speed.
Overrunning
An unloading relief valve uses a(n) ______ mechanism to assist in the operation of the balancing piston in the pilot section of the valve.
Plunger
A(n) ______ valve restricts a portion of a hydraulic circuit to a maximum operating pressure that is below the setting of the system relief valve.
Pressure reducing
What are the four general classifications of directional control valves used in a hydraulic system?
- Shut-off valves
- check valves
- three-way valves
- four-way valves.
List the five common types of shut-off valves used in a hydraulic system.
- Globe
- gate
- ball
- spool
- needle
______ valves are used in hydraulic systems as both shut-off and metering devices.
Needle
______ directional control valves are designed for the actuation of rams and single-acting cylinders.
Three way
The ______ directional control valve is generally used in systems with double-acting cylinders or hydraulic motors.
Four way
Which type of the valve named in question 21 allows cylinder extension in one position and cylinder retraction in the second position?
Two position
There are five commonly available center positions for a three-position, four-way directional control valve. List these.
Closed
open
tandem
floating
regenerative.
What are the five general categories of actuation methods used to shift directional control valves?
Self actuation
manual operation
mechanical operation
pilot
What is often used on the ends of the spool in directional control valves to automatically return the valve to the normal or restart position whenever the activation force is removed?
Springs
List the three factors that control the rate of fluid flow through an orifice.
Area of the orifice opening
pressure difference between the inlet and outlet sides of the opening
viscosity of the fluid.
Restrictor-type, noncompensated flow control valves provide a consistent flow rate as long as the load on the system is constant and the ______ of the fluid does not change.
Temperature
- An integral ______ valve is often used with needle valves to allow unrestricted reverse flow around the metering orifice.
Check
A(n) ______ flow divider valve allows pump output to be divided between system subsystems using a preselected ratio.
Proportional
Control valves allow a hydraulic system to produce the type of _______ and level of ______ needed for machine operation.
Motion
Force
What is the primary purpose of pressure control valves in a hydraulic circuit?
Protect the system from excessive pressure
The _______ serves as the holder of all the working elements of the valve.
Valve body
Define fixed orifice
Small holes machined into the valve body
What are two sources of internal force typically used to position control valve elements
Springs
Pilot pressure
Why is it important to remove fluid that leaks into internal clearances and control chambers
Can cause valve to malfunction
When a valve is classified as normally open or closed, it is only in relation to the position of the internal elements when the system is _______.
Shut down
Four basic tasks that fluid pressure perform in the operation and control of a hydraulic system.
Open and close control valve
Remote operation
Define pressure override
Difference between cracking and full flow pressure
What are two basic internal modes of operation for pressure control valves.
Direct operation
Balancing piston
Name the two types of pressure control valves that are used to prevent damage to hydraulic systems in cases where the relief valve fails
Safety valve
Fuses
Safety valves are typically set at a pressure _______ above the setting of the primary system relief valve
25 percent
Multiple operating steps actuated in a preselected order can be obtained in a hydraulic circuit by the use of ______ valves.
Sequence
Describe what is needed to lower a load that is held in position by a counterbalance valve
Use the weight of the load
Unloading pressure control valves are commonly found in hydraulic circuits that use accumulators or _______.
Dual pumps
A pressure reducing valve is normally open and must be _______ drained.
Externally
A ________ valve is used primarily to block fluid flow through a hydraulic system line.
Shut off
A three way directional control valve has four ports. Describe what each port is connected to.
Pump discharge
Motor inlet
Motor outlet
Reservoir inlet
The _______ method of directional control activation uses system pressure, which may be remotely sensed, to shift the valve.
Piloting
Which type of three position, four way directional control valve has a middle position with the pump, reservoir, and actuator ports connected?
Floating center
In some directional control valves, the spool is held in position by a locking device called _______.
Detent
What are the two general operating designs of flow control valves?
Restrictor
Bypass
The simplest of the adjustable, no compensating flow control valves is a ________.
Needle
Two ways to accomplish temperature compensation in a flow control valve.
Sharp edged orifice
Heat sensitive metal rod
During system operation, when actuator pressure requirements are below the cracking pressure of the relief valve, a _______ type flow control valve directs any excess pump output flow directly to the reservoir via a port on the valve.
Bypass
