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Hydraulics Chapter 10
Terms in this set (69)
Control valves allow a hydraulic system to produce the type of _____________ and level of ____________ needed for machine operation.
To protect the overall system from damage from excessive pressure build up by limiting maximum operating pressure.
What is the primary purpose of pressure control valves in a hydraulic circuit?
The____________ serves as the holder of all the working elements of the valve.
It is a small hole machined into the valve body of a piece of metal stock inserted into the valve body.
Define fixed orifice.
Springs and pilot pressure
What are the two sources of internal force typically used to position control valve elements?
Internal leakage can cause a valve to malfunction
Why is it important to remove fluid that leaks into internal clearances and control chambers?
When a valve is classified as normally open or normally closed, it is only in relation to the position of the internal elements when the system is __________________.
1. Opening a control valve to limit the maximum pressure in a system.
2. Closing a control valve to provide a reduced pressure in a small part of a system.
3. Remotely operating a control valve to promote effective operation to increased operator safety.
4. Operating a compensating device to provide a source of uniform fluid flow.
List four basic tasks that fluid pressure performs in the operation and control of a hydraulic system.
Fluid pressure acting on the surfaces of the internal components of pressure control valves is a key factor in the operation of a hydraulic system.
Define pressure override.
Direct operation and balancing-piston operation
What are the two basic internal modes of operation for pressure control valves?
Safety valve and hydraulic fuse
Name the two types of pressure control valves that are used to prevent damage to hydraulic systems in cases where the system relief valve fails, causing excessive system pressure.
Describe the primary function of the metering orifice in the pilot section of a compound relief valve.
Safety valves are typically set at a pressure____________ above the setting of the primary system relief valve.
Multiple operating steps actuated in a preselected order can be obtained in a hydraulic circuit by the use of _____________ valves.
The system pump needs to be operating with the directional control valve.
Describe what is needed to lower a load that is held in position by a counterbalance valve.
Unloading pressure control valves are commonly found in hydraulic circuits that use accumulators or___________.
A pressure-reducing valve is normally open and must be _______________ drained.
A(n)_____________ valve is used primarily to block fluid flow through a hydraulic system line.
____________ valves may be adjusted from the fully open position to the fully closed position by turning the control handle only 90 degrees.
Allowing free flow of fluid through a line in one direction, while preventing reverse flow in that line.
What is the most common application of a check valve in a hydraulic system?
Connections to the system pump, one port of the cylinder, and a system line leading to the reservoir.
A three-way directional control valve has 3 ports. Describe what each port is connected to in the system.
Have 4 external ports with connections to the system pump, inlet and outlet lines of the actuator, and a system line leading to the reservoir.
A four way directional control valve has four ports. Describe what each port is connected to in the system.
The middle position in a three-position, four way directional control valve is often called the _________________ position. It provides a control feature beyond cylinder extension and retraction.
Which type of a three-position, four-way directional control valve has a middle position with the pump, reservoir, and actuator ports connected?
The____________ method of directional control activation uses system pressure, which may be remotely sensed, to shift the valve.
In some directional control valves, the spool is held in a selected position by a locking device called a(n)___________.
Restrictor and Bypass Control
What are the two general operating designs of flow control valves?
In an operating fluid power system, the _______________ of the fluid will change as the operating temperature of the system changes.
The simplest of the adjustable, non-compensated flow control valves is a_________________.
Contains a mechanism that maintains a constant pressure difference between the inlet and outlet passage ways.
What is a pressure compensator?
1. Specially designed, sharp-edged orifice
2. Heat-sensitive metal rod for the automatic adjustment of the opening in an orifice.
Identify the two ways to accomplish temperature compensation in a flow control valve.
During system operation, when actuator pressure requirements are below the cracking pressure of the relief valve, a(n)______________- type flow control valve directs any excess pump output flow directly to the reservoir via a port on the valve.
1. Be pressurized
2. Effectively deliver fluid to another system branch
3. Accommodate reverse fluid flow.
List three limitations that must be observed when incorporating most bypass-type flow control valves into hydraulic systems.
Proportional flow divider valves are available with a ratio of 50-50 to as high as_______________.
An accumulator permits___________ to be absorbed and strored in a hydraulic system.
Controlling the flow rate of fluid entering and actuator controls the ____ of that actuator.
Sensing/Controlling System Pressure
Directing Fluid Flow
Controlling Fluid Flow Rate
Name the three control factors produced by the various types of valves in a hydraulic circuit.
In hydraulic components, a spool or piston often operates in a precision-machined
____________ without using seals to prevent leakage between the parts.
Mechanical Force, Pilot Pressure, Electromagnets
List the 3 sources of external force that can be used to position control valve elements.
If the outlet line of a control valve is subjected to system operating pressure, it must use an ___________ drain.
Moving the spool of a directional control valve
Establishing the max pressure
Serving as a biasing device in pressure compensating control valves
Name the three basic uses of springs in the operation of hydraulic control valves.
The pressure at which a pressure control valve just opens is called the ____________ pressure.
Heavy internal springs are used to establish the operating pressure of the ____________-operated type of pressure control valve.
Pilot Stage, Balancing Piston
A compound relief valve commonly makes use of a _________________ and a _______________________ in its operation.
Safety devices that do not reseat after discharge
Describe a hydraulic pressure fuse.
An ______________ 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.
Counterbalance and brake valves provide ________________ control in hydraulic systems.
Brake valves are used in some hydraulic motor circuits to prevent ___________ loads from turning the motor at a higher than desired speed.
An unloading relief valve uses a ___________ mechanism to assist in the operation of the balancing piston in the pilot section of the valve.
A _______________ valve restricts a portion of a hydraulic circuit to a maximum operating pressure that is below the setting of the system relief valve.
3-Way Valves, 4-Way Valves
What are the 4 general classifications of directional control valves used in a hydraulic system?
Globe Valves, Gate Valves, Ball Valves, Spool Valves, Needle Valves
List the 5 common types of shutoff valves used in a hydraulic system.
______________ valves are used in hydraulic systems as both shutoff and metering devices.
Restriction check valves allow restricted flow through a line in one direction while allowing _____________ flow in the reverse direction.
______________ directional control valves are designed for the actuation of rams and single-acting cylinders.
The __________ directional control valve is generally used in systems with double-acting cylinders of hydraulic motors.
Which type of the valve named in question 21 allows cylinder extension in one position and cylinder retraction in the second position?
What are the 5 commonly available center positions for a three-position, four-way, directional control valve?
Fluid Flow Actuation
What are the five general categories of actuation methods used to shift directional control valves?
Linear Electric Motor
Describe a solenoid.
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?
Viscosity of Fluid
Area of Orifice
Pressure Difference Between Inlet and Outlet
List the three factors that control the rate of fluid flow through an orifice.
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.
An integral __________ valve is often used with needle valves to allow unrestricted reverse flow around the metering orifice.
Slides the spool of the compensating device to allow full flow
What is a biasing spring, as related to a pressure compensator?
Sharp Edge Orifice
Heat Sensitive Metal Rod
Name two common methods used in temperature-compensated flow control valves to maintain constant flow as the temperature of the system fluid varies.
3 port full flow control valve
Bypass flow control valves are often referred to as ______________ because of their additional port.
Flow divider valves are flow control valves that divide one fluid supply between how many circuit branches or subsystems?
A _____________ flow divider valve allows pump output to be divided between system subsystems using a preselected ratio.
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