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39 Cards in this Set
- Front
- Back
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When you close down a flow control to reduce the flow from the pump to the actuator, where does the flow from the pump go that does not go to the actuator |
Over the relief valve to the tank |
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What is the purpose of using more than one stack of valves on a multiple station sub-plate |
To control more than one actuator |
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List two advantages of using a cartridge valve assembly |
Compact Fewer leak points |
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Why is the area ratio of slip-in cartridge poppet important |
It determines at what pressure the valve opens |
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What is the spool movement proportional to in a proportional valve |
The electrical input |
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What is the purpose of the notches on proportional valve spool |
Control flow |
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What six devices provide input signals to the amplifier card for a proportional valve |
Joystick Potentiometer Plc Tach generator Pressure transducer Temperature sensor |
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what is the main reason for using a servo valve instead of a proportional valve |
Greater accuracy |
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What is the main maintenance concern with servo valves |
The main concern is meeting the high fluid cleanliness target required for servo valves. This involves removing two micron particles that can jam spool movement |
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List two main advantages of stack valves over externally plumbed valves |
Fewer leak points More compact |
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Which extra function can a proportional directional valve perform? |
Flow control |
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List three advantages of a proportional valve over a servo valve |
They are more dirt tolerant because the parts are fitted with greater clearances They are more rugged They are less expensive |
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What is the spool movement proportional to in a proportional valve |
The electrical input |
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Besides speed, what else can a proportional valve control? |
Acceleration and decelert |
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Which type or proportional valve spool is best for controlling a motor |
A restricted Center spool |
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What is the main function of an amplifier card? |
To increase the input signal to drive the solenoid |
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List four functions that an amplifier card can provide besides increasing the power of a signal |
Dead band compensation Gain setting Dither signal Ramp settings |
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What does the ramp setting control |
Acceleration and deceleration |
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What does the closed inner loop system control on a proportional valve in order to provide more accurate control of the actuator |
The spool position |
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Which device does a proportional valve use to sense the spool’s position |
An LVDT |
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What must you prevent when assembling stack valves |
Make sure that the o-rings are properly seated and the the tie bolts are evenly tightened |
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What does summing junction in an amplifier do |
Compares the actual position with he set position of a spool or actuator and sends an error signal to correct the position |
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What does a closed outer loop system on a proportional valve correct |
Actuator position |
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What is the operating principle of proportional pressure controls |
A proportional solenoid replaces the spring in a conventional pressure control valve to set the pressure |
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List three types of proportional pressure controls |
Nozzle Plate Poppet |
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How are the three types of proportional pressure controls used |
To control the main stage of conventional pressure controls |
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What are the differences between the parts of a servo valve and the parts of a proportional valve |
A servo valve uses a torque motor instead of a proportional solenoid. The servo valve also has an internal mechanical feedback, while a proportional valve does not |
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Which is more accurate, a servo valve or a proportional valve |
A servo valve |
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List three types of servo valves |
Flapper nozzle Jet pipe Staged |
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What does hysteresis indicate |
The accuracy of the valve |
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What is the purpose of keeping the lines from the valve to the actuator as short as possible on servo valves and proportional vavles |
For more accurate control |
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Which stack valve must be installed at the top of the stack |
The directional control |
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Which valve must be installed closest to the supply to the sub-plate in a stack valve assembly |
The relief valve |
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Does a stack valve handle a flow of 50 GPM |
Yes |
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which type of cartridge valve is used or low flows |
Screw in type |
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List two specifications that determine whether a slip-in cartridge valve opens |
Area ratio on the spool The Available pressure at the port |
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What must always be done to a manifold block just received from the machine shop before the cartridge valves are installed |
Clean it out thoroughly |
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If a screw in cartridge fails should you repair it or throw it away |
Throw it away |
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What is the difference between the operation of a conventional solenoid-controlled directional control valve and the operation of a proportional valve |
The conventional valve’s spool shifts all the way to one position or another; a proportional valve can move its spool to an infinite number of positions within its range |
