Hydraulic Valves

Question 1

What is a hydrostat?

Answer 1

A pressure compensated flow control

Question 2

What are the three types of servo valves?

Answer 2

flapper nozzle
Jet pipe
Staging spool

Question 3

What are four ways to unload a pump?

Answer 3

vent the relief
Unloading relief valve
On off valve
Pilot operated unloading valve

Question 4

What is the purpose of a pilot to open check valve?

Answer 4

Valve can be opened by a pilot to allow flow in the opposite direction

Question 5

What are the three types of pressure controls in a proportional valve?

Answer 5

nozzle
Plate
Poppet

Question 6

where are brake valves used and what do they do?

Answer 6

They are used on the discharge from hydraulic motors.

They prevent over speeding and excessive pressure buildup when stopping or slowing down a load

Question 7

what are transducers?

Answer 7

Sensors that measure position, pressure or velocity

Question 8

what are the two main components of a servo valve?

Answer 8

Torque motor
Spool valve

Question 9

What is a servo valve?

Answer 9

A directional or flow control valve with an internal feedback mechanism built into the valve

Question 10

what is a proportional valve?

Answer 10

A solenoid operated valve that uses a proportional solenoid

Question 11

What are the five types of pressure control valves?

Answer 11

Relief valves, pressure, reducing valves, sequence valves, counterbalance valves, and brake valves

Question 12

what is the purpose of an amplifier card?

Answer 12

To increase the signal from the pilot device

Question 13

What can proportional valves be used for?

Answer 13

to stop an actuator at any point in its stroke.

Control the speed of an actuator.

Control the acceleration and acceleration of an actuator.

Question 14

What is a dead band compensator

Answer 14

It briefly boost the power to make the spool jump across the overlap distance between ports

Question 15

what is gain?

Answer 15

The number of times the output voltage is greater than the input voltage

Output/input

Question 16

What is hysteresis?

Answer 16

A term used to express how accurately the spool moves compared to the input current

Question 17

what is dither?

Answer 17

A small high frequency, alternating current applied to the solenoid to prevent the spool from getting hung up/stuck

Question 18

what is the purpose of an overspeed control?

Answer 18

It prevents a sudden Russia fluid through the flow control when the directional control is suddenly opened

Question 19

what is the purpose of a pilot to close check valve?

Answer 19

Valve is held open by a spring and closed by a pilot to prevent reverse flow

Question 20

what are the four control functions in an amplifier card?

Answer 20

Dead compensation
dither signal
Gain
Ramps

Question 21

What are the two types of pressure compensators?

Answer 21

bypass
Restrictor

Question 22

What are three types of valve elements to control flow in a directional control valve?

Answer 22

sliding spool
Rotary spool
Poppet

Question 23

what are the two types of pressure relief valves?

Answer 23

Maximum relief valve
Unloading valve

Question 24

what six input devices provide signals to the amplifier card?

Answer 24

joystick
PLC
potentiometers
Temperature sensor
Pressure transducers
Tach generators

Question 25

what is used to to control the electrical input of a proportional valve?

Answer 25

Amplifier card

Question 26

what is the ramp function?

Answer 26

It controls how fast the voltage to the solenoid is increased or decreased

• it controls acceleration and deceleration*

Question 27

what is special about a proportional solenoid?

Answer 27

It can move to an infinite number of positions

Question 28

what is metre in flow control?

Answer 28

Controls the flow going into the cylinder to control its speed

Controls extension and retraction

Question 29

Where would you place a metre in flow control valve if you want to control extension and retraction?

Answer 29

Before the directional control valve

Question 30

what happens if the spring on a sequence valve is set too low?

Answer 30

The second cylinder will move too soon

Question 31

what is venting a relief valve?

Answer 31

Unloading the entire system from our location, remote from the relief valve

Question 32

What are the three types of flow control valves?

Answer 32

metre in
Metre out
Bleed off

Question 33

what happens if the spring on a sequence valve is set too high?

Answer 33

The second cylinder will not move

Question 34

What are the three types of control valves?

Answer 34

pressure control
Flow control
directional control

Question 35

what are metering notches?

Answer 35

Notches in the school that control the flow rate from the valve

Question 36

where is the relief valve placed on the stack valve?

Answer 36

Closest to the sub plate

Question 37

where is the directional control valve placed on a stack valve?

Answer 37

At the top of the stack

Question 38

what is the difference between a stack valve and a cartridge valve?

Answer 38

Cartridge valves use a poppet stack valves use a spool

Question 39

what are the two types of cartridge valves?

Answer 39

Screw in
Slip in

Question 40

What is the main advantage of a proportional valve over a servo valve?

Answer 40

They are more rugged and dirt tolerant

Question 41

what is the purpose of an open school centre design?

Answer 41

It allows the pump to circulate freely, but does not lock the cylinder

Question 42

what is the purpose of a closed spool centre design?

Answer 42

It locks the cylinder and blocks the flow

Question 43

What is the purpose of a float spool centre design?

Answer 43

It shuts off the pump flow, but allows motor to coast freely

Question 44

what is the purpose of a tandem school centre design?

Answer 44

It locks the cylinder, but allows the pump to circulate back to the reservoir