301 F (A) - Hydraulic Control Valves

Question 1

What is Spring Constant?

Answer 1

The Pounds per inch of compression to express the stiffness of a spring

Question 2

What is cracking pressure?

Answer 2

Smallest amount of pressure to overcome spring pressure.

Question 3

What purpose does a Backpressure Valve serve?

Answer 3

This controls actuator movement by restricting the oil.

Question 4

What are the 4 functions provided by an Accumulator?

Answer 4

Energy Storage Shock Absorption Gradual Pressure buildup Constant Pressure Maintenance

Question 5

What is the reasons for using a Circuit relief valve?

Answer 5

Limit circuit pressure, handle shock loads.

Question 6

What are the three factors controlled by Pressure Control Valves?

Answer 6

Limit or Regulate Pressure Create a pressure condition for control Cause actuators to follow a certain order

Question 7

What is an Unloader Valve used for?

Answer 7

Used to relieve pump pressure once circuit pressure is reached and an accumulator has been charged, and a check valve to retain that pressure.

Question 8

What is valve modulation?

Answer 8

The constant opening and closing of a valve to balance flow.

Question 9

How is speed within a flow control valve determined?

Answer 9

By the internal capacity of the actuator and Input flow rate supplied

Question 10

What does a counterbalance valve do?

Answer 10

A Normally closed valve blocking return flow from a cylinder on either side to prevent drifting when holding a load.

Question 11

What function does a Sequence Valve offer?

Answer 11

Causes circuits to follow a certain order,

Question 12

Explain a Lock Valve

Answer 12

A set of pilot operated check valves that hold loads when lines fail. These also prevent drifting due to leakage and stops the load from over speeding the actuator.

Question 13

What is a Direct Acting Pressure Control Valve?

Answer 13

A Valve where the pressure is allowed to directly act upon the spring force.

Question 14

What is the purpose of a Hydraulic Accumulator?

Answer 14

To store hydraulic energy under pressure

Question 15

How is the amount of flow through an orifice determined?

Answer 15

Size and Shape of Orifice Pressure drop (Lower pressure = Higher Flow) Oil Viscosity

Question 16

What purpose does a Brake Valve have? How does it work?

Answer 16

To prevent overspeeding of a load. Unless the valve sees equal pressures it will not allow movement. Moving loads create a low pressure area.

Question 17

Explain a Priority Flow Divider

Answer 17

These are a normally closed valve with an orifice allowing one circuit to be supplied first. When the pressure within that circuit builds, pilot lines from it will open the flow divider to allow the second part of the circuit to operate.

Question 18

What are the three styles of Gas Charged Accumulator?

Answer 18

Piston Bladder Diaphragm

Question 19

What function does a pressure reducing valve serve?

Answer 19

Allows a circuit to operate on a lower max pressure than the rest of the system. Normally Open with pilot pressure sensed on valve outlet.

Question 20

What is a High-Low configuration?

Answer 20

This uses two pumps, where one is fitted with an unloader valve. When the system encounters higher pressures due to work, it unloads one pump allowing for higher torque lower flow. When loads are light both pumps output allowing for faster actuator speeds.

Question 21

What is the purpose of a relief valve?

Answer 21

To set a maximum pressure within a given system or circuit

Question 22

What causes Pressure Intensification?

Answer 22

Amount of return line restriction Ratio between base and rod end surface areas Force increase created by load

Question 23

What is pressure override?

Answer 23

The difference between cracking pressure and full flow.

Question 24

What is a pilot operated pressure control valve?

Answer 24

A valve that allows pilot pressure to set its cracking pressure and a main spring determining the pressure override between full flow and cracking pressure.

Question 25

What are the three types of direct acting pressure control valves?

Answer 25

Ball, Poppet and Guided Poppet

Question 26

What is another name for a Pilot Operated Pressure Control Valve?

Answer 26

A Compound pressure control.

Question 27

What are the three types of a Hydraulic Accumulator

Answer 27

Weighted Spring Gas Charged

Question 28

How does a pressure compensated flow control valve regulate flow?

Answer 28

The spring poppet gets acted on by outlet pressure, reducing inlet pressure being reduced by equal amount of difference. Inlet: 1000 PSI at 5 GPM Outlet side of Orifice: 500 PSI Compensator changes Now outlet gets 2.5 GPM instead of 5 GPM.

Question 29

What is the normal position of a valve?

Answer 29

When the valve has no hydraulic pressure acting upon it.