Hydraulic valves part 2 - part A

Question 1

How do flow control valves control the speed of an actuator?

Answer 1

-internal capacity of the actuator (larger is slower at a given flow rate) -input flow supplied to the actuator

Question 2

Where is a pressure drop created?

Answer 2

Pressure drop is created as flow through an oriface is restricted.

Question 3

Where is pressure the lowest in a flow control valve?

Answer 3

Always lowest inside the oriface (the smallest part) where fluid velocity is greatest.

Question 4

A non fixed oriface with a check valve allowing free flow in the reverse direction is also known as a?

Answer 4

Throttle valve

Question 5

The amount of flow that passes through an oriface is determined by?

Answer 5

-Oriface size and shape -the pressure drop across the oriface (the greater the drop the greater the flow) - the viscosity of the oil

Question 6

How does an adjustable (variable) oriface regulate flow?

Answer 6

The valve can be adjusted to change the oriface size.

Question 7

What is the difference between a non-pressure compensated and a pressure compensated valve?

Answer 7

Pressure compensated valves can maintain flow at the outlet of the valve regardless of changes in circuit pressure. Non-compensated valves can not maintain flow.

Question 8

How does a pressure compensating valve maintain flow rates?

Answer 8

By maintaining the pressure drop through the oriface.

Question 9

What are the three ports on a bypass type pressure compensated flow control valve called?

Answer 9

-inlet -regulated flow -excess flow

Question 10

Why are bypass type pressure compensated flow control valves inefficient?

Answer 10

Wasted energy is lost in the flow of excess oil

Question 11

What are the ports on a restrictor type pressure compensated flow control valve?

Answer 11

Inlet and outlet

Question 12

What type of pump is best used with a restrictor type pressure compensated flow control valve?

Answer 12

A pressure compensated variable displacement pump.

Question 13

How can a restrictor type pressure compensated flow valve allow full flow in the reversed direction?

Answer 13

A restrictor type flow control with a reverse flow check valve will allow full flow in reversed direction.

Question 14

How do you determine which direction a restrictor type pressure compensated flow control valve with a flow check valve is allowing full flow on a schematic?

Answer 14

The direction of the check valve determines full flow conditions.

Question 15

What are some considerations that need to be made when designing a circuit where a linear actuator is metered by a restrictor type flow valve?

Answer 15

Restrictor type flow valves can create conditions where cavitation and pressure intensification are caused inside the cylinder depending on application

Question 16

How do priority flow control valves differ from bypass type flow control valves?

Answer 16

The bypass line oil in a priority flow control valve is used to run a secondary implement instead of excess oil sent to tank

Question 17

How do priority flow control valves ensure that the priority circuit always gets flow first?

Answer 17

Flow has to be satisfied in the priority circuit before pressure can be built in the valve and open the port and direct flow to the secondary implement

Question 18

In a priority flow control valve what happens if to the secondary implement if the primary circuit is dead headed and system pressure goes over relief?

Answer 18

The valve will stay shut and will not allow flow to run the second implement.

Question 19

How are priority flow control valves designed to ensure flow to the secondary circuit regardless of pressure being deadheaded in the primary circuit?

Answer 19

A circuit relief can be added to the primary circuit to relieve pressure and allow flow through the valve to open the port for the flow of oil to the secondary implement. Pressure still has to build in the primary circuit first but the relief pressure (set lower than main relief) will open if overcome and flow will continue in the valve.

Question 20

How does a proportional flow divider work?

Answer 20

The valve is pressure compensated and flow is divided to each outlet, as pressure is built at one circuit the compensator spool moves to limit the pressure drop and maintain flow to that circuit. Flow is maintained at both outlets regardless of pressures seen.

Question 21

What type of flow control valve is used in this circuit?

Answer 21

Pressure compensated flow control

Question 22

What type of flow control is used in this circuit?

Answer 22

Restrictor type pressure compensated flow control valve

Question 23

What type of flow control is used in this circuit

Answer 23

Restrictor type flow control with reverse flow check valve

Question 24

What type of flow control is used in this circuit?

Answer 24

Priority flow control valve

Question 25

What type of flow control is used in this circuit

Answer 25

Proportional flow divider

Question 26

State the type of flow control for an application where the actuator load changes direction and strength

Answer 26

Metered out flow control valve

Question 27

A bypass type flow control valve works best with what pump?

Answer 27

A fixed displacement type pump.

Question 28

How is a flow valve shown that it is pressure compensated on a schematic?

Answer 28

the arrow drawn through the path of oil shows that it is a pressure compensated device.

Question 29

How is an oriface shown that it is adjustable on a schematic?

Answer 29

a single arrow through the oriface symbol.

Question 30

Can a proportional flow divider have a priority circuit in terms of flow?

Answer 30

Yes, the spool can have a larger drilling on one side than the other to prioritize the flow characteristics. For example: flow control can be 70/30 to the two ports to run an implement with larger flow requirements along with and implement with smaller flow requirements.