Hydraulic valves part 2 - part A Flashcards
How do flow control valves control the speed of an actuator?
-internal capacity of the actuator (larger is slower at a given flow rate) -input flow supplied to the actuator
Where is a pressure drop created?
Pressure drop is created as flow through an oriface is restricted.
Where is pressure the lowest in a flow control valve?
Always lowest inside the oriface (the smallest part) where fluid velocity is greatest.
A non fixed oriface with a check valve allowing free flow in the reverse direction is also known as a?
Throttle valve
The amount of flow that passes through an oriface is determined by?
-Oriface size and shape -the pressure drop across the oriface (the greater the drop the greater the flow) - the viscosity of the oil
How does an adjustable (variable) oriface regulate flow?
The valve can be adjusted to change the oriface size.
What is the difference between a non-pressure compensated and a pressure compensated valve?
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.
How does a pressure compensating valve maintain flow rates?
By maintaining the pressure drop through the oriface.
What are the three ports on a bypass type pressure compensated flow control valve called?
-inlet -regulated flow -excess flow
Why are bypass type pressure compensated flow control valves inefficient?
Wasted energy is lost in the flow of excess oil
What are the ports on a restrictor type pressure compensated flow control valve?
Inlet and outlet
What type of pump is best used with a restrictor type pressure compensated flow control valve?
A pressure compensated variable displacement pump.
How can a restrictor type pressure compensated flow valve allow full flow in the reversed direction?
A restrictor type flow control with a reverse flow check valve will allow full flow in reversed direction.
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?
The direction of the check valve determines full flow conditions.
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?
Restrictor type flow valves can create conditions where cavitation and pressure intensification are caused inside the cylinder depending on application
How do priority flow control valves differ from bypass type flow control valves?
The bypass line oil in a priority flow control valve is used to run a secondary implement instead of excess oil sent to tank
How do priority flow control valves ensure that the priority circuit always gets flow first?
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
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?
The valve will stay shut and will not allow flow to run the second implement.
How are priority flow control valves designed to ensure flow to the secondary circuit regardless of pressure being deadheaded in the primary circuit?
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.
How does a proportional flow divider work?
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.
What type of flow control valve is used in this circuit?
Pressure compensated flow control
What type of flow control is used in this circuit?
Restrictor type pressure compensated flow control valve
What type of flow control is used in this circuit
Restrictor type flow control with reverse flow check valve
What type of flow control is used in this circuit?
Priority flow control valve
What type of flow control is used in this circuit
Proportional flow divider
State the type of flow control for an application where the actuator load changes direction and strength
Metered out flow control valve
A bypass type flow control valve works best with what pump?
A fixed displacement type pump.
How is a flow valve shown that it is pressure compensated on a schematic?
the arrow drawn through the path of oil shows that it is a pressure compensated device.
How is an oriface shown that it is adjustable on a schematic?
a single arrow through the oriface symbol.
Can a proportional flow divider have a priority circuit in terms of flow?
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.
