Pressure Control Valves Flashcards
What do pressure control valves do?
Keep system pressures safety below a desired upper limit to maintain a set pressure in part of a circuit
What types of pressure control valves are there?
Relief, regulating/reducing, counterbalance and sequence
What are pressure relief valves used to do?
Control or limit,
Set to open at a predetermined set pressure allowing the component to protect the system
How does the relief valve operate?
Hydraulic pressure overcomes spring pressure, the valve opens and allows fluid back back to the reservoir.
As the pressure then drops it reseats the valve, closing it
What does the sequential valve do?
Allows flow to an actuator at a set pressure via the relief
The NRV allows flow to return from the actuator to the the reservoir
What does the relief valve do for the system?
To protect the pump from excessive pressure
What does the counterbalance valve do?
To prevent it from retracting due to the weight of its external load
Keep it from free falling by setting the pressure slightly higher
When the DCV is put in the middle position while lowering the load the counterbalance valve will do what?
Close immediately, causing an increase in pressure , however the counterbalance will open at the adjusted pressure therefore protecting over pressure
What is the purpose of a pressure regulating
Maintain reduced pressures in a specified location
Activated by downstream pressure, as this pressure reaches the setting the valve closes not allowing fluid to pass through and stoping a reduction in pressure
When the outlet pressure increases beyond the valve setting, the spool moves to partially block the outlet so….
Allowing enough fluid to pass to the outlet to ensure it maintains a preset pressure
What is the operation of a pressure reducing valve?
Flow is diverted to reservoir as pilot pressure overcomes spring pressure
As a flow is returned to reservoir downstream pressure reduces
Valve opens as spring pressure overcomes pilot pressure
