301 F (B) - Hydraulic Valves II Flashcards
How are Directional Control Valves Classified?
Type (Rotary, Poppet, Sliding Spool) Condition and Number of Paths Number of Positions Actuation Methods Detents
What is the common material used for construction of Directional Control Valve housings?
Fine Grain Cast Iron or Aluminum
What is the simplest of all Flow/Directional Control Valves?
Poppet Valve
Explain some features of a Sliding Spool Valve
Minimum Leakage
Metering Notches for Feathering
Explain some advantages/disadvantages of Rotary spool valves.
Higher amount of leakage
Used for lower pressures and flow rates
What is a Diverter Valve?
A Two Position, Three Way Directional Control Valve
What is a Directional Control Valve Float position?
Where a Double Acting Cylinder has its base and rod ends both supplied to tank. Allowing the cylinder to float and be used in a variety of uses.
When an open centre directional control valve is being used, what type of pump is being used within this system?
Fixed Displacement Pumps
What is a series passageway?
The passageway through Open Centre Open Port directional control valves
What are 3 ways that directional control valves are actuated?
Mechanical through Levers
Pilot Operated by Hydraulic or Air
Electronically through Solenoids
What does a pilot operated directional control valve require to be effective?
A Tandem pilot pressure pump will be used.
What is one disadvantage of using electrical actuators for directional control valves?
There is no feathering possible.
How is a detent on a directional control valve achieved?
Through the use of spring loaded balls to latch position of the spool.
What types of pressure control valves can be mounted inside a directional control valve?
Relief
Load Check
Anti Cavitation
Flow Compensator
What is a load check valve?
Check ball mounted in the pump supply port of a directional control valve, preventing loads from causing a higher pressure overrunning pump.
What is an Anti Cavitation Valve?
Check ball on return line of actuators, used to prevent air from being sucked in when a heavy load pulls the piston down faster than the pump can fill the rod end.
This acts like a regeneration valve.
What is a Flow Compensator Valve?
A Pressure Compensator valve installed in the directional control valve with a checkball installed on the outlet of the work ports. This ensures constant pressure drop in and out of the Controls.
What are two styles of Control Valve assemblies with multiple controls?
Unibody style, cast as one housing.
Valve Stacks, stacked individual valve assemblies.