Check, spool, orifice, and spring testing
Exercises and observations
Basic Hydraulic Symbol Experiment
1. Select Free>4 Motor Speed + Locking, from the drop-down list.
♦ Click on one of the blue circles to activate the spool valve.
♦ Click on both blue circles (the middle) and observe how the spool valve switches.
♦ Click on and drag the green pressure gauge and place it over the motor to display its operating values.
♦ Observe how the directional valve switches the direction of the flow and therefore rotation of the motor.
♦ Deactivate the directional spool valve (both circles blue) and observe how the check valves close, to lock the motor in position.
♦ Re-activate the spool valve and consider why both one-way check valves open, and how one allows backflow through it.
♦ Click on the variable orifice symbol. Adjust the size of the orifice and observe the effect this has on the moving cylinder.
♦ De-energise both solenoids and consider why the directional valve returns to its middle position.
Consideration 1: In this motor circuit the in-line poppet check valves open to allow flow in both directions.
Question 1: Why are the poppet valves NOT just allowing flow in one direction?
Consideration 2: Spool valves have no direct metal to metal contact so will always exhibit some fluid leakage.
Question 2: Which valve operates by moving a spool along a bore?
Consideration 3: A smaller orifice will generate a higher pressure drop with the same flow or reduce the flow with the same pressure drop.
Question 3: What happens to the cylinder speed when the orifice size is changed?
Consideration 4: Most spool valves have either two or three control positions and either one or two solenoids or actuators.
Question 4: What are the springs used directional control valves?