Basic Principles Test

1. Select step 1 (dropdown menu 1) Pilot pressure against a spool

• Adjust the pilot pressure on the spool by dragging the slide bar.

• Observe how the spool moves against the spring force.

2. Select step 2 (dropdown menu 2) Proportional valve spool position changes orifice size.

• Observe how the changing orifice size, changes the flow through the valve.

3. Select step 3 (dropdown menu 3) Load pressure on the gear motor.

• Change the load pressure and note how the pressure drop across the spool changes.

• Observe how the flow changes as the load pressure changes.

4. Select step 4 (dropdown menu 4) Spool clearance

• Consider what pressures will exist on either side of each spool lands.

• Use the pressure drop information to predict leakage flow rates and paths.

5. Select step 5 (dropdown menu 5) O-ring seals

• Consider how the friction from an O-ring will affect seal movement.

• Operate the spool to see the effects on hysteresis from the seal.

6. Select step 6 (dropdown menu 6) Restricted volumes

• Consider how an orifice that restricts flow from a chamber will affect seal movement.

• Operate the spool to see how the trapped volume affects its speed of movement.

Experiment 1: Directional valves are simply open or closed. Proportional valves have notches that control the orifice size.

Question 1: How is flow controlled in a directional valve circuit?

Answer

Experiment 2: Flow is controlled by the size of a restriction and the pressure drop across it.

Question 2: Why does the flow change when the load pressure is changed?

Answer

Experiment 3: Every spool valve has a small leakage due to the clearances between the bore and spool.

Question 3: What factors will affect the leakage flow rate in each spool valve?

Answer