Heavy Duty Equipment Technician exam: Hydraulic systems

Key points

• Force = pressure x area. A bigger cylinder gives more force at the same pressure.
• Pumps make flow, not pressure. Pressure comes from resistance to flow.
• Flow controls cylinder speed. Pressure controls force.
• A relief valve sets the maximum system pressure.
• Contamination causes most hydraulic failures, so filters and clean practice matter.

Study tip

If an actuator is slow but strong, think flow. If it is fast but weak, think pressure or leakage.

Try these

1. A cylinder moves slowly but with full force. The likely cause is:

   1. Low relief setting
   2. Low flow
   3. Wrong fluid colour
   4. High pressure
   Show answer

   B. Low flow Speed comes from flow.

2. Pressure in a hydraulic system is created by:

   1. The pump alone
   2. Resistance to flow
   3. The reservoir
   4. The filter
   Show answer

   B. Resistance to flow Pumps make flow; resistance makes pressure.

3. A 10 sq in piston at 2000 psi produces:

   1. 200 lb
   2. 2000 lb
   3. 20 000 lb
   4. 200 000 lb
   Show answer

   C. 20 000 lb F = P x A.

Keep going

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