Applied hydraulic and pneumatic Assignment one Date given 12/06/26 Due date 19/06/26 Time 08:00

a) The system shown is a hydraulic system.

b) The operation of the system is as follows:

1. Power Unit (9): The pump (6) draws hydraulic fluid from the reservoir (8) through the filter (7) and delivers it under pressure to the system. The pressure relief valve (5) protects the pump and the entire system from excessive pressure by diverting any surplus fluid back to the reservoir.
2. Directional Control Valve (4): This is a 4/3-way directional control valve. It directs the flow of pressurized fluid to the double-acting cylinders (1 and 2).
   • In its center position, the valve typically blocks all ports, holding the cylinders in their current positions.
   • When shifted to one operating position, pressurized fluid is directed to one side of the cylinders (e.g., to extend them), while return fluid from the other side flows back to the tank.
   • When shifted to the other operating position, the flow is reversed, causing the cylinders to retract.
3. Cylinders (1 and 2): These are double-acting hydraulic cylinders that convert hydraulic pressure into linear mechanical motion, performing work.
4. Counterbalance Valves (10 and 11): These are pilot-operated counterbalance valves. When the directional control valve (4) directs fluid into a cylinder port, the check valve within the counterbalance valve allows free flow, enabling the cylinder to move. When fluid needs to flow out of a cylinder port (e.g., during retraction or lowering a load), the relief valve portion of the counterbalance valve prevents uncontrolled movement. It requires a pilot pressure (from the opposite cylinder line or system pressure) to open, allowing controlled fluid release and preventing the load from "running away." This ensures smooth and controlled operation and holds the load in position when the directional valve is centered.

c) Part 10 is a pilot-operated counterbalance valve. Its purpose is to:

• Prevent uncontrolled movement or "runaway" of the hydraulic cylinder, especially when supporting a heavy load or when gravity could cause rapid descent.
• Hold the load securely in position when the directional control valve (4) is in its neutral (centered) position, preventing cylinder drift.
• Ensure controlled and smooth lowering or retraction of the load by requiring a pilot pressure to open the relief valve, regulating the flow out of the cylinder.