Question

1. As a mechanical engineer, design a hydraulic circuit with pushing and pulling force using a lever. Please consider a minimal usage of components in your design. Explain the operation based on directional control valve position. Use symbols in accordance to ISO 1219.

2. A manufacturing machine supplier needs your help to design a hydraulic circuit for 2 cylinder output that operate in sequence, one after another. Please consider a minimal usage of components in your design. Explain the operation based on directional control valve position. Use symbols in accordance to ISO 1219.

3. In your opinion, discuss 3 most effective safety strategy to ensure safety operation of hydraulic fluid.

*Project Task (Circuit design and analysis)

Answer 1

Task 1: To design a hydraulic circuit with pushing and pulling force operated using a lever.

Please refer to attached for task 1. This system contains the following components:

1. Lever operated 4/2 DCV
2. Hydraulic pump
3. pressure relief valve
4. tank/reservoir
5. 4/2 DCV

In the first position of the 4/2 DCV the pressurized oil moves from Pump to cap end of cylinder and thus actuated the cylinder in forward direction (Push force).

In the second position of the 4/2 DCV the pressurized oil moves from Pump to rod end of cylinder, thus makes the cylinder to retract in opposite direction. (Pull force)

When the cylinder gets completely extended or retracted, the pressure inside the cylinder rises which makes the excess oil leave the system using pressure relief valve.

Task 2: To design a circuit in which two cylinders work one after the another in a sequence:

The components used in this system are:

1. Hydraulic pump
2. Pressure relief valve
3. Solenoid operated 4/3 DCV
4. 2* sequencing valves
5. 2* double acting cylinders (Named as cylinder 1 and 2)

When pressurized oil flows from pump to 4/3 DCV,

In position 1,oil flows to cylinder 1 and sequencing valve 1. The pressure to open the sequencing valve is always higher than pressure require to operate cylinder 1. Thus when cylinder 1 gets fully actuated, pressure inside the system rises and thus sequencing valve 1 opens causing the oil to flow into cylinder 2 and make it actuate.

In position 3,oil flows to cylinder 2 and sequencing valve 2. The pressure to open the sequencing valve 2 is always higher than pressure require to operate cylinder 2. Thus when cylinder 2 gets fully retracted, pressure inside the system rises and thus sequencing valve 2 opens causing the oil to flow into cylinder 1 and make it retract.

Since all the ports remain closed in position 2, hydraulic oil flows into the reservoir via pressure relief valve.

In my opinion, 3 most effective strategies to maintain safety operation of hydraulic fluid.

1. Hydraulic fluid can be extremely fatal when pressurized. A thin pressurized spray can cause enormous damage to machinery and human tissues. Thus to avoid such accidents, all the hose pipes and valve connections should be checked regularly and made leak proof.
2. Hydraulic fluid is inflammable in nature and even a small quantity of fluid when catches fire can damage the entire system. Thus a fire detection system and safety equipment like fire extinguishers must be always present.
3. Hydraulic fluid has excellent properties to reduce friction. It has very high viscosity which makes it slippery in nature. Hydraulic operations should always be performed on a rough ground where chances of slipping due to oil spills is less in compared to smooth surfaces.

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