How to Configure Hydraulic Cylinders in Series

Configuring hydraulic cylinders in series allows for synchronized movement or compound motion between multiple cylinders in a hydraulic circuit. Here’s a step-by-step guide to configuring hydraulic cylinders in series:

1. Understand the Series Configuration Basics

• In a series configuration, the rod end of one cylinder connects to the cap end of the next cylinder.
• This setup forces the oil to flow through each cylinder in sequence, resulting in simultaneous movement.
• Note that when configured in series, the stroke and speed of each cylinder may differ based on cylinder sizes.

2. Choose Compatible Cylinders

• The cylinders should ideally have the same bore and rod diameter to achieve synchronized movement.
• Differences in bore sizes can lead to variations in force and speed, potentially affecting performance.
• If different sizes are used, keep in mind that the smaller bore cylinder will have less force due to reduced hydraulic area.

3. Calculate the Required Flow Rate

• Flow rates will need to be managed carefully to ensure each cylinder moves at the desired speed.
• The flow rate into the first cylinder must account for the volume requirements of all cylinders downstream in the sequence.

4. Determine Pressure Requirements

• The pressure needed in a series configuration is cumulative; therefore, the pump must provide enough pressure to move each cylinder, considering any load on each cylinder.
• For example, if the system operates two cylinders, each requiring 1000 PSI, the pump needs to supply at least 2000 PSI to ensure both move correctly.

5. Connect the Hydraulic Lines in Series

• Connect the pressure line from the hydraulic pump to the cap end of the first cylinder.
• Connect the rod end of the first cylinder to the cap end of the second cylinder.
• Continue this process if you have more than two cylinders in the sequence.
• The return line from the last cylinder connects back to the tank or hydraulic reservoir.

6. Use Check Valves or Flow Controls as Needed

• Consider using flow control or check valves to prevent unintended movement and ensure steady motion between cylinders.
• Flow controls are especially useful if you need to adjust speed differences between cylinders.

7. Bleed Air from the System

• Air in the system can cause erratic movement and reduce the efficiency of the cylinders.
• Properly bleed each cylinder to remove any trapped air, ensuring smooth operation.

8. Test the System

• Once everything is connected, test the system at low pressure to verify correct movement and synchronization.
• Gradually increase to operating pressure and observe the movement of each cylinder, adjusting flow rates or pressure as needed.

Important Considerations

• Load Balancing: If each cylinder has a different load, movement may not be synchronized due to the varying resistance. Using load-holding valves can help manage this.
• Speed Matching: In a series circuit, the leading cylinder typically moves slower than the following cylinders. Adjust flow controls if specific speed adjustments are needed.
• Cylinder Selection: Using double-acting cylinders is generally preferable in series configurations for controlled retraction and extension.

By carefully configuring hydraulic cylinders in series, you can achieve compound movements while maintaining control over force and synchronization.

Calculation for Configure Hydraulic Cylinders in Series 

When configuring hydraulic cylinders in series, the key is understanding how the pressure and flow are distributed across the cylinders. In a series configuration, the hydraulic fluid flows from one cylinder to the next, so the force and motion output of each cylinder is directly affected by the one preceding it. Here's a step-by-step guide to calculate the main parameters.

1. Determine Cylinder Properties:

For each cylinder, identify:

• Bore diameter ($D$): diameter of the cylinder’s piston.

• Rod diameter ($d$): diameter of the piston rod.

• Stroke length ($L$): total distance the cylinder's piston can travel.

• Effective area of the piston side ($A_p$) and rod side ($A_r$).

• Piston Side Area:

  $$A_p = \frac{\pi D^2}{4}$$

• Rod Side Area:

  $$A_r = \frac{\pi (D^2 - d^2)}{4}$$

2. Flow Rate (Q):

• The flow rate into the first cylinder ($Q_{in}$) is provided by the pump.
• In a series setup, the flow rate leaving the first cylinder becomes the input to the next cylinder, and so on.

3. Force Calculation:

• Force on the Piston Side of Cylinder 1:

  $$F_1 = P_{in} \cdot A_p$$

• The output pressure after Cylinder 1 ($P_{out1}$) is calculated by:

  $$P_{out1} = \frac{F_1}{A_r}$$

• This $P_{out1}$ becomes the input pressure ($P_{in2}$) for Cylinder 2.

• Force on Cylinder 2: Using $P_{in2}$ calculated from Cylinder 1, the force on Cylinder 2’s piston side:

  $$F_2 = P_{in2} \cdot A_p$$

4. Velocity of Cylinders:

The velocity of each cylinder depends on the flow rate and effective area:

• Velocity of Cylinder 1 (V1): $$V_1 = \frac{Q_{in}}{A_p}$$
• Velocity of Cylinder 2 (V2) (if flow rate through the system remains constant): $$V_2 = \frac{Q_{out1}}{A_p}$$

where $Q_{out1}$ is the outflow from Cylinder 1.

Example

Given values:

• Cylinder 1:
  • $D = 50 \, \text{mm}$, $d = 25 \, \text{mm}$
  • $P_{in} = 100 \, \text{bar}$, $Q_{in} = 20 \, \text{L/min}$

1. Calculate $A_p$ and $A_r$.
2. Determine the force $F_1$.
3. Calculate $P_{out1}$ and proceed similarly for Cylinder 2.

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This framework provides a basis for calculating forces, velocities, and pressures in a series configuration for hydraulic cylinders.