Hydraulic Sequence Valve
A hydraulic sequence valve is a type of pressure control valve, used to ensure that multiple actuators in a hydraulic system (such as cylinders or hydraulic motors) operate in a preset sequence according to pressure settings.

Working principle: When the hydraulic pressure in the line reaches the set value, the sequence valve opens, allowing oil to flow to the next circuit and activating the subsequent actuator.

Main function: To achieve sequential operation of multiple actuators with a single hydraulic power source.

Features
• Enables one pump to drive multiple cylinders sequentially.
• No additional electrical control required; sequence is determined purely by pressure.
• Simplifies circuit design and control systems.

Applications
1. Machining Fixtures — Activate the positioning cylinder first, then the clamping cylinder, ensuring the workpiece is positioned correctly before clamping.
2. Molding / Die Casting Equipment — Mold closing → pre-pressing → high-pressure locking, ensuring proper processing quality by sequential action.
3. Presses / Punching Machines — Sequence valves control multi-stage pressing actions, e.g., fast advance followed by slow pressing.
4. Handling / Lifting Mechanisms — Ensures the platform is lifted before locking, or safety devices are released before cylinder activation.
5. Hydraulic System Safety Control — Prevents multiple actuators from moving simultaneously, avoiding interference or hazards.

Example
Suppose a hydraulic fixture requires the sequence “positioning → clamping”:
• The pump supplies oil simultaneously to both the positioning cylinder and the clamping cylinder.
• The positioning cylinder’s circuit has no sequence valve, allowing it to move first.
• The clamping cylinder’s circuit is equipped with a sequence valve set to a higher pressure than the positioning cylinder.
Once the positioning cylinder completes its stroke and back pressure builds up, the system pressure rises to the valve’s set value → the valve opens → oil flows into the clamping cylinder → completing the required sequence.