Sequence Valve
A sequence valve is the sequencing element that prevents a second motion from starting until the first motion reaches a certain pressure. The setting pressure is chosen according to the pressure level that indicates the first motion is complete; typically it is around 60-80% of system pressure. It provides sequential operation without electronic control.
The logic is simple: while the valve is closed, all flow goes to the first actuator. When that actuator bottoms out at end of stroke, line pressure rises, and once the set value is reached the sequence valve opens and flow is directed to the second actuator. The classic example is a die being clamped first and then pressed.
- Return flow: the valve body usually contains a check valve that allows free reverse flow.
- Setting pitfall: if the setting is too low, the second motion starts early and the first job is left unfinished.
- Drain: on externally drained types this line must return to tank unpressurized.
A sequence valve is a mechanical logic gate. The same sequencing can be built today with an electronic controller; but a sequence built on the hydraulic side keeps its behavior even if control power is lost. When adding electronic lever control, being aware of such built-in hydraulic logic makes it easier to understand why unexpected motion sequences occur.
Where this term is used: How Are Manual Hydraulic Levers Controlled Remotely? A Comparison of 6 Methods