Application
Overcentre valves give static and dynamic control of loads by regulating flow into and out of hydraulic actuators. The Overcentre valve will stop the load from running away in the event of a hose burst. If open centre directional control valves are used, they will allow the thermal expansion relief of the hydraulic fluid. These valves provide excellent hose burst protection.
Operation
The check section allows free flow into the actuator (from 2 to 1) then holds and locks the load against movement (from 1 to 2). The pilot pressure in the pilot port (3) will give a controlled movement to piston when the pressure is applied.
The pressure required to open the valve and allow movement depends on the pilot ratio of the valve. For optimization of load control and energy usage, a choice of pilot ratios can be made available.
The pressure required to open the valve and start actuator movement can be calculated as follows:
Pilot Ratios
3:1
Best suited for extremely unstable applications such as long booms
4:1 Best suited for applications with variable load and unstable
machine structure
5:1 Best suited for applications with variable load and unstable
machine structure
7:1 Best suited for applications where the load remains relatively constant
Specifications
Max Flow
|
Up
to 400 litres/min
|
Max. Load Induced Pressure
|
270
bar
|
Relief Setting
|
350
bar
|
Cartridge Material
|
Working
Parts: Hardened and Ground External Surfaces: Zinc Plated
|
Operating Temperature
|
-20’C
to +90’C
|
Port Sizes
|
3/8”
BSP to 1.1/4” BSP
|
Leakage
|
Less
than 35 millilitres/min
|
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