The excavator pipe-rupture valve is used wherever so required by the standards ISO 8643 and EN 474 for excavators with a lifting device (e.g. a load hook on the bucket). The actuators concemed are the lift cylinder, the stick cylinder and the adjusting cylinder.
It is also possible to envisage other machine applications in which a pipe rupture on the actuators could produce dangerous situations (e.g. machines for materials handling and demolition). The excavator pipe rupture valve, type ESV (Excavator Safety Valve), prevents uncontrolled lowering of the actuator in the event of a pipe or hose rupture. In addition, the ESV valve holds the actuator in its position when the main valve is centered. The valve includes a two-stage, secondary pressure-relief function, which protects the actuator against overload. The pressure relief is independent of any back pressure in port A. For main spools with closed center position and secondary valve connected in series, no pressure summing occurs. There is no need for a largebore, external tank return line.
Thanks to its load-independent, two-stage opening principle, variations in load pressure - even right up to the maximum - have no effect on the fine control characteristics and the hydraulic performance of the equipment. The design of the valve means that it can be operated by very small lowering pressures. This means that excavators with and without a materials handling function can be equipped with the same basic hydraulic system (the machine's work cycles remain the same).
