In hydraulic-system mechanics, overall stability and component life depend not only on the main power elements but also on the control components that define the safety limits. Foremost among these protective components is the end-of-stroke valve. Although compact in construction and simple to integrate, it protects some of the most critical parts of the hydraulic circuit. Analysis of cylinder, pump and hydraulic-line failures encountered in the field shows that systems can be exposed to serious risks when an end-of-stroke safety mechanism is absent or incorrectly calibrated.

Operating Logic and Function of the End-of-Stroke Valve

As a telescopic cylinder extends, it cannot move any farther once its final stage reaches the mechanical limit and the cylinder is fully open. The pump, however, continues to rotate and continues supplying oil to the system.

Because the fluid is incompressible and has no available flow path, system pressure tends to rise suddenly. This uncontrolled pressure increase, or pressure shock, can deform cylinder seals, overload the mechanical limits of the stages, cause leakage at hydraulic hoses and fittings, and place excessive load on the pump’s internal structure.

The end-of-stroke valve acts precisely at this point. The moment the cylinder reaches its mechanical limit, a physical trigger shifts the valve; it prevents pressurised oil from continuing to force the cylinder and diverts the flow safely to the tank. System pressure is thereby reduced to a safe range.

HMLIFT End-of-Stroke Valve Configurations

HMLIFT VS3600-series end-of-stroke valves are designed with different operating principles to meet the requirements of the hydraulic-circuit architecture:

• 1. Normally Closed Models: The valve remains closed and allows oil to flow to the cylinder until an external physical force acts on the trigger mechanism. When the cylinder reaches full stroke, mechanical contact opens the valve and activates the protection line. This group includes models VS36001510-1511 and pull-rod models VS36001516-1515.
• 2. Normally Open Models: These provide an alternative circuit design based on inverse system logic, activating the protection line by closing the flow path at the moment of triggering. This group includes models VS36001520-1521 and pull-rod models VS36001523-1522.
• 3. Trigger Geometries (Direct and Pull-Rod): The physical triggering method depends on the body and chassis connection geometry.
  • Direct-Acting Types: Operate when a moving part of the cylinder or body presses directly on the valve pin.
  • Pull-Rod Types: Provide alternative mounting solutions triggered by a pulling action through a mechanical rod mechanism.

Effects of Incorrect Configuration and Calibration

Maximum effectiveness of the end-of-stroke safety system depends on correct installation and precise positioning:

• Early Triggering: If the valve acts well before the cylinder reaches its actual stroke limit, the body cannot reach the target tipping angle and material discharge remains incomplete.
• Late Triggering: If the valve still does not actuate after the cylinder has reached its mechanical stop, protection is not provided in time and the system is exposed to pressure shock.

Conclusion

End-of-stroke valves with standard connection sizes such as G 3/4″ or G 1″ and flow capacities of 110-140 L/min are fundamental safety elements for hydraulic integrity. Including this component in the system design and checking pin mobility and sealing during periodic maintenance are essential engineering requirements for minimising downtime in vehicle-mounted equipment.