Pilot Operated Valve
A pilot operated valve is a two-stage architecture that drives the large main spool with a small pilot pressure rather than directly with lever force. Pilot pressure is typically in the 20–40 bar range and is carried by thin pilot hoses. Operator lever effort drops accordingly, and the control station can be moved away from the valve.
The force required to move the main spool increases as the valve grows, and past a point it can no longer be driven by hand. The pilot stage solves this problem: a small joystick valve produces a pilot pressure proportional to lever travel; this pressure acts on the end of the main spool and shifts it proportionally.
- Benefit: lever effort drops to the level of a few newtons and ergonomics improve noticeably.
- Requirement: a separate pilot supply line, a pilot filter, and usually a small accumulator.
- Fault symptom: if pilot pressure drops, motions slow down or cannot reach full opening.
This distinction simplifies retrofit kit selection: on a pilot operated machine the operator lever is already light, so the force that must be applied to the lever is low. On heavy, directly mechanically operated valves, the lever's actual force should be measured and the choice between HCT400 and HCT402 made accordingly.
Where this term is used: Connect Plus and Minus, Run: Installation That Does Not Depend on Technical Staff