Hydraulic Lock Valves: A Guarantee of Load Security
Hydraulic Lock Valves: A Guarantee of Load Security
Hydraulic Lock Valves: A Guarantee of Load Security
Hydraulic systems offer incredible power to lift, move, and precisely position heavy loads. However, keeping this force in check is vital, especially when it is necessary to securely hold a load in a specific position. This is where Hydraulic Lock Valves (Pilot Operated Check Valves) come into play.
What is a Lock Valve and How Does It Work?
A hydraulic lock valve is basically a check valve that can be opened by pilot pressure. Its main job is to keep the load in the desired position by completely blocking the flow of the hydraulic cylinder or motor in a line, even if there is a pressure drop or line break in the rest of the system.
Working Principle
Locked Status (Off):
The valve is normally in a closed position.
When mounted on the line on one side of a hydraulic cylinder, it blocks the flow either to or from the load-holding side of the cylinder.
The spring on the valve pushes the check valve element into its seat without a leak. In this case, the pressure caused by the load compresses the valve even more, preventing it from moving.
Open Status (Release):
When the load needs to move (e.g. lowering a crane), a pressure is applied to the pilot port of the valve.
This pilot pressure moves a small piston within the valve.
The piston separates the check valve element from its seat and thus allows oil to flow freely.
When the pilot pressure is removed, the spring returns the valve back to the closed, locked position.
Uses and Importance
Hydraulic lock valves are indispensable, especially in mobile and industrial hydraulic applications where life safety and equipment security are paramount.
Mobile Cranes and Lifting Platforms: Prevents the load or platform from descending unintentionally.
Forklifts and Construction Machinery: Ensures that the fork or attachment remains in its designated position.
Excavator Booms and Buckets: Helps maintain position.
Hydraulic Presses: Maintains the position of the press during operation.
Why Are They Critical?
A simple hose burst or a leak in the main control valve would have caused uncontrolled load movement (load drop) if it weren't for the lock valve. Lock valves serve as backup security against such failures.
Technical Parameters and Considerations
Here are some technical parameters to consider when selecting or designing a lock valve:
- Pilot Rate ()
The pilot ratio is a critical factor that determines the pilot pressure required to open the valve.
Here, the surface area of the pilot piston is the surface area of the valve element.
High Ratios (4:1 or 6:1): Opens the valve with less pilot pressure. It makes control easier.
Low Ratios (2.5:1 or 3:1): Requires higher pilot pressure to open the valve but reduces the risk of unintentional valve opening under high vibration or load shocks.
- Leakage
High-quality lock valves have near-zero leakage properties. This is imperative so that the load does not lose position, even over time. To achieve this, poppet type valves are generally used.
- Single and Double Acting
Single Lock Valve: Locks the flow to only one side of the cylinder (usually the side where the load is held).
Double Lock Valve (Double Pilot Operated Check Valve): Locks the flow on both sides of the cylinder. When pilot pressure is applied to one side, the valve on the other side opens. This is standard for double-acting cylinders.
Installation and Maintenance Tips
Proper Mounting Orientation: The lock valve should be installed as close as possible to the cylinder or motor line where it needs to hold the load. This minimizes the impact of any malfunctions that may occur in the pipe or hose between the valve and the cylinder.
Pressure Adjustment: Ensure that the pilot pressure is sufficient for the system to dependably open the valve under maximum operating pressure. Include the pilot rate in this calculation.
Cleaning: Cleaning the hydraulic system is critical for the proper functioning of the precise seat surfaces and pistons inside the lock valve. Contamination can lead to leakage or stuck valve.
Despite their simple design, hydraulic lock valves are one of the most important links in the hydraulic safety and efficiency chain. Choosing a suitable lock valve for your system and its correct integration will directly enhance the safety of your operations.