The lever safety valve, also commonly known as the weight-loaded or dead-weight safety valve, is one of the earliest types of pressure relief devices. It operates on a simple mechanical principle using a lever and weight system to control valve opening.

Basic Components

A typical lever safety valve consists of several key components: the valve body, valve seat, valve disc (or valve core), a pivoted lever, and a movable weight. The valve body houses the seat and disc assembly, while the lever transmits force from the weight to the valve stem.The main safety valve product names of China Safety Valve Network include:Explosion Wave Proof Safety Valve,F2-250/400 Main Safety Valve,Fan Engine Safety Valve,Freezer-used Safety Valve,Gas Specific Fall Lift Safety Valve,GA49H-DN20 Pulse Safety Valve,High Temperature and Pressure Fall Lift Safety Valve,Hydraulic Safety Valve,Impulse Safety Valve

Operating Principle

The working principle of a lever safety valve is based on the balance of moments around a pivot point. The weight is positioned on the lever, and its gravitational force creates a moment that acts through the lever and pivot to press the valve disc firmly against the seat via the valve stem. This keeps the valve closed under normal operating conditions.

The system pressure acts on the underside of the valve disc, creating an upward force. When this upward force multiplied by its lever arm produces a moment that exceeds the moment created by the weight, the valve disc lifts off the seat, allowing the medium (such as steam) to discharge. This is the valve opening or "popping" action.

Once sufficient pressure is relieved and the system pressure drops, the moment from the weight again becomes dominant, and the valve closes automatically.

Pressure Adjustment

One significant advantage of the lever safety valve is the ease of set pressure adjustment. By simply moving the weight along the lever, the effective moment arm changes. Moving the weight inward toward the pivot increases the set pressure, while moving it outward decreases the set pressure. This allows for convenient field adjustment without special tools.

Advantages and Limitations

Lever safety valves offer several benefits: simple construction, straightforward adjustment, and reliable operation. However, they also have notable drawbacks. They are relatively large and heavy compared to spring-loaded alternatives. Additionally, they are sensitive to vibration, which can cause premature opening or leakage.

Typical Applications

Due to their size and weight characteristics, lever safety valves are primarily used in medium and low-pressure small boilers. In modern high-parameter, large-capacity boilers, they find application as pilot valves for controlling main safety valves rather than as primary relief devices.

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