1. Basic definition
The low-pressure gate valve is a fully open/closed valve specially used in the low-pressure pipeline system. The movement direction of its opening and closing parts (gate) is perpendicular to the flow direction of the fluid. It can only realize the full opening or closing function and does not have the ability to adjust the flow.
2. Structural characteristics and types
Main structure
Gate type: Parallel gate: The sealing surfaces on both sides are parallel. It is often used in low-pressure small and medium-sized pipelines (DN50-400mm). The spring or thrust wedge block assists the sealing;
Wedge gate: The sealing surface is wedge-shaped. The positive pressure is decomposed by the valve stem thrust to assist the low-pressure sealing, but the low-pressure application is less.
Valve stem form: Open stem structure: Suitable for small-diameter (DN≤80mm) scenes, intuitively displaying the valve opening;
Non-dark stem structure: The valve stem nut is in direct contact with the medium, suitable for large-diameter or space-constrained installation environments.
Sealing mechanism
Low-pressure working conditions rely on the rigid contact between the gate and the valve seat or the use of elastic elements (such as springs) to enhance the sealing performance and compensate for the impact of insufficient medium pressure.
3. Applicable scenarios and limitations
Typical applications :
Low-pressure (≤1.6MPa) liquid transportation scenarios such as fire protection pipe networks and municipal water supply systems;
Non-corrosive medium control such as sewage treatment and irrigation systems.
Limitations :
Not suitable for high-pressure or particle-containing, viscous medium environments, and is prone to leakage due to wear of the sealing surface;
High-temperature scenarios require limited use (the upper temperature limit of gray cast iron material is about 120℃).
4. Advantages and disadvantages analysis
Advantages :
Low fluid resistance, negligible pressure loss when fully opened;
Low operating torque, economical maintenance cost.
Disadvantages :
Large dimensions, large space required for installation;
Frequent opening and closing can easily cause scratches on the sealing surface, reducing service life.
Summary
Low-pressure gate valves are mainly parallel gates and concealed stem structures, which adapt to the needs of low-pressure pipeline systems through simple and reliable opening and closing mechanisms. However, their design and selection need to comprehensively consider the medium characteristics, space limitations and sealing durability.