1. Basic Definition
The fire hydrant gate valve is a key control component installed in the fire hydrant system. It realizes the full opening or closing control of the pipeline medium through the vertical lifting movement of the gate. It is specially used to cut off the water flow and ensure that the fire protection system can be quickly activated or closed in an emergency. Its core functions include controlling combustibles, isolating combustion-supporting materials, and regulating the fluid on and off of the fire water supply network.
2. Core structure
Gate and sealing surface
The gate is a flat plate structure that moves vertically. When closed, it forms a sealing surface with the valve seat to prevent the flow of the medium.
The sealing surface material is usually corrosion-resistant alloy or elastic material, which is suitable for impurities and impact pressure in fire water.
Valve stem drive mode
Rising stem gate valve: The valve stem is exposed, and the gate is driven to rise and fall by rotation. The opening and closing status is intuitively visible, which is easy to maintain but requires anti-corrosion treatment.
Non-seeking stem gate valve: The valve stem is built-in, only rotates but does not rise and fall, suitable for buried pipelines or concealed projects, but it is necessary to rely on the scale to judge the opening.
Additional design
Some models are equipped with self-locking devices or electric drive mechanisms to prevent misoperation and adapt to large-diameter pipes (such as DN300 and above).
3. Working principle
Opening and closing mechanism
Manually rotate the handwheel or electrically drive the valve stem to drive the gate to move up and down perpendicular to the water flow direction:
When open: The gate is lifted to the top of the valve cavity to form a full-diameter flow channel with minimal fluid resistance.
When closed: The gate completely presses the valve seat to block the flow of the medium, relying on the dual effects of mechanical thrust and medium pressure to achieve sealing.
Sealing characteristics
At low pressure, the valve stem thrust is used to force the seal, and at high pressure, the medium pressure assists in enhancing the sealing pressure ratio.
4. Application scenarios
Key nodes of fire protection system
Fire pump suction pipe and outlet pipe: The rising stem gate valve is used first for intuitive monitoring of the status, and the concealed stem gate valve is suitable for buried or concealed installation.
Fire water supply network: It is installed in the main pipe to control the water flow in different areas, and cooperates with fire hydrants to achieve rapid cutoff.
Pressure stabilization system: The suction/discharge pipe of the pressure stabilization pump needs to use an open-stem gate valve to ensure reliability and ease of operation.
Working condition adaptation
Indoor overhead pipelines usually use open-stem gate valves, while outdoor buried pipelines tend to use a concealed-stem design.
5. Precautions
Installation requirements: The verticality of the valve stem must be ensured to avoid gate blockage due to deflection; a special valve well must be configured for corrosion protection when buried.
Maintenance points: Regularly check the wear of the sealing surface, clean the impurities in the valve cavity, and the open-stem gate valve needs to lubricate the exposed part of the valve stem.
Fire hydrant gate valves have become the core components in the fire protection system to ensure water supply reliability through rigid sealing and structural adaptability.
