What Is A Closed Gate Valve?

A Block Valve is a valve used to completely cut off or isolate the flow of fluid and is widely used in industrial pipeline systems.

Definition and Function
Definition: A Block Valve is a valve that controls the flow of fluid through the lifting and lowering movement of the gate. When the gate is fully raised, the valve is fully open; when the gate is fully lowered, the valve is fully closed, achieving complete cutoff of the fluid.
Function:
Cut off the fluid: In situations where the flow of fluid needs to be completely stopped, such as during equipment maintenance, pipeline inspection, or in emergencies, the Block Valve can reliably cut off the fluid.
Isolate the system: Used to isolate different parts of the pipeline system to facilitate local repair or replacement of equipment.
Structure and Working Principle
Main Structure:
Valve Body: Bears fluid pressure and connects pipelines.
Gate: Perpendicular to the flow direction of the fluid, controls the on and off of the fluid through lifting and lowering movements.
Valve Stem: Connects the gate and the handwheel (or actuator) to transmit operating force.
Seal: Ensures the sealing performance of the valve when it is closed to prevent leakage.
Working Principle:
Open: Rotate the handwheel; the valve stem drives the gate to rise, and the fluid channel opens.
Close: Rotate the handwheel in the opposite direction; the valve stem drives the gate to descend, the gate fits tightly with the valve seat, and the fluid channel closes.
Features and Advantages
Complete Cut-off: When the gate valve is closed, there is no gap between the gate and the valve seat, achieving complete cut-off of the fluid.
Low Fluid Resistance: When the gate valve is fully open, the fluid channel is straight-through, with low fluid resistance, suitable for large flow and low pressure loss.
Simple Structure: Simple design, easy to manufacture and maintain.
Wide Range of Application: Can be used for various media, such as water, steam, oil, gas, etc.
Classification
According to the Gate Structure:
Wedge Gate Valve: The gate is wedge-shaped, suitable for high pressure and high temperature occasions.
Parallel Gate Valve: The gate is a parallel plate, suitable for low pressure and large diameter occasions.
According to the Driving Mode:
Manual Gate Valve: Operated by handwheel.
Electric Gate Valve: Operated by electric actuator.
Pneumatic Gate Valve: Operated by pneumatic actuator.
According to the Sealing Surface Material:
Hard Seal Gate Valve: The sealing surface is made of metal material, suitable for high temperature and high pressure occasions.
Soft Seal Gate Valve: The sealing surface is made of soft materials such as rubber and plastic, suitable for normal temperature and low pressure occasions.
Application Field
Petrochemical: Used to cut off crude oil, natural gas, chemical media, etc.
Power Industry: Used for cutting off boiler feed water and steam pipelines.
Water Treatment: Used for isolation of urban water supply and sewage treatment systems.
Metallurgical Industry: Used for cutting off high temperature and high pressure media.
Shipbuilding: Used for isolation of ship pipeline systems.
Precautions
Installation Direction: Gate valves usually have no flow direction requirements, but some specially designed gate valves may have flow direction requirements and need to be installed according to the instructions.
Operating Torque: Large-diameter gate valves have a large operating torque and need to be equipped with a suitable actuator.
Sealing Performance: Check the seals regularly to ensure the sealing performance when the valve is closed.
Maintenance: Lubricate the valve stem regularly to prevent rust and ensure flexible valve operation.
Comparison with Other Valves
Compared with Stop Valve:
Gate Valve: Small fluid resistance, suitable for large flow occasions; but the opening and closing time is longer.
Stop Valve: Large fluid resistance, suitable for small flow and high pressure occasions; short opening and closing time.
Compared with Ball Valve:
Gate Valve: Simple structure, easy maintenance; but relatively poor sealing performance.
Ball Valve: Good sealing performance, easy operation; but large fluid resistance, suitable for small diameter occasions.