I. Basic Concepts and Core Principles
1. Definition and Structure
A wafer type check valve is a type of valve that automatically opens and closes in response to the flow of the medium. Its body is designed in the shape of a thin wafer, which is easily clamped between two flanges using bolts, allowing it to fit without taking up additional space in the pipeline.
Key Components:
Valve Disc: The disc can either swing freely around a shaft or guide rail or slide along the axis, effectively controlling the unidirectional flow of the medium.
Valve Body: The body is typically made from materials such as cast iron, stainless steel, or carbon steel, and its surface can be treated to provide anti-corrosion properties.
Sealing surface: Made of rubber, metal, or composite materials to ensure a tight seal when closed.
2. Working Principle
Open state: When the medium flows in the forward direction, it pushes the valve disc to open against gravity or spring force, with relatively small resistance, allowing the medium to pass through.
Closed State: When the medium ceases to flow or begins to flow in the opposite direction, the valve disc closes rapidly due to gravity, the pressure of the backflowing medium, or the force of a spring. This action prevents backflow.
Core Function: The primary function of the wafer type check valve is to prevent the backflow of the medium in the pipeline. This helps to protect pumps, compressors, and other equipment from damage and ensures the proper functioning of the system process.
Ii. Main Types and Characteristics
1. Classify by material
Metal material:
Cast iron: Low cost, suitable for non-corrosive media such as water and air.
Stainless steel: Corrosion-resistant, used in chemical, food, seawater, and other scenarios.
Carbon steel/alloy steel: Resistant to high pressure and high temperature, suitable for steam, oil, and natural gas pipelines.
Non-metallic material:
Plastic: Resistant to acids and alkalis, lightweight, and used in water treatment and chemical pipelines.
Rubber-Lined and Fluorine-Lined Valves: The inner lining of the metal valve body is constructed from corrosion-resistant materials, making it suitable for handling strongly corrosive media.
2. Classification by Sealing Method
Soft Sealing: The valve disc or seat is made from materials such as rubber and PTFE, which provide excellent sealing performance. These valves are ideal for low-pressure applications, at normal temperatures, and for use with corrosive media.
Hard seal: Metal-to-metal seal, resistant to high temperature and high pressure, wear-resistant, used in high-temperature steam, oil products, and other working conditions.
Iii. Key Points for Selection and Installation
1. Key parameters for selection
Nominal diameter and pressure rating: Match the pipe size and design pressure. For high-pressure scenarios, thick-walled valve bodies should be selected.
Medium characteristics:
Corrosive media: Select stainless steel, fluorine-lined, or plastic materials.
For media containing particles: Select swing or Y-type check valves to prevent the lift-type valve disc from getting stuck.
Flow direction and installation space: For wafer type, flange spacing should be reserved. Shorter structures are preferred to save space.
2. Installation precautions
Correct direction: The arrow marking on the valve body must be consistent with the flow direction of the medium. Reverse installation will cause the valve to fail.
Flange matching: Use flanges that match the pressure rating of the valve. Bolts should be tightened evenly to prevent leakage or deformation of the valve body.
Avoid shock: It is recommended to series buffer devices in large-diameter pipelines to reduce the water hammer effect when the valve disc closes.
Maintenance space: Sufficient space should be reserved for disassembling the valve disc for inspection, especially for spring-type or lift-type structures.
Summary
The wafer type check valve, with its advantages of compact structure, convenient installation, and low cost, has become a core component for preventing the backflow of media in industrial pipelines.
