1. Basic structure and working principle of gate valve
The basic structure of the gate valve includes valve body, valve plate, valve seat, valve stem and sealing ring. Its working principle is to cut off the pipeline fluid through the up and down movement of the gate plate. The opening and closing of the gate valve is completed by rotating the valve stem to drive the gate plate to move up and down. When the valve is in a fully open or fully closed state, the flow of the fluid is almost unimpeded.
Unlike other types of valves, the gate valve has no obvious flow regulation ability when it is opened, and it is more suitable for fully open or fully closed operations.
2. Key factors to consider when purchasing gate valves
1. Media type
When choosing a gate valve, the properties of the medium, such as liquid, gas or steam, etc., must be considered first. If it is a corrosive medium (such as acid, alkali, seawater, etc.), it is necessary to select valve materials with corrosion resistance, such as stainless steel, alloy steel, etc. For high temperature and high pressure media, it is necessary to select high temperature and high pressure resistant materials and designs.
2. Working pressure and temperature
The working pressure and temperature range of the gate valve determine the choice of its material and structure. Common gate valve working pressures include PN10, PN16, PN25, PN40, etc. The specific selection should be determined according to the pressure level of the pipeline system. In terms of temperature, for high temperature applications (such as boiler systems, steam pipelines), the material and sealing performance of the gate valve need special attention.
3. Valve body material
The materials of gate valves are usually divided into:
- Cast iron: Suitable for low-pressure media such as general water and sewage.
- Carbon steel: Suitable for general liquid and gas pipelines, but not suitable for corrosive media.
- Stainless steel: Suitable for corrosive liquids, chemicals, etc., with excellent corrosion resistance.
- Alloy steel: Suitable for high temperature and high pressure environments, with strong high temperature resistance.
4. Sealing method
There are usually two sealing methods for gate valves: hard sealing and soft sealing.
- Hard sealing gate valve: The sealing surface is made of metal materials, suitable for high temperature, high pressure, and highly corrosive media.
- Soft sealing gate valve: The sealing surface is made of rubber, polytetrafluoroethylene (PTFE) and other materials, suitable for low temperature, low pressure and general fluid applications, with good sealing performance.
5. Valve structure
The structure of the gate valve can be selected according to the use environment and pipeline characteristics:
- Straight-through type: Suitable for general pipeline installation.
- Rising stem type: The valve stem will rise during operation, suitable for occasions with limited space.
- Non-rising stem type: The valve stem does not rise, suitable for pipeline systems with narrow sites.
6. Connection method
Common connection methods for gate valves are:
- Flange connection: Suitable for large-diameter, high-pressure pipelines, easy to install and disassemble.
- Threaded connection: Suitable for small-diameter pipelines, simple to install, but weak pressure bearing capacity.
- Clamp connection: Suitable for small and medium-diameter pipelines, easy to install, suitable for some small pipeline systems.
7. Drive method
Gate valves are usually driven by manual, electric, pneumatic and other methods:
- Manual drive: Commonly used for small valves or occasions where operation is not frequent, with low cost.
- Electric drive: Suitable for occasions with a high degree of automation and can achieve remote control.
- Pneumatic drive: Suitable for occasions with frequent opening and closing or requiring rapid response, which can improve operating efficiency.
8. Valve size and diameter
Select the appropriate gate valve size according to the diameter, flow rate and system requirements of the pipeline. Too large a size will cause waste of resources, and too small a size will not meet the flow requirements.
9. Operation requirements
When purchasing, choose the appropriate drive mode and control device according to the operating frequency, whether remote control is required, and whether automatic control is required. If frequent opening and closing or precise control is required, you may need to choose an electric or pneumatically driven gate valve.
3. Common applications of gate valves
Gate valves are widely used in the following fields:
1. Water supply system: used in municipal water supply, industrial water supply and other pipelines to cut off and isolate fluids.
2. Oil and natural gas: used for fluid control of oil and gas pipelines, especially in high pressure and high temperature environments.
3. Chemical industry: used for isolation, regulation and control of chemical reaction equipment.
4. Power industry: used for flow control and cutoff of boilers and steam systems.
5. Sewage treatment: used for pipeline fluid control of sewage treatment plants.
4. Selection case of gate valves
Suppose an oil company needs to purchase gate valves for oil and gas pipelines, requiring high temperature resistance, high pressure resistance, and the ability to withstand harsh environments. When selecting a valve, you should focus on the following:
- Material selection: Choose carbon steel or alloy steel to ensure the valve's high pressure and high temperature resistance.
- Sealing method: Choose a hard-sealed gate valve to ensure sealing performance under high temperature and high pressure conditions.
- Drive method: Choose a pneumatic drive method to facilitate quick opening and closing operations.
- Flange connection: Choose a flange connection to ensure that the valve can withstand greater pressure and is easy to install.
5. Conclusion
When purchasing a gate valve, you need to consider a variety of factors, including media type, working pressure, temperature requirements, valve body material, sealing method, connection form, etc. By clarifying the application and needs and choosing the right type of gate valve, you can ensure the safety of the pipeline system and the reliability of flow control. At the same time, choosing the right drive method and operation method will improve the working efficiency of the valve and the automation level of the system.