1. Basic types and structures of ball valves
The basic working principle of the ball valve is to control the flow of fluid by rotating a ball with an aperture on the valve seat. When the hole of the ball is consistent with the fluid flow direction of the pipeline, the fluid can pass; when the ball rotates 90 degrees, the fluid flow is completely cut off. According to different design requirements, ball valves can be divided into several main types:
1. Floating Ball Valve Floating ball valve is the most common type of ball valve, whose ball is not fixed and floats. When the valve is closed, the ball is pushed to the valve seat by the fluid pressure to ensure sealing. This type of ball valve is suitable for small and medium-sized pipeline systems with low to medium pressure.
2. Trunnion Mounted Ball Valve
The trunnion mounted ball valve has support devices (called "trunnion") on both sides of the ball, which can withstand greater fluid pressure. Because the ball is fixed, the sealing performance is better, and it is usually used in large-diameter, high-pressure occasions. The fluid resistance of the trunnion mounted ball valve is low, and it is suitable for high-flow, high-pressure pipeline systems.
3. Three-Way Ball Valve
There are three channels on the ball of the three-way ball valve, which allows the fluid to flow in multiple directions. This type of ball valve is often used in occasions where fluid flow direction switching or distribution is required, such as liquid flow distribution, mixing and other systems.
4. V-Port Ball Valve
The V-port ball valve is a ball valve with a V-shaped port cut on the ball, which can provide more precise flow regulation. It is suitable for occasions where flow regulation is required, especially in the process of controlling flow changes, the V-port ball valve can better control the fluid flow.
5. Electric ball valve and pneumatic ball valve
Electric ball valve and pneumatic ball valve are usually important parts of the automation control system. The opening and closing operation of the ball valve can be realized by electric or pneumatic drive. This valve is often used in pipeline systems that require remote control or automatic operation.
2. Key factors for purchasing ball valves
When purchasing ball valves, the following factors are very important:
1. Media type
The selection of ball valves needs to select appropriate materials and sealing methods according to the type of media controlled. Common media are:
- Water: You can choose ball valves made of cast iron, carbon steel, stainless steel and other materials, and usually do not require high corrosion resistance.
- Gas: It is usually necessary to choose ball valves made of carbon steel or stainless steel to ensure that they can withstand high pressure.
- Oil: For oil media, stainless steel or alloy steel ball valves are usually selected to ensure their sealing and corrosion resistance.
- Chemicals: For acid, alkali, and corrosive media, choose corrosion-resistant ball valves, usually stainless steel, alloy steel or special coating ball valves.
2. Working pressure and temperature
The working pressure and temperature range of the ball valve directly determine its applicable occasions. According to the pressure and temperature conditions of the fluid medium, select the appropriate ball valve material and design.
- Normal temperature and pressure: Ordinary carbon steel, cast iron or stainless steel ball valves can meet the requirements.
- High pressure: You need to select a fixed ball valve (trunnion mounted) or a high-pressure design ball valve to ensure its pressure resistance.
- High temperature: For high temperature environments, select ball valve materials with high temperature resistance, such as high-temperature alloys, stainless steel, etc.
3. Sealing performance
The sealing performance of the ball valve is a key factor in selection. Ball valve sealing methods usually include soft sealing and hard sealing:
- Soft sealing: Use soft materials (such as PTFE) as the sealing surface, suitable for low to medium pressure and normal temperature occasions. Good sealing, suitable for water, oil and other media.
- Hard sealing: Use metal materials as the sealing surface, suitable for high pressure, high temperature or highly corrosive media. Metal seals are more wear-resistant and suitable for high pressure, oil, natural gas and other industries.
4. Flow Control Accuracy
Ball valves are suitable for on-off operation, but some ball valves (such as V-type ball valves) have good flow regulation function and are suitable for precise flow control. The V-shaped opening on the V-type ball valve allows the fluid to flow gradually during the opening process of the ball, so it is particularly suitable for applications where flow is regulated and controlled.
5. Valve Material and Corrosion Resistance
It is very important to choose the right ball valve material according to the corrosiveness of the medium and the working environment. Common materials include:
- Carbon Steel: Suitable for low-corrosive environments and relatively economical prices.
- Stainless Steel: Suitable for highly corrosive media, especially in the chemical and pharmaceutical industries.
- Alloy Steel: Suitable for high temperature and high pressure environments, and can withstand extreme working conditions.
- Plastic: For non-corrosive media such as water and certain chemicals, plastic ball valves have good corrosion resistance.
6. Drive Mode
The drive modes of ball valves include manual, electric, pneumatic, etc. When choosing the drive mode, you need to choose according to the actual working conditions:
- Manual: Suitable for small systems or occasions where manual operation is required.
- Pneumatic: Suitable for remote control occasions, can quickly open or close the ball valve.
- Electric: Suitable for occasions that require precise control and remote automatic operation.
7. Size and connection method
The size of the ball valve should be selected according to the diameter and flow requirements of the pipeline. Common connection methods are:
- Flange connection: Suitable for large-diameter pipelines, good sealing and easy installation.
- Threaded connection: Suitable for small-diameter pipelines, simple installation and low cost.
- Welding connection: Suitable for pipeline systems that require high sealing and high pressure.
3. Common applications of ball valves
Due to their excellent sealing, high pressure resistance and easy operation, ball valves are widely used in the following fields:
1. Oil and gas: Ball valves are used in oil and gas pipeline systems, especially in high pressure and high flow situations, to provide efficient flow control.
2. Chemical industry: In the transportation and production of chemicals, ball valves are used to control the flow of corrosive media.
3. Water treatment: used in water supply systems and sewage treatment processes, ball valves are used for flow switch control and regulation.
4. Food and beverage: ball valves are widely used in the food and beverage industry, especially in the production process that requires high sealing and hygienic fluid control.
5. Heating, ventilation and air conditioning (HVAC): used for fluid control in HVAC systems, especially in high pressure and large flow situations, to ensure stable operation of the system.
6. Pharmaceutical industry: In pharmaceutical production, ball valves are used to control the flow of pharmaceutical liquids and gases to ensure the quality and production process of pharmaceuticals.
4. Selection case
Suppose a factory needs to purchase ball valves to control the flow of high-temperature oil flow on the production line, and the ball valves are required to be resistant to high temperatures and have good sealing. The following selections can be considered:
- Material selection: Use stainless steel or high-temperature alloy steel ball valves to ensure high temperature resistance.
- Type selection: Choose a fixed ball valve (trunnion mounted), which can withstand high pressure and is suitable for large flow.
- Sealing method: Choose a metal hard seal to ensure sealing in a high temperature environment.
- Drive mode: If automated operation is required, pneumatic or electric ball valves can be selected to ensure the accuracy of fluid control and the convenience of remote operation.
- Connection mode: According to the pipeline size and installation requirements, flange connection or welding connection can be selected to ensure that the valve is firmly installed and has good sealing.
5. Conclusion
When purchasing a ball valve, the key is to reasonably select the type, material, sealing method, size and drive method of the valve according to the actual working conditions. The advantages of ball valves include fast switching, good sealing, low fluid resistance, and are suitable for a wide range of fluid control needs. By understanding the characteristics and working principles of different types of ball valves, and selecting suitable ball valves according to factors such as media type, working pressure, and temperature, the stable and safe operation of the fluid control of the pipeline system can be effectively guaranteed.