Butterfly Valves - Process Valves

When it comes to controlling the flow of fluids in industrial processes, butterfly valves are often the go-to choice. But how much do you really know about these crucial process valves?

Butterfly Valve Function

Butterfly valves consist of a rotating disc or plate that is positioned in the middle of the pipe to regulate the flow. When the disc is parallel to the flow, it allows for maximum fluid passage, while when it is perpendicular, it restricts the flow. Butterfly valves are commonly used in industries such as water treatment, power generation, and chemical processing.

The primary function of a butterfly valve is to regulate the flow of fluids in a pipeline. By adjusting the angle of the disc, operators can control the rate at which the fluid flows through the valve. This allows for precise control and adjustment of flow rates, making butterfly valves highly versatile in various applications.

Butterfly valves are known for their quick and efficient operation. With just a quarter-turn of the disc, the valve can go from fully open to fully closed position. This rapid action makes butterfly valves ideal for systems that require frequent start-stop operations or quick adjustments to flow rates. It also reduces the chances of fluid hammer or pressure surges in the pipeline.

Butterfly valves offer excellent sealing capabilities, ensuring that there is minimal leakage when the valve is closed. The disc typically comes in contact with a resilient sealing material, such as rubber or elastomer, creating a tight seal. This versatility means butterfly valves can handle a wide range of fluids, including liquids, gases and slurries. They can be used in both low-pressure and high-pressure systems, as well as in applications with corrosive or abrasive fluids or applications where leakage prevention is critical, such as in hazardous fluid handling.

Butterfly valves are lightweight and compact, making them easy to install and maintain. Their simple design consists of fewer parts compared to other valve types, reducing the chances of mechanical failure or breakdown. This simplicity also makes butterfly valves cost-effective and efficient, as they require less space and effort for installation and maintenance.

Butterfly valves are designed to be bi-directional, meaning they can handle flow in either direction. This feature eliminates the need for specific orientation during installation, simplifying the piping layout and reducing installation time. It also allows for easy system maintenance and troubleshooting, as the valve can be operated in reverse to flush out any debris or blockages.

Butterfly valves are designed to withstand various operating conditions, including high pressures, high temperatures, and corrosive environments. They are often made from materials such as cast iron, carbon steel, stainless steel, and exotic alloys to ensure durability and resistance against wear and corrosion. Different seat materials, such as rubber, PTFE, or metal, may be used to provide a tight seal and prevent leakage. The disc of a butterfly valve can be made from metal, elastomer, or a combination of both, depending on the application requirements. Different types of actuators can also be selected to suit the automation and control requirements of the system. This customization flexibility makes butterfly valves adaptable to a wide range of applications.

Butterfly Valve Types

To ensure that you choose the right butterfly valve for your project, it’s essential to familiarize yourself with the different types available. Each type has its advantages and limitations and selecting the wrong type could result in inefficient flow control or even valve failure.

Butterfly valves come in four main types: concentric, double eccentric, triple eccentric, and wafer type.

The concentric butterfly valve is the most common type and is widely used in various industries. The double eccentric butterfly valve has a disc that is offset from the centreline of the valve body, which reduces friction and wear and the triple eccentric butterfly valve has a disc that is offset and inclined, providing a tight seal with minimal leakage. The wafer-type butterfly valve is compact and lightweight, making it suitable for applications with limited space.

Each type of butterfly valve has its advantages and disadvantages.

The concentric butterfly valve is cost-effective and easy to install, but it may not be suitable for high-pressure applications. The double eccentric butterfly valve offers better sealing performance and is suitable for high-pressure and high-temperature applications. However, it is more expensive than the concentric type. The triple eccentric butterfly valve provides excellent sealing performance and is ideal for critical applications that require zero leakage. However, it is the most expensive type of butterfly valve. The wafer-type butterfly valve is affordable and easy to install, but it may not withstand high pressures.

When selecting a butterfly valve, several factors need to be considered, such as the type of fluid being handled, the pressure and temperature conditions, the required flow rate, and the system requirements. It is important to choose the right type and size of butterfly valve to ensure proper operation and optimal performance. Proper installation, maintenance, and periodic inspection are also essential to ensure the longevity and reliability of butterfly valves. Regular maintenance, such as lubrication and sealing checks, is necessary to prevent leakage and ensure smooth operation.

Butterfly Valve Operation

Unlike other types of valves that require multiple turns of a handle or actuator, a butterfly valve can be fully opened or closed with just a quarter turn. This makes butterfly valves ideal for applications where fast and precise control of fluid flow is required. Butterfly valves are available manually operated or via an actuator. 

Manual Butterfly Valve

Manual butterfly valves are operated by turning a handle or a handwheel. When the handle or handwheel is rotated, the disc inside the valve rotates as well, either opening or closing the valve. The disc is connected to a shaft, which is turned by the handle or handwheel. This rotation allows for the regulation of flow by adjusting the position of the disc.

Actuated Butterfly Valve

Actuated butterfly valves are available with several different types of actuators including pneumatic, electric, electro-pneumatic and hydraulic. For now, we will just focus on the pneumatic and electric-actuated butterfly valves.

To understand how an electrically actuated butterfly valve operates, imagine a device that uses electricity to move a disc within a pipe. This disc, known as the butterfly valve, controls the flow of fluid or gas passing through the pipe. When electricity is supplied, the valve opens or closes by rotating the disc. The benefit of this system is that it allows for precise control of the flow rate and direction. However, the drawback is that it relies on a power source and may be more expensive to install and maintain compared to other types of valves.

On the other hand, a pneumatically actuated butterfly valve operates using air pressure. When compressed air is applied, it moves a piston or diaphragm that in turn rotates the disc. This type of valve is commonly used in industries where electricity is not readily available or in hazardous environments where electrical sparks could be dangerous. The advantage of a pneumatic valve is its simplicity and reliability. However, it may not offer the same level of control as an electrically actuated valve and requires a source of compressed air.

Both types of butterfly valves have their pros and cons. Electrically actuated valves provide precise control but require an electrical power source and can be more expensive. Pneumatically actuated valves are reliable and suitable for certain environments, but may not offer the same level of control. It is important to consider the specific needs and requirements of the application when choosing between these two options.

Conclusion

In conclusion, butterfly valves are an essential component in various industries, ensuring smooth and efficient processes. Their versatility, reliability, and cost-effectiveness make them a go-to choice for many businesses. So, if you’re looking for a valve that can handle high flow rates, tight shut-off, and easy maintenance, look no further than the butterfly valve.