Flexible Butterfly Valve vs. Metal Butterfly Valve
The butterfly valve has a wide range of applications. It is generally installed in pipelines that transport various corrosive and non-corrosive fluid media, including gas, natural gas, liquefied petroleum gas, hot and cold air, chemical fusion, and other engineering systems for regulation. There are many types of butterfly valves, and each type has different uses. Butterfly valves are classified according to the sealing form and can be divided into tight-sealing/flexible base butterfly valves and solid/metal base butterfly valves. Despite the difference of only one word between the two types of butterfly valves, they are completely different in terms of structural materials and application fields. This article will analyze the differences between the flexible butterfly valve and the metal butterfly valve.
The main difference between the flexible butterfly valve and the metal butterfly valve lies in the sealing surface:
The sealing sides of the flexible butterfly valve are made of metallic materials on one side and flexible non-metallic materials on the other side, generally rubber or tetrafluoroethylene plastic. The combination of these sealing materials allows the flexible butterfly valve to have good sealing performance, but it is not resistant to high temperatures, susceptible to corrosion, and has a short service life.
Both sides of the seal pair of the metal butterfly valve are made of metallic materials. The metal-to-metal sealing makes the sealing performance of the metal butterfly valve natural, and it is resistant to high temperatures, pressure, and corrosion, with a long service life.
The seat of the soft-sealing butterfly valve is made of rubber or tetrafluoroethylene plastic. It boasts excellent closing performance and can achieve leak-free sealing. However, it has a relatively short service life and is not resistant to high temperatures. It is also not suitable for some pipelines with highly corrosive media. The sealing seat of the metal butterfly valve is made of metal material, and its sealing performance is also excellent.
In addition to the difference in the sealing surface, the difference between the flexible butterfly valve and the metal butterfly valve is as follows:
Flexible butterfly valves are mostly of the centerline type. Metal butterfly valves can be single, double, or triple offset.
Flexible butterfly valves are suitable for normal temperature environments. Metal butterfly valves adapt well to low temperatures, normal temperatures, and high-temperature environments.
Flexible butterfly valves are suitable for low pressure and normal pressure environments. Metal butterfly valves are not only suitable for low pressure and normal pressure but also suitable for medium and high-pressure working environments.
As mentioned above, the sealing performance of the flexible butterfly valve is better than that of the metal butterfly valve. However, now, in order to adapt the metal butterfly valve to more demanding working conditions, it has a special process.
Flexible butterfly valves are suitable for opening and closing ventilation pipelines, dust removal in both directions, water treatment, light industries, petroleum, chemical, and other industries. Metal butterfly valves are mainly used in heating, gas, oil, acid, alkali, and other environments.
Flexible Butterfly Valve:
- Construction: A flexible butterfly valve typically consists of a circular disc or plate with a shaft passing through its diameter. The disc is made of a flexible material, such as rubber or fluoropolymer, which allows it to deform and create a seal against the valve seat when closed.
- Operation: The disc rotates on the shaft to control the flow of fluid. When the valve is fully open, the disc is perpendicular to the flow direction, allowing unrestricted flow. When the valve is closed, the disc rotates to a position parallel to the flow direction, creating a seal and blocking the flow.
- Advantages: Flexible butterfly valves offer good sealing performance, quick operation, and a compact design. They are suitable for low-pressure and normal temperature applications where resistance to corrosion is not a critical factor.
- Limitations: These valves may not be suitable for high-pressure or high-temperature applications due to the limitations of the flexible materials. They may also be prone to wear and tear over time.
Metal Butterfly Valve:
- Construction: A metal butterfly valve features a metal disc or plate with a shaft passing through its diameter. The disc is rigid and typically made of materials such as cast iron, stainless steel, or bronze. The valve body and seat are also made of metal.
- Operation: Similar to the flexible butterfly valve, the metal butterfly valve controls flow by rotating the disc. The disc can be positioned perpendicular to the flow for full flow or parallel to the flow for closure.
- Advantages: Metal butterfly valves are known for their durability, resistance to high temperatures and pressures, and excellent resistance to corrosion. They have a longer service life compared to flexible butterfly valves.
- Limitations: Metal butterfly valves may be bulkier and require more space compared to flexible ones. They may also be slower to operate than flexible valves due to the rigid disc construction.
- It’s important to consider factors such as fluid characteristics, pressure, temperature, corrosion resistance, and application requirements when selecting between flexible and metal butterfly valves. Consulting with a specialized engineer can help determine the most suitable type for your specific application.
