Five Main Types Of Butterfly Valve End Connection Types

The end connection of a butterfly valve is the interface between it and the pipe, directly impacting the valve's installation efficiency, sealing performance, and applicable scenarios. There are five common butterfly valve end connection types: flange, wafer, weld, clamp, and threaded. Choosing the right connection type ensures the valve's reliable operation; choosing the wrong one can lead to leaks, at best, or even disrupt the entire system.

1. Flange connection: The most common type.

Connecting to the pipe via a flange and securing with bolts, this connection is suitable for medium-, high-, and large-diameter pipes, offering excellent sealing and easy installation. This connection can withstand high pressures and can be used for everything from low-pressure water pipes to medium-pressure steam pipes. It's often used on acid and alkali pipes in chemical plants because a gasket on the flange surface provides a reliable seal and facilitates later disassembly and inspection. However, it does have a minor drawback: it takes up space. The flange and bolts require ample clearance for the pipe.

2. Wafer connection: This significantly saves space.

This type of butterfly valve is secured by clamping the valve body's ends together with pipe flanges. It features a compact, lightweight design and is suitable for medium- and low-pressure, large-diameter pipes. However, it places high demands on flange parallelism and uniform clamping force. A butterfly valve has no flanges; it consists of a thin body. During installation, it is clamped between two pipe flanges and bolted directly through them. Water treatment plants often use this type of valve for large-diameter pipes, saving material and being lightweight, making it easy for workers to lift and install. However, it requires high flange parallelism. If the flanges are misaligned, tightening the bolts can easily deform the valve body, exacerbating leakage.

3. Welded connections: These are considered "permanent connections."

They are available in socket welds (for small diameters and high pressures) and butt welds (for large diameters and high pressures and temperatures). They offer excellent sealing properties and are suitable for high-pressure, high-temperature, or corrosive media, but they can be difficult to maintain. Directly welding the butterfly valve's ends to the pipe eliminates gaps between the bolts and flanges, ensuring impeccable sealing. This type of valve is often chosen for high-temperature and high-pressure applications, such as steam pipes in power plants. However, once welded, it's difficult to remove. If you want to replace the valve or perform maintenance, you must first cut the weld. This connection is suitable for pipes that won't be touched for extended periods.

4. Threaded connection: Suitable for small-diameter butterfly valves.

The valve body directly screws onto the pipe thread. This connection is only suitable for small-diameter (usually DN 50 or less) and low-pressure applications, such as household water systems. Installation is simple, but pressure resistance is limited. The valve has internal or external threads on both ends and can be screwed directly onto the pipe, much like connecting a faucet at home. This connection is often used for small pipes before and after water meters, offering quick installation without the need for large tools. However, the threads are susceptible to corrosion. If the pipe carries acids or alkalis, the threads can rust over time, making removal difficult. Therefore, it is generally used only for low-pressure, normal-temperature, fresh water pipes.

5. Clamp connection: A relatively recent development.

Clamps secure the valve body. This connection is suitable for quick-install, low-pressure pipes (such as fire protection and temporary municipal pipes). While more expensive, it's convenient. Butterfly valves have ferrules on both ends, and a dedicated clamp secures the pipe connection for a single-tight fit. Food and pharmaceutical factories favor them because they're quick to assemble and disassemble, allowing for quick disassembly for pipe cleaning and meeting hygiene requirements. However, the strength of the clamp is limited, and it can't hold pipes under excessive pressure. It's generally only used in applications below 1.6 MPa.

Which connection should you choose? Consider three factors: the pipe pressure, the diameter, and whether it requires frequent disassembly. For high pressure, choose flanges or welding. For larger diameters, opt for clamps for ease. For smaller diameters, opt for threads. For more demanding hygiene requirements, opt for clamps. Only with the right connection can a butterfly valve perform its intended function effectively within the pipe.