Two-piece ball valves and three-piece ball valves differ significantly in structure and features. As a professional valve supplier, GNEE Group will explain the differences between these two types of valves. GNEE Group is a leading valve manufacturer in China.Valve Performance Guarantee – Learn More Today!
Two-Piece Ball Valve Structure
A two-piece ball valve consists of a main valve body and a secondary valve body, hence the name. It is a commonly used type of ball valve. After the ball, seat, and stem are installed in the main valve body, the secondary valve body is connected to the main valve body via threads or bolts. Its ball core flow channel is full-bore, resulting in low flow resistance and high flow capacity.
Two-piece ball valves also come in internal thread, external thread, and both internal and external thread connections. The threads typically use 55° tapered pipe threads for good sealing. Two-piece flanged ball valves are widely used.
Features of Two-Piece Ball Valves
Two-piece ball valves offer full-bore operation, reducing flow resistance and increasing flow capacity, making them suitable for various pressure and diameter applications. The two-piece ball valve consists of a main valve body and a secondary valve body. The main valve body contains the ball, seat, and stem, while the secondary valve body is connected to the main valve body via threads or bolts. This design allows the ball core flow channel to reach full bore size, thereby reducing flow resistance and significantly improving flow capacity.
Two-piece ball valves are suitable for both normal and high-pressure environments, and can also be used in non-standard nominal diameter applications smaller than DN50.
Three-piece ball valve structure
The three-piece ball valve body consists of one main valve body and two auxiliary valve bodies, hence the name. After the ball core and valve stem are installed in the main valve body, the auxiliary valve bodies are installed in the valve seats, and the main and auxiliary valve bodies are connected as a single unit by bolts. Its ball core flow channel is also full bore size.
Three-piece ball valves also have internal thread connections and external thread connections. The internal thread typically uses a 55° tapered pipe thread, providing good sealing performance. The external thread has a weld joint, allowing welding to pipelines. Disassembly and assembly are more convenient during maintenance, avoiding the need for a separate union for internal thread connections.
Butt welding and socket welding connections are also possible, and extended pipe welding can be used to avoid high-temperature damage to the valve seat seal ring and valve stem packing during welding, reducing installation difficulty.
Features of Three-Piece Ball Valves
Three-piece ball valves feature a full-bore design and superior online maintainability, offering convenient disassembly and simplified maintenance procedures. The structure of a three-piece ball valve is similar to that of a two-piece ball valve, consisting of a main valve body and two auxiliary valve bodies. The ball and stem are installed inside the main valve body, while the auxiliary valve bodies are connected to the valve seats, and the main and auxiliary valve bodies are tightly connected as a single unit by bolts. This design allows the ball flow channel of the three-piece ball valve to also achieve a full-bore size, ensuring smooth fluid flow.
Another major advantage of three-piece ball valves is their convenient online maintenance function. By loosening the screws on the valve body and removing one bolt passing through the main valve body, the main valve body can be easily rotated, allowing for replacement of the valve seat seal. For further repairs, the bolts on the main valve body can even be completely removed, allowing the main valve body to be disassembled for maintenance, while the auxiliary valve bodies remain on the pipeline, eliminating the need to disassemble the entire ball valve and greatly simplifying the maintenance process.
The main differences between two-piece and three-piece ball valves:
- Structurally: Two-piece and three-piece ball valves have significantly different structures. A two-piece ball valve has only one ball and one seat, while a three-piece ball valve has two seats and one ball.
- Installation and maintenance: Two-piece ball valves cannot be maintained online and must be shut off. Three-piece ball valves, on the other hand, are easier to maintain online.
- Applicable scenarios: Two-piece ball valves are suitable for applications that do not require online maintenance, such as low-pressure liquid control systems. Three-piece ball valves are suitable for control systems that require online maintenance.
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