Differences between 1-PC, 2-PC and 3-PC Ball Valves

Differences between 1-PC, 2-PC and 3-PC Ball Valves

Here are the differences between 1-PC ball valves, 2-PC ball valves and 3-PC ball valves.

1.  Structure and characteristics of the 1-PC ball valve

The 1-PC ball valve is called a one-piece ball valve because the valve body adopts an integral structure. Its appearance is small and its weight is light. The ball core, valve seat, and valve stem are installed from the flow channel on one side of the valve body. Due to limitations in the flow channel size of the valve body, the full diameter ball core cannot be installed inside the valve body, so the flow channel of the one-piece ball valve ball core is reduced. The circulation capacity is subject to certain limitations. There is a certain cost advantage. It is mainly used for low-pressure pipelines.

One-piece ball valves have threaded connections, flange connections, and wafer connections. Threaded 1-PC ball valves typically use 55 degrees taper pipe threads to achieve better sealing performance. The installation of flange connections is relatively convenient. The clamp connection structure has a short length and can be installed on compact space pipelines. The valve is made of WCB cast steel, stainless steel CF8, CF8M, and other materials.

The 1-PC threaded ball valve is mostly used in low-pressure pipelines due to the shallower valve stem packing chamber and less sealing packing added. The one-piece flange ball valve is made into a high-temperature sewage ball valve, which can effectively prevent media leakage from the valve body and avoid the risk of media leakage between the 2-PC and 3-PC ball valves. It can be used for steam and heat transfer oil media. It can also be made into an insulated ball valve to transport easily crystallized and solidified media. The insulated shell is filled with hot water, steam, and other thermal media to keep the ball valve insulated.

2.  Structure and characteristics of 2-PC ball valves

The valve body of a two-piece ball valve is composed of two parts: the main valve body and the auxiliary valve body. Therefore, it is called a two-piece ball valve. It is a commonly used ball valve. After the ball core, valve seat, and valve stem are installed in the main valve body. The auxiliary valve body is connected to the main valve body through threads or bolts. The ball core has a full diameter size, low flow resistance, and high flow capacity.

Two-piece ball valves also have internal threaded connections, external threaded connections, and internal and external threaded connections. The thread usually adopts 55 degrees taper pipe thread, which has good sealing performance. 2-PC flange connected ball valves are widely used.

3. Structure and characteristics of 3-PC ball valves

The valve body of a three-piece ball valve is composed of one main valve body and two auxiliary valve bodies, so it is called a three-piece ball valve. After the ball core and valve stem are installed in the main valve body. The auxiliary valve body is installed in the valve seat, and the main and auxiliary valve bodies are connected together through bolts. The ball core is also of full-bore size.

The 3-PC ball valve also has internal thread connection, external thread connection, and the internal thread usually adopts 55 degrees cone pipe thread, which has good sealing performance. It can be welded with pipelines. It is more convenient to disassemble and assemble during maintenance, avoiding the need for separate unions for internal threaded connections.

Butt welding and socket welding can also be extended nozzle welding to avoid high temperature damage to the valve seat sealing ring and valve stem packing during welding, reducing the installation difficulty.

The main feature of the 3-PC ball valve is that it can be maintained online and it is very convenient. Unscrew the valve body and remove a bolt through the main valve body. Turn the main valve body to replace the seat ring. The main valve body bolt can also be completely removed and the main valve body can be removed for maintenance. The secondary valve body is still on the line, avoiding the removal of the entire ball valve and greatly reducing the maintenance workload.

4.  Differences between 1-PC ball valves, 2-PC ball valves, and 3-PC ball valves

1. The valve body structure is different. The body of one-piece ball valves is an integral type. The body of two-piece ball valves is divided into two main and auxiliary valve bodies, and the body of three-piece ball valves is divided into one main valve body and two auxiliary valve bodies.

2. The size of the ball core flow channel is different. The one-piece ball valve adopts a reduced diameter flow channel, which has a certain impact on the flow capacity. Two-piece ball valves and three-piece ball valves adopt full bore channel sizes. Small flow resistance leads to greater circulation capacity. Two-piece ball valves and three-piece ball valves can be selected for flow requirements.

3. The installation and maintenance workload varies. Three-piece ball valves are more convenient to install and maintain than one-piece ball valves and two-piece ball valves. 

4. The procurement costs are different. Three-piece ball valves of the same specification have the highest cost, followed by two-piece ball valves, and one-piece ball valves have the lowest cost.