Introduction and classification of plug valves

A plug valve is a type of valve that uses a rotating plug to control the flow of a medium in a pipeline. The plug, which acts as the closing element, rotates around the centerline of the valve body to open or close the passage. These valves are commonly used for cutting off, distributing, and changing the direction of fluid flow. With a simple design and quick operation—requiring only a quarter-turn to open or close—they are convenient to use and offer low resistance to fluid flow. Despite their long history, they remain widely applied today, especially in low-pressure, small-diameter, and moderate-temperature environments.

The plug and the plug body are typically designed with a conical shape, featuring a taper ratio of 1:6 or 1:7, ensuring a tight fit. There are several types of plug valves, each with unique sealing mechanisms:

First, the adapter-type plug valve is commonly used in low-pressure pipelines. Its sealing performance depends entirely on the precision of the fit between the plug and the body, which is tightened using a nut. This type is generally suitable for pressures up to 0.6 MPa.

Second, the stuffing-type plug valve uses packing material to seal between the plug and the body. This provides good sealing performance and eliminates the need for the packing gland to extend outside the valve body, reducing the risk of leakage. These valves are often used in applications with pressures up to 1 MPa.

Third, the self-sealing plug valve relies on the pressure of the medium itself to create a tight seal. The plug has a small protrusion that is pushed upward by the incoming fluid, creating a secure closure. This type is commonly used for air or similar non-corrosive media.

Fourth, in recent years, oil-sealed plug valves have gained popularity. These valves use forced lubrication to create an oil film between the plug and the sealing surface, improving sealing performance and reducing wear. They are more efficient and durable, making them ideal for a wider range of industrial applications.

Overall, plug valves offer a reliable and cost-effective solution for various fluid control needs, especially in low-pressure systems. Their versatility and ease of operation continue to make them a popular choice in many industries.