There are many ways to classify plug valves. In this article, we will introduce four main type of plug valves.

1. Lubricated Plug Valve

A lubricated plug valve functions with the help of a lubricant (a base oil and viscosity improver) which is injected between the plug and body seat facing to reduce the frictions between them. The lubricated plug valve must be resealed after a few cycles. Due to its high maintenance, this kind of valve are often used in applications requiring less operations. Considering its metal to metal seat, the lubricated plug valves are suitable for fluids with some abrasive particles or high temperature.

2. Non-Lubricated Plug Valve

This plug valve utilizes a tapered plug and presses a non-metal sleeve against the body cavity. The sleeve can reduce friction between the plug and body.  Non-lubricated plug valves are often used in applications where maintenance needs to be kept to a minimum. However, non-lubricated plug valves are limited by temperature and chemical compatibility due to its non-metal sleeve and seat.

The three main types of non-lubricated plug valves are:

Lift-type plug valve

Elastomer sleeved plug valve

Fully lined plug valve

3. Eccentric Plug Valve

Like eccentric butterfly valve, the eccentric plug valve uses a half plug which is beneficial for applications requiring a higher seating force with minimal friction during valve operation. The torque seated valves also feature improved shut off capabilities. Eccentric plug valves are used for a wide range of flow control and isolation applications like clean and dirty water, sewage, sludge and slurries, air, and etc.

4. Expanding Plug Valve

This expanding plug valve uses multiple components that allow the valve to mechanically expand and give it a true double block and bleed function in one valve. The plug valve uses a mechanism that rotates between the open and closed position and protects both seals from the flow path. During rotation there is no contact between body and seals, and slips expand onto the body seat when the valve is closed to avoid causing any wear or abrasion to the seals. They are often used to prevent product contamination in applications that do not require a double isolation.