There are four common types of plug valves, each of which has specific characteristics and advantages.

Lubricated plug valve

The lubrication plug valve uses lubricant to reduce frictions and make each port tightly sealed. Lubricants are basicly base oils that increase the viscosity of moving parts, such as amorphous or fumed silica, which are injected between the valve plug surface and the valve body seat under high pressure.

The manufacturer suggest to using a lubricant that matches the process fluid and resealing the valve after a certain number of cycles (or after each cycle in some applications).

Because of this maintenance requirement, lubrication valves are used in non-continuous operation applications. This type of valve is suitable for processes where light abrasive particles are suspended in the fluid, such as upstream applications, gas pipelines that require bypass valves, and purge valves as valve stations and kick valves.

This type of plug device generally has a metal valve seat.

Non-lubricating type plug valve

This valve is characterized by a tapered or conical disc as a wedge, and a sleeve of soft material is pressed on the cavity of the valve body (the sleeve can reduce the friction between the plug mechanism and the valve body).

When low maintenance is required, such as in the service of sulfur or hydrogen fluoride, or where the fluid may freeze and block the valve, non-lubricated valves are more popular than lubricated valves.

The disadvantage of non-lubricated valves is that because they use a non-metal seat, they are only suitable for specific applications in terms of temperature, pressure and type of fluid (chemical resistance).

The three main types of non-lubricated valves are: fully lined, elastomer sleeves, and lift plug valves.

Eccentric type plug valve

The design of the eccentric valve has the characteristics of a half plug, which is a key advantage for applications that require stronger seat force and minimal friction from open to closed positions.

Compared with the concentric design, the closing capacity of the eccentric valve is also improved.

Typical applications of this type of plug valve are dirty water, sewage, sludge and mud, air and other similar services that require strict closure.

Double expansion type (double valve block and bleed;DBB)

This is the most complicated plug valve design, because it is characterized by multiple components, which make the valve mechanically expand, so that it has a true double blocking and deflation function.

In applications that do not require double isolation, they are often used to prevent product contamination.

The expansion valve uses a mechanism that rotates between open and closed positions and protects the two seals from the flow path. During the rotation, the valve body and the sealing ring are not in contact. When the valve is closed, the slider will expand to the valve body seat to prevent wear or abrasion of the sealing ring.