What is a gasket? A valve gasket is usually used to prevent pressure, corrosion, and natural thermal expansion and contraction leakage between two objects in the pipeline. Almost all valves that require flange connections will use valve gaskets, but their specific usage location and importance vary depending on the valve type and design. Next, let us explain the position of the valve and the material of the gasket.

The main usage position of 01 gasket: the "flange interface" of flange connected valves. The most commonly used valves are gate valves, globe valves, butterfly valves (especially centerline and double eccentric flange butterfly valves), and check valves. In these valves, the gasket is not involved in regulating flow or sealing the flow channel inside the valve, but is installed between two flanges (i.e. the flange of the valve itself and the flange of the pipeline), tightened with bolts to generate sufficient compression force, forming a static seal to prevent medium leakage from the connection. Its function is to fill the small uneven gap between two metal flange surfaces, ensuring 100% sealing at the connection.

The application of 02 gasket at the "valve cover" of many valves. In order to facilitate internal maintenance (such as replacing the valve seat, valve disc, and cleaning debris), the valve body and valve cover are manufactured separately and then connected with bolts. This connection also requires a gasket to seal. The connection between the valve cover and valve body of gate valves and globe valves usually requires the use of gaskets or O-rings. The gasket at this position also serves as a static seal to prevent the medium from leaking from the inside of the valve body into the atmosphere.

Some valves use "special gaskets" as part of their core sealing components and are designed inside the valve. 

1. Seat gaskets of butterfly valves

The seat of a butterfly valve is actually a circular gasket that is pressed into the inner wall of the valve body or installed around the butterfly plate. When the butterfly plate is closed, it will compress the valve seat gasket, forming a dynamic seal (because the butterfly plate is rotating). The material is usually rubber (such as EPDM, NBR, Viton) or PTFE to adapt to different media and temperatures.

2. Seat gaskets of ball valves

The seat of a ball valve is also a form of gasket, usually made of materials such as PTFE (polytetrafluoroethylene), PEEK (polyetheretherketone), or reinforced plastic. It provides a seal between the sphere and the valve body, which is both a static seal (relative to the valve body) and a dynamic seal (relative to the rotating sphere). Which valves usually do not use gaskets?

Valve with butt welding connection: The valve body is directly welded to the pipeline without the need for flanges and gaskets. 

Valves with threaded connections: They are sealed with threads (using tape, sealant, etc.) and generally do not require gaskets. 

One piece valve: Some inexpensive ball valves or specialized valves have a one-piece valve body that cannot be disassembled, so there is no valve cover gasket. Valves using O-rings or metal wrap gaskets: In some high-pressure, high-temperature, or special medium conditions, more advanced sealing forms may be used to replace traditional non-metallic gaskets.

Summary: Is the valve gasket useful? The valve gasket is a universal and critical sealing component, widely used in pipeline connections of various flange valves, as well as in valve cover sealing of many valves. When selecting, it is necessary to choose the appropriate gasket material and form based on the type of valve, connection method, medium, temperature, and pressure.