Generally speaking, the national standard flanged ball valve is not a double seal, but it can also be made into a double seal, that is, the national standard double sealed flanged ball valve.

The double-sealed national standard flanged ball valve is a structure in which a layer of sealing ring is added to the stuffing box in the dynamic sealing device to achieve the double-sealing effect, which can ensure that the ball valve does not leak externally for a long time, prolong the normal service cycle of the ball valve, reduce the number of maintenance, and improve the safety during use. After the sealing packing layer is worn, it will not cause leakage immediately, and it can also achieve good sealing in the working environment with special requirements, such as corrosive medium.

The double-sealed national standard flanged ball valve includes a valve body, a spherical valve seat arranged on the valve body, a spherical valve core, a valve stem and a dynamic sealing device. The dynamic sealing device includes a stuffing box and a packing set between the valve body and the valve stem. The gland, the stuffing box is tightly pressed with a sealing packing layer through the packing gland, and a sealing ring is arranged in parallel with the sealing packing layer in the stuffing box. The sealing ring is arranged on the side of the sealing packing layer close to the valve body.