Regarding the sealing issues before and after the fixed ball valve
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Fixed ball valves are installed with a sealing valve seat, and the ball can have two configurations: one with a sealing valve seat at the front of the ball, and another with a sealing valve seat at the back of the ball. Could you talk about their advantages and disadvantages?
There are two designs for the valve seat of fixed ball valves: one is a single-seal self-drainage design, and the other is a double-seal design. These designs are based primarily on the piston effect. In the single-seal design, when the pressure in the valve chamber exceeds the spring preload and the upstream pressure, the valve seat can be pushed open to allow the pressure in the chamber to be released into the pipeline. This design is commonly used in chemical processing plants, as it helps prevent dangerous substances from spreading into the environment, thus avoiding fires and the spread of toxic materials. Having valve seats on both the upper and lower sides enables dual-direction sealing, with no requirement regarding the installation direction. In the double-seal design, the pressure in the chamber cannot be released into the pipeline; it must be discharged externally through a dedicated outlet provided on the valve body. This design is often used in long-distance pipelines. If the inlet valve seat is damaged, the downstream valve seat can still provide sealing, so the service life of this type of seal is longer than that of a single-seal design. You can refer to the catalogs of ball valve manufacturers, as they usually provide information on this topic. Recommended brands include KTM (Japan)