reprint from BALL VALVE WIKI 1.AppearanceThe floating ball valve and the trunnion ball valve are easy to distinguish in appearance. If the valve body has a fixed shaft on the bottom, it must be the trunnion ball valve.If the ball valve body has a device for injecting grease,it is basically a trunnion ball valve.However, if there is no injecting device,can we say it must be a floating ball valve? This is incorrect, because small size such as 2 "150LB trunnion ball valves are usually not filled with injecting device either.2. Sealing surfaceAs the ball of the floating ball valve is floating, so under the pressure of the medium, the floating ball will move and against the downstream seat., so the seal of the floating ball valve belongs to the single-side seal.The ball of the trunnion ball valve cannot be moved, so the two sides of the trunnion ball valve both must be sealed.Since the sealing principle is different, the requirements of the two ball valves on the sealing surface material are different, especially the sealing surface of the floating ball valve must be able to bear the pressure caused by the floating ball.3. Working principleThe floating ball valve only has upper stem and the ball can have a slight displacement, so it is called floating ball valve.The trunnion ball valve ball has another stem at the bottom to fixed the position of the ball,so the ball can&#;t move.The sealing of the floating ball valve is realized by the pressure of the medium,when the ball valve is closed, the floating ball is pressed against the sealing surface under the action of pressure to realize sealing.When the trunnion ball valve is closed, the ball does not produce displacement, but the floating seats will move and press against the ball under the action of the media pressure to realize sealing.4. ApplicationThe floating ball valve is suitable for medium and low pressure and usually has a small diameter.The trunnion ball valve can be used in high pressure conditions and the size can be up to 60 inches.The trunnion ball valve is a kind of double-block-and-bleed(DDB) valve, while the floating ball valve only seal the downstream side.The trunnion ball valve can block both upstream and downstream media. And when the pressure in the middle cavity is greater than the seat spring force, the seat will be pushed open to release the pressure inside the chamber to ensure safety.5.CharacteristicsTo the floating ball valves,the trunnion ball valves are usually used longer,has smaller size and easier to operate.The trunnion ball valve also has the function of automatic release pressure, when the medium temperature in the valve rises and causes abnormal pressure rise, the trunnion ball valve can automatically release the pressure without a relief valve,This is very important to ensure the safety of industrial production.
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XHVAL GROUP VALVE CO., LTD. is located in Wenzhou City, China. established in , engaged in professional valve development, manufacture and sale of professional valve manufacturers, with two subsidiaries; and sub-brand (XHVAL).
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