1.Appearance
The 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 surface
As 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 principle
The 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. Application
The 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.Characteristics
To 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.
Floating ball spheres is floating in medium pressure function, ball of displacement and physical produce certain tightly compressed the seal surface in exports, ensure outlet seal.
Floating ball valve small volume, light weight, simple structure, good sealing, but ball work under medium load all passed to export sealing ring .So we must consider sealing materials can withstand the work load. Ball media This structure, widely used in low-pressure valve.
Floating ball valve features and performance
Small volume, light weight, simple in structure and function, with freely floating ball can better guarantee seal; Ball valve with circular hole sphere as on-off pieces, in stem drive next ball around stem centre for 0 ~ 90 degree rotated, complete opening and closing functions; With compact structure, turning the characteristics of quick opening 90 degrees, can close the valve, cut pipeline medium; Sphere passage diameter and pipe diameter, the same small flow resistance, circulation ability; Stem to remove theatrical makeup and costume type, to eliminate the stem wear out the accident happened, to ensure the safe use of;
Trunnion ball valve sphere is fixed, do not produce mobile after pressurized. Trunnion ball valve with floating seat. After medium pressure, seat produce mobile, make seal tightly compressed in ball, to ensure that the seal. Usually in the upper and lower with ball bearing, operation with shaft torque is small, be applicable to the high pressure and large diameter valve.
Trunnion ball valve suitable for various in high pressure piping, used in the medium truncated or connect piping, choose different material, which applies to water, steam, oil products, liquefied petroleum gas, natural gas, coal gas, nitric acid, acetic acid, oxidizing medium, urea and so on widely used in petroleum chemical power water conservancy and other industries. Trunnion ball valve common driving way for worm gear, manual and electric and pneumatic. Most trunnion ball valve are flange connection, but also have welding form of trunnion ball valve.
