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.
cheng648771790,
Not sure that you have really nailed it with that post. Lot of words, but kind of lacking in relevance and focus.
In a floating ball valve the ball is not attached to the valve body and the seat-seal activation depends on differential pressure shifting the ball into the downstream seat.
The ball in a trunnion ball valve is rigidly attached to the valve body and the seat-seal is activated by springs located below the two seating surfaces (one on each side of the ball). Whether a trunnion ball valve is suitable for double-block-and-bleed applications is dependent on company policies and (occasionally) on regulations (see faq378-1612).
In appearance, the trunnion ball valve will always have a body bleed, and a floating ball valve will never have a body bleed.
Other than answering your own question by reprint from another website, what exactly is the question or purpose of this post?
I would take issue with item 4, there is no such thing as a "kind of DBB". That's like being a "kind of" pregnant. Sealing direction and effectiveness depends on the number and type of seal. Just because it's a trunnion valve doesn't make it "kind of DBB".
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
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