The Advantages and Disadvantages of Floating Ball Valve
Why the ball valve is called floating ball valve? Because it has a floating ball. Except for the two sealing rings used for sealing, the ball is not supported by any other components and the ball seems to be in suspension.
What is the principle of floating ball valve? Because the floating ball is not restricted by any components, when the valve is closed, the medium presses on one end of valve(upstream), and the ball is displaced to the outlet of the valve ( On the sealing surface of the downstream).
The floating ball valve has many advantages , like small flow resistance, simple structure, good sealing performance, and being cost-effective for certain size and pressure. But it also has some disadvantages. The medium load on ball will be completely on the downstream sealing ring. At the same time, the gravity of ball itself will also be directly absorbed by the sealing ring. Therefore, for valve with too high pressure , or too big size, some problems will be caused.
1. When the valve diameter is the same, the higher the nominal pressure is, the greater the load of medium on ball is. When the nominal pressure of valve is the same, the larger the valve s, the greater the load of medium on ball is. Therefore, for valve of same diameter, when the nominal pressure is high enough,floating ball structure will be not suitable. For ball valve of same pressure, when the valve is too big size, it is also not applicable.
2. Because the gravity of ball itself will be directly on the seal ring, when the ball is too heavy, the weights will be severely uneven on different positions of seal ring, which will result in irregular deformation of seal ring, and thus affects its service. Therefore, when valve is large enough, no matter how low the pressure is, the floating ball shouldn't be used.
3. the torque of ball valve is mainly deccided by the friction between ball and its seal ring.
There is a concept in the mechanical foundation: the friction between two objects (M) = positive pressure (F) * friction coefficient (f)
The coefficient of friction (f) is determined by the nature of the material itself, the material is selected, and the coefficient of friction is constant.The positive pressure (F) is proportional to the load (F1) of the working medium that the ball is subjected to.
From above, we can learn that when the load (F1) of medium on ball is large, the friction between the ball and the sealing ring will be large, and the torque will also increase. Therefore, when valve diameter or nominal pressure is of the same, the high pressure or big size will greatly increase the torque of ball valve.
Pls refer to the following when choosing floating ball valve or trunnion mounted ball valve.
PN ≤ 2.5MPA (or 150lb), DN ≤ 200mm (or 8")
(DN≤200mm (or 8") is a defective product, preferably trunnion mounted ball valve)
PN=4.0MPA (or 300lb), DN≤150mm (or 6”)
DN ≤ 150mm (or 6") is a defective product, preferably trunnion mounted ball valve)
PN=10.0MPA (or 600lb), DN≤100mm (or 4”)
PN=16.0MPA (or 900lb), DN≤50mm (or 2”)
PN=25.0MPA (or 1500lb), DN≤40mm (or 1.5”)
PN=42.0MPA (or 2500lb), DN≤25mm (or 1”)
What is the principle of floating ball valve? Because the floating ball is not restricted by any components, when the valve is closed, the medium presses on one end of valve(upstream), and the ball is displaced to the outlet of the valve ( On the sealing surface of the downstream).
The floating ball valve has many advantages , like small flow resistance, simple structure, good sealing performance, and being cost-effective for certain size and pressure. But it also has some disadvantages. The medium load on ball will be completely on the downstream sealing ring. At the same time, the gravity of ball itself will also be directly absorbed by the sealing ring. Therefore, for valve with too high pressure , or too big size, some problems will be caused.
1. When the valve diameter is the same, the higher the nominal pressure is, the greater the load of medium on ball is. When the nominal pressure of valve is the same, the larger the valve s, the greater the load of medium on ball is. Therefore, for valve of same diameter, when the nominal pressure is high enough,floating ball structure will be not suitable. For ball valve of same pressure, when the valve is too big size, it is also not applicable.
2. Because the gravity of ball itself will be directly on the seal ring, when the ball is too heavy, the weights will be severely uneven on different positions of seal ring, which will result in irregular deformation of seal ring, and thus affects its service. Therefore, when valve is large enough, no matter how low the pressure is, the floating ball shouldn't be used.
3. the torque of ball valve is mainly deccided by the friction between ball and its seal ring.
There is a concept in the mechanical foundation: the friction between two objects (M) = positive pressure (F) * friction coefficient (f)
The coefficient of friction (f) is determined by the nature of the material itself, the material is selected, and the coefficient of friction is constant.The positive pressure (F) is proportional to the load (F1) of the working medium that the ball is subjected to.
From above, we can learn that when the load (F1) of medium on ball is large, the friction between the ball and the sealing ring will be large, and the torque will also increase. Therefore, when valve diameter or nominal pressure is of the same, the high pressure or big size will greatly increase the torque of ball valve.
Pls refer to the following when choosing floating ball valve or trunnion mounted ball valve.
PN ≤ 2.5MPA (or 150lb), DN ≤ 200mm (or 8")
(DN≤200mm (or 8") is a defective product, preferably trunnion mounted ball valve)
PN=4.0MPA (or 300lb), DN≤150mm (or 6”)
DN ≤ 150mm (or 6") is a defective product, preferably trunnion mounted ball valve)
PN=10.0MPA (or 600lb), DN≤100mm (or 4”)
PN=16.0MPA (or 900lb), DN≤50mm (or 2”)
PN=25.0MPA (or 1500lb), DN≤40mm (or 1.5”)
PN=42.0MPA (or 2500lb), DN≤25mm (or 1”)
