The difference between floating ball valve and fixed ball valve
The difference between floating ball valve and fixed ball valve
The main Ball valve product names of China Ball valve Network include:Electric V-shape Ball Valve，Electric Vacuum Ball Valve，External Thread Ball Valve, Butt Welded Ball Valve，Manual Wafer Ball Valve With Feedback Signal，Flange Ammonia Ball Valve，Flange Copper Ball Valve，Flange Fluorine-lined Ball Valve，Forged Brass Ball Valve (Butterfly Handle Type)
The ball of a floating ball valve is floating and does not have a fixed shaft. Under the pressure of the medium, the ball can produce a certain displacement and be tightly pressed against the sealing ring at the outlet end, ensuring the sealing of the outlet end. It belongs to single-sided forced sealing. When designing, special attention should be paid to whether the sealing ring material can withstand the medium load of the sphere, because the load of the working medium borne by the sphere is all transmitted to the outlet sealing ring. Therefore, this floating ball structure is widely used in medium and low pressure ball valves. In addition, the design should also consider the large torque required for operating large-diameter ball valves
Manufacturing standards for floating ball valves:
Standard Project API American Standard Series GB National Standard Series
Design specifications API 6D, API 608 GB/T 12237
Pressure and temperature rating ASME B16.34 GB/T 9131
Structural Length ASME B16.10 GB/T 12221
Flange type and size ASME B 16.47 API 605 GB/T9113.1、JB/T79.1-1994
ASME B16.25 GB/T 12224 for welding ends
Inspection and Testing API 6D GB/T 12224
The ball of a fixed ball valve is fixed with a fixed shaft and does not move under pressure. Therefore, in the design, the two sealing rings should have sufficient pre tightening force to ensure sealing, which belongs to double-sided forced sealing. Usually, thrust or sliding bearings are installed on the upper and lower valve stems that are integrated with the ball. Compared with floating ball valves, the force generated by the fluid pressure in front of the valve in the pipeline on the ball is transmitted to the upper and lower bearings during operation, and the ball does not move. The valve seal is achieved by the spring and medium pressure pushing the valve seat, so the valve seat will not bear excessive pressure. Therefore, the fixed ball valve seat deformation is small, the operating torque is light, the sealing performance is reliable, and it is suitable for long-distance pipelines and general industrial pipelines. Its safety and resistance to harsh environments have been specially considered in its design, and it is suitable for various corrosive and non corrosive media. It has a long lifespan and is particularly suitable for high-pressure, large-diameter applications.
In order to reduce the operating torque of ball valves and increase the reliability of sealing, oil sealed ball valves have emerged in recent years. They inject special lubricating oil between the sealing surfaces to form an oil film, which enhances sealing performance and reduces operating torque, making them more suitable for high-pressure and large-diameter ball valves.
Manufacturing standards for fixed ball valves
Standard Project API American Standard Series GB National Standard Series
Design specifications API 6D, API 608 GB/T 12237
Pressure and temperature rating ASME B16.34 GB/T 9131
Structural Length ASME B16.10 GB/T 12221
Flange type and size ASME B 16.47 API 605 GB/T9113、JB/T79
ASME B16.25 GB/T 12224 for welding ends
Inspection and Testing API 6D GB/T 12224
Fixed ball valves also have the following characteristics:
Double blocking and discharge function fire safety structure sealing emergency grease injection rescue
Reliable stem seal
1. Reliable sealing performance: The PTFE single sex material sealing ring is embedded in the stainless steel valve seat, and the metal valve seat is equipped with a spring at the end to ensure sufficient pre tightening force of the sealing ring. When the sealing surface of the valve wears out during use, the valve continues to ensure good sealing performance under the action of the spring.
2. Effortless operation: The ball is supported by upper and lower bearings, reducing friction and eliminating excessive torque caused by the huge sealing load formed by the inlet pressure pushing the ball and the sealing seat.
3. Fireproof structure: In order to prevent the PTFE sealing ring from burning out due to flammability or fire, causing significant leakage and fueling the fire, fireproof sealing rings are installed on the sphere and valve seat. When the sealing ring burns out, the valve seat sealing ring is quickly pushed onto the sphere by the spring force, forming a metal to metal seal and achieving a certain degree of sealing effect. The fire resistance test meets the requirements of API6FA and API607 standards.
4. Sealing emergency grease injection rescue: Due to foreign objects or fire in the medium causing accidental failure of the valve seat seal, the grease injection valve provides a quick connection with the grease injection gun, making it convenient and quick to inject sealing grease into the valve seat sealing area to alleviate leakage.
5. Automatic pressure relief function: When the pressure of the stagnant medium in the valve chamber abnormally increases beyond the preload force of the spring, the valve seat will retract and detach from the ball, achieving the effect of automatic pressure relief. After pressure relief, the valve seat will automatically recover.
6. Drain pipeline: Drain holes are installed on both the upper and lower parts of the valve body to check if there is any leakage in the valve seat. During operation, when the valve is fully open or fully closed, the pressure in the middle chamber can be relieved and the packing can be directly replaced; Fixed ball valves are widely used for cutting off or circulating media in transportation pipelines such as food, medicine, petroleum, chemical, natural gas, steel, environmental protection, and papermaking, as they can discharge trapped substances in the middle chamber and reduce the pollution of the medium on the valve. Corresponding cleaning agents or lubricants can also be injected into this device to clean the sealing surface.
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