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Construction characteristics of Floating ball valve

 

Floating ball valve main characteristic is the ball without support axis, clamped by two seats in a "floating" state. Floating ball valve is mainly used for cutting off, distributing and changing medium’s flow direction. The main construction characteristics of the floating ball valve are sealing design for seat, reliable back sealing stem, fire prevention and anti- -static function, automatic pressure release and locking device, etc.
1. Valve locking device
To prevent misoperation, the fully opened or closed position of valve can be locked up, especially when valve are mounted outdoors or when valves are not allowed to be opened or closed by technical process. To prevent misoperation by other persons, it seems very important to have valve position locked up. Thereby, lockhole locating ab is designed if requested by users to meet the technological requirements of users
2. Anti-flyout Structure of Valve Stem
When medium pass through the valve, the pressure in valve body may possibly push the stem out, or when the valve is in repair, if there is pressure in the cavity, the stem or medium seems to easily fly out upon disassembling the valve, which can cause injuries to human beings. To prevent these possibilities, a dummy club is placed at the lower part of the stem. In this way, even if there is fire, packing and thrust bearing are burnt or packing is damaged due to other causes, the pressure of medium in valve body will make the dummy club of valve stem in close contact with the upper seal face of valve body, thus to prevent medium leaking out from the damaged packing position
3. Anti-static Device
When operating the valve, the friction between the ball and the nonmetal seat, like PTFE or etc. will produce electrostatic charge that can be accumulated on the ball. To prevent static spark, an antistatic device is placed on the valve to derive the electric charge accumulated on the ball from the static channel between the ball and the stem, or between the stem and valve body
4. Fire Protection Structure
In case of fire, the nonmetal packing or seat (non-fireproof material) will be burnt, the considerable medium leakage may possibly cause fire spread. Here, the fire protection structure functions to prevent medium from mass leakage. As shown in the figure, once the seat is burnt, the ball will directly contact the metal face or valve body, thus to prevent medium leaking out from the burnt seat. The design of fire protection and antistatic structure shall conform to the requirements of AP1607, JB/T6899 and the second part of BS6755
5. Middle Flange Leak-tight Structure
The connection between valve body and the left body is sealed by gasket. To prevent seal leakage resulted from fire, high temperature or vibration etc., the valve body and the left body is designed metal-to-metal contacted, thus to form up a seal flange to ensure leak-tightness
6. Dependable Seating Structure
The two-way sealing structure embodying the years of our manufacturing experience in ball valves and the internationally advanced technology can release the pressure at valve seat and ensure reliable seal under high or low pressure and vacuum state. When the pressure of medium is low, the contact area between valve seat insert and ball is relatively small, thus providing high sealing load to ensure dependable seating seal. When the pressure of medium is high, the contact area between valve seat insert and ball is relatively large, so that the valve seat insert can endure the considerable medium thrust and cannot be damaged
Regarding ball valves of very low working pressure, in consideration that the pressure of medium cannot guarantee the dependable seal of valve seat, and that the pretightening force will decease after a long time of service, so we apply leaf spring loaded seating structure for valves working under low and ultralow pressure or under vacuum conditions, thus to ensure persistent and dependable seal
The seating structure of medium and high temperature ball valves adopts PPL for seal ring that can serve a temperature of 300℃. Ball valves with metal seal and high temperature resisting materials can be used to deal with even higher temperature. This structure takes the function of one-way seal
7. Self-relieving structure
In case of abnormal rise of pressure in the middle cavity of valve resulted from the medium left there suffered from changes of pipeline pressure or medium temperature, automatic pressure relief of valve seat can be effected under the pressure of the medium itself, thus to guarantee the safety of valve
8. Full and reduced bore
We have ball valves of full and reduced bore to meet users' different needs. Full-bore ball valves have the some inside diameter as that of pipeline, with the lowest fluid resistance for the convenience of cleaning the pipeline. While reduced-bore ball valves weighs only 70% of the full-bore ball valve with the some caliber, a saver of cost and price, and its fluid resistance coefficient is only 1 /7 of that of the globe valve with the same caliber, so that reduced-bore valves are widely used abroad
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