1. The sealing principle of Taike floating ball valve
The opening and closing part of Taike Floating Ball Valve is a sphere with a through hole commensurate with the pipe diameter in the middle. A sealing seat made of PTFE is placed on the inlet end and the outlet end, which are contained in a metal valve. In the body, when the through hole in the sphere overlaps with the pipeline channel, the valve is in an open state; when the through hole in the sphere is perpendicular to the pipeline channel, the valve is in a closed state. The valve turns from open to closed, or from closed to open, the ball turns 90°.
When the ball valve is in the closed state, the medium pressure at the inlet end acts on the ball, generating a force to push the ball, so that the ball tightly presses the sealing seat at the outlet end, and a contact stress is generated on the conical surface of the sealing seat to form a contact zone The force per unit area of the contact zone is called the working specific pressure q of the valve seal. When this specific pressure is greater than the specific pressure necessary for the seal, the valve obtains an effective seal. This kind of sealing method that does not rely on external force, is sealed by medium pressure, is called medium self-sealing.
It should be pointed out that traditional valves such as globe valves, gate valves, centerline butterfly valves, and plug valves rely on external force to act on the valve seat to obtain a reliable seal. The seal obtained by external force is called a forced seal. The forced sealing force applied externally is random and uncertain, which is not conducive to the long-term use of the valve. The sealing principle of Taike ball valve is the force acting on the sealing seat, which is produced by the pressure of the medium. This force is stable, can be controlled, and determined by design.
2. Taike floating ball valve structure characteristics
(1) In order to ensure that the sphere can produce a force of the medium when the sphere is in the closed state, the sphere must be close to the sealing seat when the valve is assembled in advance, and interference is required to produce a pre-tightening ratio pressure, this pre-tightening ratio pressure It is 0.1 times the working pressure and not less than 2MPa. The acquisition of this preload ratio is completely guaranteed by the geometric dimensions of the design. If the free height after the combination of the sphere and the inlet and outlet sealing seats is A; after the left and right valve bodies are combined, the inner cavity contains the sphere and the width of the sealing seat is B, then the necessary preload pressure is generated after assembly. If the profit is C, it must satisfy: AB=C. This C value must be guaranteed by the geometrical dimensions of the parts processed. It can be assumed that this interference C is difficult to determine and guarantee. The size of the interference value directly determines the sealing performance and operating torque of the valve.
(2) It should be particularly pointed out that the early domestic floating ball valve was difficult to control due to the interference value during assembly, and was often adjusted with gaskets. Many manufacturers even referred to this gasket as an adjusting gasket in the manual. In this way, there is a certain gap between the connecting planes of the main and auxiliary valve bodies during assembly. The existence of this certain gap will cause the bolts to loosen due to the medium pressure fluctuations and temperature fluctuations in use, as well as the external pipeline load, and cause the valve to be outside. leak.
(3) When the valve is in the closed state, the medium force at the inlet end acts on the sphere, which will cause a slight displacement of the geometric center of the sphere, which will be in close contact with the valve seat at the outlet end and increase the contact stress on the sealing band, thereby obtaining reliability. The seal; and the pre-tightening force of the valve seat at the inlet end in contact with the ball will be reduced, which will affect the sealing performance of the inlet seal seat. This kind of ball valve structure is a ball valve with a slight displacement in the geometric center of the sphere under working conditions, which is called a floating ball valve. The floating ball valve is sealed with a sealing seat at the outlet end, and it is uncertain whether the valve seat at the inlet end has a sealing function.
(4) Taike floating ball valve structure is bi-direction, that is, two medium flow directions can be sealed.
(5) The sealing seat where the spheres are connected is made of polymer materials. When the spheres rotate, static electricity may be generated. If there is no special structural design-anti-static design, static electricity may accumulate on the spheres.
(6) For a valve composed of two sealing seats, the valve cavity may accumulate medium. Some medium may increase abnormally due to changes in ambient temperature and operating conditions, causing damage to the pressure boundary of the valve. Attention should be paid.
Post time: Sep-06-2021