According to structure and function, it can be divided into:
1. There are several types of pneumatic ball valves. The floating pneumatic ball valve is used as a sealing element. The ball is floating. It uses the pressure of the medium itself to push the ball to produce displacement of the moving distance, squeezing the elastic valve seat to achieve the sealing effect. This kind of floating pneumatic ball valve has a large resistance to opening, which is only applicable to pipelines and equipment with a diameter of DN 200 and a pressure of PN 100. If the diameter of the ball is too large, the valve body will be bent under the pressure of the medium and become invalid; if the pressure is too large, the compression elasticity of the pneumatic ball valve will cause permanent deformation by using the elastic valve seat, which may damage the seal and affect the service life of the pneumatic ball valve.
2. The fixed pneumatic ball valve is fixed by the upper and lower valve stems. The valve seat is equipped with a plate spring or cylindrical spiral spring. When equipped, the spring of the valve seat is compressed to produce a preload, so as to achieve the initial sealing of the valve. During use, the pressure pushes the valve seat to move onto the ball to achieve sealing. Since the ball does not move, it is called a fixed pneumatic ball valve. Because its sealing reliability is far greater than that of the floating pneumatic ball valve, this kind of fixation has a wider range of applications, which can be applied not only to low pressure small caliber, but also to high pressure large caliber. However, its structure is relatively more complex and its price cost is higher. When selecting it, you should choose it according to the actual needs.
3. Eccentric semi pneumatic ball valve This pneumatic ball valve adopts an eccentric structure. Its structural principle is similar to that of the multi-level three eccentric hard sealing butterfly valve. The valve seat and ball are not worn and have the sealing function of closing more tightly. The ball is only 1/4 of the spherical surface of an ordinary pneumatic ball valve. It is light in weight and relatively inexpensive. This kind of ball valve has a shearing effect and can be used in medium pipelines containing long fibers, No jamming will occur.
4. Thermal insulation pneumatic ball valve The flange of thermal insulation pneumatic ball valve is one to two specifications larger than the general flange pneumatic ball valve. It adopts an integral valve body and a side mounted ball valve design. A metal jacket, also known as jacketed pneumatic ball valve, is welded between the enlarged flanges outside the valve body. Jacket interfaces are installed on both sides of the valve body, which can inject steam or other superheated gases to prevent the medium from solidification or crystallization at normal temperature. Thermal insulation pneumatic ball valve is mainly used in pipelines and devices that are easy to crystallize and need thermal insulation in petroleum, chemical, metallurgical and pharmaceutical systems.
5. V-shaped pneumatic ball valve is a kind of regulating pneumatic ball valve. The flow passage hole of the ball valve is very different from the straight through hole of the ordinary pneumatic ball valve. The ball valve is V-shaped and usually adopts a fixed structure with two upper and lower stems
6. Fluorine lined pneumatic ball valve is commonly used in the pipeline of equipment with low temperature and strong corrosive medium. This pneumatic ball valve is lined with PFA or FEP and other corrosion-resistant engineering plastics at all parts of the flow channel in contact with the medium. It can replace expensive stainless steel, Hastelloy, Monel alloy and No. 20 alloy under the condition that the service temperature of fluororubber is not exceeded in the low-pressure pipeline, solving the transportation problem of strong corrosive media in petrochemical and chemical pipelines

Analysis on the application of tetrafluoro compensator and the stress criterion of compensator support
There are a large number of hot air pipes on the new dry process cement consumption line to maintain the normal operation of the entire consumption system. On these pipes, the reasonably arranged contraction joints play the role of absorbing the pipe shrinkage, ensuring the safety of equipment and foundation. Whether the contraction joint can play its due role depends on whether the type selection is reasonable, whether the maintenance is scientific, and whether the device meets the requirements.
1 Model selection
The selection of contraction joint is usually to select the location of the fixed pipe during the process design and pipeline layout in the preliminary design. With the help of the fixed point, the complex pipeline system is divided into simple, a certain number of single contraction pipe segments, and then the axial displacement, transverse displacement and angular displacement of these pipe segments are calculated. Then stop selecting the contraction joint according to the moving medium, pressure, temperature, displacement, vibration, external conditions of the project, etc. in the pipe.
The contraction joints selected by cement plants can be divided into metal bellows contraction joints and non-metallic flexible contraction joints.
The metal bellows shrink joint has high temperature resistance, long service life, and can accept high pressure and high negative pressure, but its price is high, so it can only absorb axial displacement. To absorb the lateral displacement, a straight section must be added between the two contraction joints (i.e. the small pull rod and the large pull rod in the contraction joint sample). The price of this kind of contraction joint is higher, and the space required in the pipeline is large. The rebound force of the metal contraction joint increases the load of the bearing, and the civil engineering cost of the tetrafluoroethylene compensator increases. Therefore, if the axial displacement is large, there is no transverse displacement or the transverse displacement is very small, and there is no vibration in the design, the device position of the contraction joint is at a place where it is inconvenient to change, we choose the metal bellows contraction joint. Such as air duct from cylinder c to humidification tower, kiln tail preheater, tertiary air duct, air duct from high-temperature fan to humidification tower, etc.
The non-metallic contraction joint can provide larger multi-dimensional compensation in a smaller size range. Since the main materials of non-metallic contraction joints are fiber fabrics and rubber, which have the characteristics of sound absorption, vibration isolation and transmission, powerless transmission, etc., they are often used on the inlet and outlet of boilers, fans, and mill exhaust hoods. Due to the powerless transmission, the use of non-metallic contraction joints can simplify the design, so we currently use a large number of non-metallic contraction joints in our design. However, with the increase of new dry process kiln waste heat power generation projects, the proportion of metal bellows shrink joints in cement plants will increase.
The contraction joint is used on the pipe system to absorb the thermal contraction difference, and also receives the pressure of the system. The operating temperature of the metal bellows contraction joint is between 180 and 1000 ℃; The pressure range is about - 1.75 × 10~~7 MPa. The process pipeline of the tetrafluoro compensator cement plant usually works under negative pressure.
The load-bearing support of the axial bellows compensator is divided into main fixed support, secondary fixed support and guide support.