However, it is found that the elastoplastic deformation ability and stability of PTFE under temperature change are still not very ideal, and there is a large cold flow trend; At the same time, since the operating pressure of pneumatic ball valve varies widely, the lip seal seat made of polytetrafluoroethylene as the sealing material is still prone to leakage under low pressure conditions or in long-term use. The way to solve this problem is to use a combined seal seat composed of an elastic expansion ring and a PTFE lip seal seat. It can rely on the good elastic-plastic deformation ability of the metal elastic expansion ring, enhance its overall elastic-plastic deformation ability and compensation ability, and improve the sealing ability of the pneumatic ball valve.

Installation matters of pneumatic butterfly valve: 1. Install the pneumatic butterfly valve at the correct position, otherwise it will break quickly and reduce the service life. 2. The hose can be installed horizontally, vertically or diagonally. The most ideal state is to install vertically. At the same time, the device should be prevented from being near the left side of the wheel. If necessary, a baffle can be installed. 3. Generally, pneumatic butterfly valves can be divided into three lengths: the first is the tightening length, that is, the length when the hose is tightened to the limit position; The second is the length of the device, which is the length of the hose when it is in the middle of half of the maximum displacement; The third is the stretching length, which is the length when the hose is stretched to the maximum limit. 4. When the hose is installed, the hose should be in the middle position. When the hose is installed at this position, it can move in two directions when it is subjected to axial load. Otherwise, if the hose can only move in one direction, the strength of the pneumatic butterfly valve will be affected and the service life will be reduced. 5. In the process of implementing the device, considering that using a ruler to measure the length of the hose according to the calculation results and then stopping the device may affect the consumption efficiency, some foreign consumers directly install the ruler on the hose and cut off the ruler after installation.
What is the reason why metal bellows are not used for bridges? The application range of metal bellows is getting better and better, but why not use metal bellows for bridges? Next, I will introduce the reasons why metal bellows are not used for bridges. 1、 The vertical size of the teeth of the flat metal corrugated pipe is small, so it is difficult to thread multiple prestressed steel strands. 2、 The gap between the flat metal bellows and the prestressed reinforcement is very small after the prestressed reinforcement passes through the reinforcement, so it is difficult to grout. 3、 Flat anchors and metal corrugated pipe flat pipes have wide plane dimensions, which has certain adverse effects on the pouring of concrete and the compactness of the bottom. 4、 The roundabout flexibility of the flat metal bellows is much worse than that of the circular bellows, which makes it difficult for the prestressed beam with complex reinforcement.
It is well known that the basic conditions for stress corrosion cracking of stainless steel are sensitive alloys (data elements), specific media (environmental elements), such as the use of austenitic stainless steel in chloride containing solutions; Certain tensile stress (mechanics,... elements), including external stress, phase transformation stress and residual stress. If these three basic conditions are met, stress corrosion damage of stainless steel may occur. When stress corrosion cracking occurs, there is no obvious average corrosion, so that there are few corrosion products, and sometimes it is difficult to find with the naked eye, so stress corrosion is a very risky destruction. The stress corrosion process can generally be divided into three stages: the first stage is the incubation period. In this stage, due to the partial corrosion process and the result of tensile stress, the cracks nucleate, that is, the corrosion sensitive parts of stainless steel preferentially form small pits; The second stage is the development period of corrosion crack. When the crack nucleates, under the combined action of tensile stress in the corrosion medium and metal, the crack expands, causing damage to the parts and generating elongated cracks; In the third stage, due to the partial concentration of tensile stress, the cracks grow rapidly and expand rapidly, which can cause serious damage in a short time.
Elements of stainless steel ripple affecting stress corrosion: the stress corrosion cracking of stainless steel is related to the characteristics of the medium, temperature and stress, as well as the composition and structure of the steel. The impact of these elements is introduced below. 1 Effect of chloride ion concentration Generally speaking, the time required for stress corrosion cracking of Cr Ni stainless steel decreases with the increase of chloride concentration. It is generally believed that MgCl2 is most likely to cause stress corrosion cracking, and the corrosion effect of different chlorides is in the order of Mg2+, Fe3+, Ca2+, Na+, Li+plasma. 2. Influence of medium temperature: It is generally believed that stress corrosion is easy to occur when the temperature rises, but the temperature transition is too high, and stress corrosion is controlled due to overall corrosion. Some steels also have a critical fracture temperature. According to statistics, the temperature range of stress corrosion of Cr Ni austenitic stainless steel is between 50 ℃ and 300 ℃. 3 Effect of alloy elements and stress: It can be seen that the increase of alloy elements nickel and silicon in steel can improve the stress corrosion cracking resistance of austenitic stainless steel in MgCl2 solution, while nitrogen, phosphorus and other elements in steel can reduce the stress corrosion cracking resistance of stainless steel in concentrated chloride medium.