The Design and Development of Fixed Titanium Ball Valves
Titanium has good mechanical properties and excellent corrosion resistance. Therefore, it is widely used in the chemical industry, medicine and health, salt, Chlor-alkali, aviation and other areas. In the chemical industry, it is mainly used as the pressure vessel, pipeline and pump valve. Iron fixed ball valves have good sealing and excellent corrosion resistance. It can adapt to high working pressure. Therefore, it is widely used in the petroleum and chemical industries.
At present, there is no fixed titanium ball valve. There is only the floating type titanium ball valve. In the world, there are only a few countries such as the United States, Germany, and Japan, which can produce the titanium fixed ball valve. In order to satisfy the petrochemical industries’ needs for using it with high working pressure, good sealing, and good corrosion resistance, the use scope of titanium is broadened, and the design and development of titanium fixed ball valves are conducted. DN80, DN50, DN40, and DN25 fixed titanium ball valves were developed, and the use pressure can reach as high as 9.8MPa. It fills the gap in the domestic, lays a foundation for mass production and provides a technical and material guarantee for the domestic transformation of corrosion resistance equipment for large petrochemical enterprises.
This article describes the design, calculation process, main development technology and characteristics of fixed titanium ball valves.
1. Design and Development
1.1 Design Calculation
1.1.1 Design Technical Parameters
Working medium: acetic acid
Service temperature: 225℃
Design pressure: 9.8MPa
Nominal diameter: 80mm
1.1.2 Material selection
According to the use of temperature and concentration of acetic acid, it is found that the corrosion rate of titanium is less than 0.127mm/a. Compared with corrosion-resistant stainless steel and other non-ferrous metals, the TA2 is suitable for use. According to the working pressure, we should choose TA2 forging parts in order to ensure their structural strength. According to the use of temperature and working pressure, we should choose flexible graphite and antimony graphite as sealing materials.
1.1.3 Design Calculation
(1) Design of the wall thickness of the valve body
The formula: SB=DN(K0-1)/s+C
The calculation result is 16mm.
(2) Selection of connecting bolt between the valve cover and valve body
According to the working pressure, 1Cr18Ni9Ti bolts are selected, and 8 bolts of M30mm×55mm are selected to meet the strength requirements.
According to the formula, the connection bolts between the inlet and outlet flange cover and the valve body are 8 M30mm×45mm 1Cr18Ni9Ti bolts, which can meet the strength requirements.
1.2 Key Technologies
Since the working pressure is up to 9.8MPa, sealing and bearing pressure are the key technology. In the development process, three measures are adopted to solve this key technical problem.
(1) Ensure the coaxiality between the ball body and up and down the cue.
(2) Ensure the vertical degree between the upper and lower cue and Φ80mm through the hole.
(3) Ensure the roughness of the sphere.
The sealing and pressure-bearing targets have been achieved through the design of special tooling and sealing technology.
1.3 Structural features
Titanium fixed ball valves have the following three characteristics compared with floating ball valves.
(1) In the principle of sealing, rear sealing is adopted.
(2) It is suitable for high-pressure and viscous liquids.
The ordinary floating titanium ball valve is not reliable at high pressure. When the medium is the viscous liquid, the ball and the small floating gap between the sealing ring is easy to cause blockage. Therefore, the opening and closing of the valve are difficult or the sealing effect loses. The fixed titanium ball valve can achieve a good sealing effect by the use of a high-pressure medium as the use of the spring makes the sealing ring and the ball always maintain close contact.
(3) Wire sealing
The sphere and sealing ring of the ordinary floating titanium ball valve is sealed with spherical surfaces. The sealing-specific pressure on the unit area is small. In addition, the convex and concave points on the micro surface are easy to cause leakage under high pressure, which cannot meet the sealing requirements. The fixed titanium ball valve adopts line sealing between the ball and the sealing ring, which increases the specific sealing pressure per unit area. The higher the pressure, the better the sealing effect. Therefore, it can ensure the reliability of high-pressure work.
2. The conclusion
(1) The designed and developed fixed high-pressure titanium ball valve meets the needs of the petrochemical industry and it is in good use.
(2) The fixed high-pressure titanium ball valve has the characteristics of reliable high-pressure use and good sealing.
(3) The design and development of fixed high-pressure titanium ball valves is a domestic leader at the technical level and reached the international level of similar products.
