Selection of titanium pipe fittings

In recent years, the standardized production of titanium pipe fittings has risen in China, which is also a revolution in the application of titanium pipeline. It greatly improves the service life of titanium pipeline and promotes the application of titanium. The following is a detailed analysis and comment on the development history of China's standard titanium pipe fittings, the working conditions of titanium pipe fittings and the titanium pipe fittings used in the past, and introduces the advanced elbow production technology -- elbow pushing process. The titanium elbow produced by this process can ensure uniform wall thickness. This paper introduces the birth and development of domestic titanium pipe fittings standard, and the production and standardization of titanium pipe fittings in China.

Pipeline corrosion is a very serious damage factor in the development of modern industry. According to relevant media reports, more than 10 million tons of steel is lost every year in China. Titanium pipeline transportation is flammable, explosive, toxic and corrosive media, there is a lot of insecurity, so the requirements of titanium pipe fittings are higher.

Because of its high strength, light weight, good heat transfer and corrosion resistance, titanium has been accepted in many chemical industry applications. These properties of titanium make it a relatively economic solution when encountering engineering problems related to chemical industry. Although compared with general performance materials, the feeding cost is higher, but the life cycle analysis shows that titanium pipeline can be used to solve the engineering problems related to chemical industry The production cost can be reduced by reducing maintenance, reducing downtime, improving product quality and improving pipeline life.

At present, titanium pipeline has been widely used in chemical industry, petroleum industry, fossil industry, vacuum salt making industry, pharmaceutical industry, ocean engineering industry and electric power industry. Due to its good corrosion resistance, titanium materials have been widely used in severe corrosive media, such as ion-exchange membrane caustic soda and propylene oxide project. There are also formic acid, acetic acid, and methane oxide projects are using titanium pipeline transport medium. Solve the problem of pipeline corrosion.

1. Comparison of production process of titanium pipe fittings

Titanium has been used in the chemical system of civil industry since 1970s. As a kind of corrosion-resistant structural material used in chemical plant, titanium has established its position. Moreover, as an ideal material for chemical pipeline conveying corrosive medium, the life of pipeline depends on the pipe fittings. More and more engineers and technicians pay attention to titanium pipe fittings, especially the standardization of titanium pipe fittings Important.

1. Working condition of titanium pipe fittings

First of all, we analyze the working condition of a titanium pipe fitting. Titanium pipe mainly transports corrosive dangerous medium. When the medium with corrosive medium passes through the titanium pipe fitting, the medium carries a certain pressure, and the bearing pressure of each part of various pipe fittings is different. This paper analyzes the three most commonly used pipe fittings (elbow, tee, reducer).

Elbow: elbow is one of the important pipe fittings in various pipe systems. It can not only change the flow direction of medium, but also improve the flexibility of pipeline. When the medium passes through the elbow, the medium with pressure directly rushes to the back of the elbow, and the medium flows along the back to the outlet. It can be seen that the back of the elbow bears greater pressure and severe erosion corrosion, indicating that the back load is greater than any part.

Tee: the working condition of the tee is similar to that of the tube elbow, and the concentrated passing through the tee is the intersection of the branch and the straight road of the straight tee. At this time, the bearing pressure and erosion corrosion are greater than those of other parts. The pressure relief flow state of the branch pipe is the main pipeline.

Reducer: the working condition of the reducer. When the medium passes through the reducer, the medium usually flows from the big end to the small end. As the cross-sectional area gradually decreases, the cone part of the reducer will generate pressurization phenomenon, and the inner surface of the cone will not only bear large pressure but also bear serious erosion corrosion.

The above analysis shows that titanium pipe fittings are very important parts in titanium pipes, which directly affect the life of titanium pipes.

Common production process of titanium pipe fittings

Multi weld titanium elbow

In the early stage of using Taiyuan pipeline in China, there was no domestic manufacturer to produce standard titanium pipe fittings, so people had to use welding seam (commonly known as "shrimp waist" type) titanium elbow, and its processing technology was complicated. Generally, the pipe is cut into multi section inclined opening and welded, or the sheet metal is formed into multi section leaf shaped expansion material, and then rolled and welded, which leads to a large amount of weld. Because of the discontinuity of the weld geometry, the stress concentration of the Great Wall is higher. Therefore, the working pressure and temperature of the pipe must be regulated by accord. The weld will greatly reduce the corrosivity, easy leakage and poor appearance. The inner surface is a folded surface, which increases the pipeline transmission resistance and the back weld receives serious erosion corrosion, thus reducing the service life.

Welding tee: the tee is made by drilling on the straight pipe and welding the branch pipe directly. Because the processing performance of titanium material is inferior to other materials, the processing of welding joint is also very difficult. What's more important is that right angle is produced at the weld joint, which seriously affects the medium flow and increases the transmission resistance of the pipeline; the curve welding of the intersecting line is difficult; and the erosion corrosion of the right angle part increases, which makes the right angle part early damaged.

Welded titanium elbow: in order to improve the defects of multi welded titanium elbow, the half piece welded titanium elbow is used. Compared with the multi seam "shrimp waist" type, the weld seam is relatively less, and the weld seam is not corroded from the face to the lip brush, but is scoured along the direction, which is better because of the corrosion.

Cast elbow

Although a seamless elbow appears, the wall thickness (at least 5 mm) does not match the wall thickness (2 ~ 4 mm) of the can, which indicates that the smooth finish is poor and the transmission resistance is increased. What's more important is that there is a big inside