The United States invented the
butterfly valve in the 1930s. In the 1950s, it was introduced to Japan. In the 1960s, it was widely used in Japan. The promotion of butterfly valves in China was in the 1970s. The main characteristics of butterfly valves are small operating torque, small installation space and light weight. Take DN1000 as an example, the butterfly valve is about 2T, and the gate valve is about 3.5T. What's more, the butterfly valve is easy to combine with a variety of driving devices. It has good durability and reliability.
The disadvantage of rubber sealed butterfly valves is that when throttling, improper use will produce cavitation, so that the rubber seat will be peeled or damaged and so on. Therefore, we need to correctly choose the butterfly valve according to the requirements of working conditions. The relationship between the opening and flow of butterfly valves is basically linear proportional change. If it is used to control the flow, the flow characteristics and pipe flow resistance are also closely related. If the valve diameter and form of two pipeline installations are all the same, while the pipeline loss coefficient is different, the valve flow will be very different.
If the valve is in a large throttling range state, the back of the valve plate is prone to cavitation. There is a possibility of damage to the valve. It is generally used outside 15°. The two sides will form a completely different state. The front end of the butterfly plate on one side moves downstream water direction, and the one on the other side moves countercurrent water direction. Therefore, one side of the valve body and valve plate form one opening as the nozzle, and the other side is similar to throttle aperture openings. The flow rate of nozzle side is quicker than that of the throttling velocities. There will be negative pressure below the throttle side valve, and the rubber seals will often fall off.
The operating torque of butterfly valves is different due to the opening, valve opening and closing direction of different values. The operating torque of horizontal butterfly valves produced by the water depth, valve shaft, water head can not be ignored, especially for the large caliber valve. In addition, when the elbow is installed on the valve inlet side, the deflection will be formed, and the torque will increase accordingly. When the valve is in the middle opening, the operating mechanism needs to be self-locked due to the water flow torque.
The valve industry chain is numerous in China, but we are not the valve power. Generally speaking, China has entered the ranks of the world's valve powers. However, from the quality of products, China still has a long gap from the valve power. The production concentration of the industry is low, and the valve research and development ability of the best products is low. The valve industry manufacturing technology level is low. The import and export trade deficit is expanding.
There are absolutely not so many valve enterprises that can really survive in the market. However, the valve industry of this high-speed shock will bring great opportunities. The shock results will make the market operation more rational. Valve localization of the road abnormal "bumpy". Basic parts have become a short board restricting the development of China's manufacturing industry to modernization.
During the 12th Five-Year Plan period, the government will continue to increase the localization of Chinese equipment parts and components. Here, we select several representative valve industries mentioned in the Implementation Plan to carry out feasibility analysis of import substitution. It can be seen from the analysis that the feasibility of valve import substitution in each sub-industry is very different, and the valve urgently needs more policy guidance and scientific research support.
The valve industry in the development of the national economy, as an important link to the equipment manufacturing industry, plays a very important role. Due to China's domestic valve manufacturing level and the international advanced level, there is still a certain gap. A lot of high parameters, high temperature and high pressure, high pound key valves have been relying on imports. For example, the European OMAL brand has been the main choice of the domestic valve application industry. In order to push the valve localization, the China State Council issued "several opinions about accelerating the development of the equipment manufacturing industry. The relevant state departments, according to the requirements of the countries of major equipment localization, have made a series of major deployments. They are all led by the National Development and Reform Commission (NDRC),
China machinery industry federation and China general machinery industry association deploy and formula the relevant field of major equipment valve localization plan, and they coordinate with the relevant departments many times. Now the valve localization in the domestic valve industry has formed a consensus. International standards for product design will be actively adopted. The foreign excellent design structure (including patented technology) will be absorbed. Product test and performance inspection will be done in strict accordance with international standards. We need to absorb the experience of foreign production process and attach importance to the research and application of new materials. It makes clear the technical parameters and working conditions of imported high parameter valve products is to speed up the process of localization to promote the valve products constantly updated fully realizing the way of localization of the valve.
With the quickening pace of valve industry restructuring, the future industry will be the competition of the quality safety of valve products and product brand. Products are for high technology, high parameter, strong corrosion resistance and high life direction. The level of product technology will be improved gradually to meet the domestic equipment only through constant technical innovation, developing new products and technical renovation. We will fully realize the localization of valves. China's valve manufacturing industry in the huge demand environment will show a better prospect of development.
