The largest users of valves are the petrochemical industry, the power sector, the metallurgical sector, the chemical industry and the urban construction sector. The petrochemical industry mainly uses API standard gate valves, globe valves and check valves; the power sector mainly uses high-temperature pressure gate valves and globe valves for power stations. Check valves and safety valves and low-pressure butterfly valves and gate valves for some water supply and drainage valves; stainless steel gate valves, globe valves, and check valves are mainly used in the chemical industry; low-pressure large-diameter butterfly valves, oxygen globe valves, and oxygen ball valves are mainly used in the metallurgical industry; urban construction departments Low-pressure valves are mainly used, such as large-diameter gate valves mainly used in urban water pipelines, mid-line butterfly valves mainly used in building construction, and metal-sealed butterfly valves mainly used in urban heating; flat gate valves and ball valves are mainly used in oil pipelines; stainless steel is mainly used in the pharmaceutical industry Ball valves; the food industry mainly uses stainless steel ball valves. Due to changes in user needs, the market trend of valve products will also change accordingly. The main development trends in the future are as follows:
1.With the transfer of oil development to inland and offshore oil fields, and the development of the power industry from thermal power below 300,000 kW to thermal power above 300,000 kW, hydropower and nuclear power, valve products should also be changed accordingly according to changes in equipment application areas. Performance and parameters;
2.Urban construction systems generally use a large number of low-pressure valves, and have developed to be environmentally friendly and energy-saving, that is, the low-pressure iron gate valves used in the past have gradually shifted to environmentally-friendly rubber plate valves, balance valves, metal-sealed butterfly valves, and center-line sealed butterfly valves. Oil and gas transmission projects are developing towards pipelines, which in turn require a large number of flat gate valves and ball valves;
3.The other side of energy development is energy saving, so from the aspect of energy conservation, it is necessary to develop steam traps, and develop towards subcritical and supercritical high parameters;
4. The construction of power stations is becoming large-scale, so large-diameter and high-pressure safety valves and pressure reducing valves are required, and quick opening and closing valves are also required;
5.In response to the needs of complete engineering, the supply of valves has developed from a single variety to multiple varieties and multiple specifications. The valve required for an engineering project is increasingly provided by a valve manufacturer.
The sealing performance of the valve refers to the ability of each sealing part of the valve to prevent the leakage of the medium. It is the most important technical performance index of the valve. There are three sealing parts of the valve: the contact between the opening and closing member and the two sealing surfaces of the valve seat; the packing and the valve The joint of the stem and the stuffing box; the connection between the valve body and the bonnet. The previous leak is called an internal leak, which is commonly referred to as tightness, and it will affect the valves ability to cut off the medium. In the category, internal leakage is not allowed. The last two leaks are called external leakage, that is, the medium leaks from the inside of the valve to the outside of the valve. The leakage will cause material loss, pollute the environment, and cause accidents in severe cases. For flammable Explosive, toxic or radioactive media, leakage is not allowed, so the valve must have reliable sealing performance.
After the medium flows through the valve, there will be a pressure loss (the pressure difference between the front and the back of the valve), that is, the valve has a certain resistance to the flow of the medium, and the medium will consume a certain amount of energy in order to overcome the resistance of the valve. Considering energy conservation, the design When manufacturing and manufacturing valves, the resistance of the valve to flowing media should be minimized.
Opening and closing force and opening and closing moment
Opening and closing force and opening and closing torque refer to the force or torque that must be applied to open or close the valve. When closing the valve, it is necessary to make a certain sealing specific pressure between the opening and closing member and the two sealing surfaces of the hair base, and at the same time overcome the valve The friction between the stem and the packing, between the stem of the valve and the thread of the nut, at the end of the valve stem and other friction parts, so a certain closing force and closing torque must be applied.In the process of opening and closing the valve, the required The opening and closing forces and opening and closing moments change, and their maximum values are at the final instant of closing or the initial instant of opening. When designing and manufacturing a valve, it is necessary to reduce its closing force and closing torque.
Opening and closing speed
The opening and closing speed is expressed by the time required for the valve to complete an opening or closing action. Generally, there is no strict requirement for the opening and closing speed of the valve, but some operating conditions have special requirements for the opening and closing speed. If required, open or close quickly To prevent accidents, some require slow closing to prevent water hammer, etc., which should be considered when selecting the valve type.
Motion sensitivity and reliability
This refers to the degree of sensitivity of the valve to the changes in the medium parameters. For throttles, pressure reducing valves, regulating valves and other valves used to adjust the medium parameters, and safety valves, traps and other valves with specific functions , Its functional sensitivity and reliability are very important technical performance indicators.
It indicates the durability of the valve, is an important performance indicator of the valve, and has great economic significance. It is usually expressed in terms of the number of openings and closings that can ensure the sealing requirements, and can also be expressed in terms of service time.