The valve is a control component in the pipeline fluid conveying system. It is used to change the passage section and the flow direction of the medium. It has the functions of diversion, cut-off, adjustment, throttling, check, shunt or overflow and pressure relief. Valves used for fluid control, from relatively simple globe valves to various valves used in extremely complex automatic control systems, have a wide range of varieties and specifications. Valves for industrial pipelines. The valve can be used to control the flow of various types of fluids such as water, steam, oil, gas, mud, various corrosive media, liquid metals and radioactive fluids. From the ultra-low temperature of -269℃ to the high temperature of 1430℃. The valve control can adopt a variety of transmission methods, such as manual, electric, hydraulic, pneumatic, worm gear, electromagnetic, electromagnetic-hydraulic, electric-hydraulic, pneumatic-hydraulic, spur gear, bevel gear drive, etc. ; Under the action of pressure, temperature or other forms of sensing signals, it can act according to predetermined requirements, or simply open or close without relying on sensing signals. The valve is driven by * or automatic mechanism to make the opening and closing parts lift, Sliding, pendulum or rotary motion, thereby changing the size of its flow channel area to achieve its control function.
1. Strength performance The strength performance of the valve refers to the ability of the valve to withstand the pressure of the medium. The valve is a mechanical product that is subjected to internal pressure, so it must have sufficient strength and rigidity to ensure long-term use without rupture or deformation.
2. Sealing performance The sealing performance of the valve refers to the ability of each sealing part of the valve to prevent the leakage of the medium, which 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 parts and the two sealing surfaces of the valve seat; the matching place between the packing and the valve stem and the stuffing box; the connection between the valve body and the bonnet. The leakage in the former part is called internal leakage, which is commonly referred to as lax closure, which will affect the ability of the valve to cut off the medium. For shut-off valves, internal leakage is not allowed. The leakage in the latter two places is called external leakage, that is, the medium leaks from the inside of the valve to the outside of the valve. External leakage will cause material loss, pollute the environment, and even cause accidents in severe cases. For flammable, explosive, toxic or radioactive media, leakage is not allowed, so the valve must have reliable sealing performance.
3. Flow performance After the medium flows through the valve, there will be a pressure loss (that is, the pressure difference before and after 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 to overcome the resistance of the valve. Considering energy saving, when designing and manufacturing the valve, the resistance of the valve to the flowing medium should be reduced as much as possible.
4. Action performance
1. Action sensitivity
This refers to the sensitivity of the valve to respond to changes in medium parameters. For throttle valves, pressure reducing valves, regulating valves and other valves used to adjust medium parameters, as well as safety valves, steam traps and other valves with specific functions, their functional sensitivity and reliability are very important technical performance indicators.
2. Opening and closing force and opening and closing torque
Opening and closing force and opening and closing torque refer to the force or torque that must be exerted by the valve to open or close. When closing the valve, it is necessary to form a certain sealing pressure between the opening and closing parts and the two sealing surfaces of the hair seat. The friction force of other friction parts, so a certain closing force and closing torque must be applied. During the opening and closing process of the valve, the required opening and closing force and opening and closing torque change, and the larger value is at the final moment of closing. or the initial moment of opening. The valve should be designed and manufactured to reduce its closing force and closing moment.