A high quality gate valve should have the following characteristics:
① Sealing performance
There are three sealing parts of the valve: the contact between the opening and closing parts and the sealing surface of the valve seat; Packing with the valve stem and stuffing box; The connection between the valve body and the valve cover. The leakage in the first place is called internal leakage, which is usually referred to as lax closing, which will affect the ability of the valve to cut off the medium. For cut-off valves, internal leakage is not allowed.
The latter two leaks are called external leaks, that is, the medium leaks from inside the valve to outside the valve. Leakage will cause material loss, pollute the environment, and cause accidents in serious cases. For flammable and explosive, toxic or radioactive media, leakage is not allowed, so the valve must have reliable sealing performance.
② Action sensitivity and reliability
Refers to the sensitivity of the valve 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, traps and other valves with specific functions, their functional sensitivity and reliability are very important technical performance indicators.
③ Opening and closing force and opening and closing moment
Opening and closing force and opening and closing moment refers to the force or moment that must be applied to open or close the valve. When closing the valve, it is necessary to form a certain specific pressure seal between the opening and closing parts and the head sealing surface, and at the same time to overcome the friction between the valve stem and the packing, the valve stem and the screw thread between the valve stem and the nut, the valve stem end support and other friction parts, so a certain closing force and closing torque must be applied, the valve in the opening and closing process, the required opening and closing force and opening and closing torque are changed. The larger value is at the last instant of closing or the first instant of opening. The valve should be designed and manufactured to reduce its closing force and closing torque.
④ Strength performance
The strength 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 stiffness to ensure long-term use without rupture or deformation.
⑤ The flow medium
After the medium flows through the valve, there will be a pressure loss (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. From the perspective of energy conservation, when designing and manufacturing valves, the resistance of the valve to the flowing medium should be reduced as much as possible.
⑥ Opening and closing speed
Opening and closing speed is expressed by the time required for the valve to complete an opening or closing action. Generally, there are no strict requirements for the opening and closing speed of the valve, but some working conditions have special requirements for the opening and closing speed, such as some requirements for rapid opening or closing, to prevent accidents, and some requirements for slow closing, to prevent water strikes, etc., which should be considered when selecting the valve type.
⑦ Service life
It indicates the durability of the valve, is an important performance indicator of the valve, and has great economic significance. It is usually expressed by the number of opening and closing times that can ensure the sealing requirements, and can also be expressed by the use time.
