Gate valve has the following characteristics:
The flow resistance is small.
Because the internal medium channel of the valve is straight, the medium flows in a straight line and the flow resistance is small.
It saves effort when opening and closing.
This is compared with the stop valve, because no matter it is open or closed, the movement direction of the valve seat is parallel to the direction of medium flow.
Large height, long opening and closing time.
The valve seat has a large opening and closing stroke, and the valve seat is lowered through a screw.
Water hammer is not easy to form.
The reason is that the shutdown time is long.
The media can flow in any direction to the left for easy installation.
The valve channel is symmetrical on both sides.
The structural thickness (the distance between the two connecting rims of the shell) is small.
The sealing surface is prone to rust, affecting its service life.
When opening and closing, the two sealing surfaces of the valve seat and the nozzle rub and slide against each other. Under the action of the medium pressure, scratches and rust are easily formed, which affects the sealing power consumption and reduces the service life.
Gate valve material type:
The materials of gate valves mainly include the following:
Iron gate valve:
Mainly made of iron materials such as cast iron or carbon steel, cast gate valve is currently widely used and relatively affordable. Its advantages are relatively low price, high strength, corrosion resistance, good sealing, and suitable for some common occasions. But the disadvantage is that it is heavy and has poor corrosion resistance and cannot be used in special environments such as high temperature and high pressure.
Stainless steel gate valve:
Made of 304, 316 and other stainless steel materials, it has excellent corrosion resistance and good durability, and is suitable for special environments such as high temperature and high pressure, such as the chemical industry, acid and alkali media treatment, etc. However, the disadvantage is that the manufacturing cost is relatively high, and care must be taken to prevent the influence of external foreign matter during use.
Copper gate valve:
Mainly made of copper materials such as brass and bronze, it has good corrosion resistance and sealing performance and is commonly used in chemical, food and other industries.
Alloy steel gate valve:
Alloy gate valve is also a common material. In terms of portability, dimensional accuracy and surface quality, aluminum alloy materials are superior to cast iron and copper alloys, and they also have certain temperature resistance and corrosion resistance. The disadvantage is that its ability to withstand pressure is not as good as steel, so it is suitable for some low-pressure situations.
The material selection of gate valves should be determined based on specific environmental requirements. Different materials have different characteristics and applicable occasions, and they need to be selected according to the actual situation.
Application scope of gate valve:
Urban water supply and drainage:
As a control valve on water pipelines, gate valves are widely used in municipal water supply and drainage pipe networks to control water flow and regulate water pressure.
Chemical industry:
In chemical production, due to the strong corrosiveness of the medium, the valves have higher requirements for durability, sealing and anti-corrosion. Gate valves can use gate plates and valve seats of different materials according to the requirements of different media, and have better corrosion resistance.
Electricity:
On the fuel pipeline used in thermal power generation, gate valves can control the fuel flow to ensure the safety and stability of combustion.
Metallurgy:
In the metallurgical industry, gate valves are often used to control the flow and pressure of various media during the smelting process to ensure the quality and efficiency of production.
Things to note when using gate valves:
The sealing performance of the gate is very high. During use, it is necessary to avoid hitting the gate, causing gate deformation and affecting the sealing performance.
During installation, attention should be paid to the cutting and supporting of the pipeline to ensure the normal operation of the gate valve and avoid friction between the pipeline and the gate valve.
During use, the status of the gate valve should be checked regularly and maintenance should be done in a timely manner.
A good valve should have the following advantages:
Sealing performance
The sealing performance of the valve refers to the ability of each sealing part of the valve to prevent medium leakage. It is the most important technical performance index of the valve.
There are three sealing parts of the valve:
① The contact between the opening and closing parts and the two sealing surfaces of the valve seat;
② Where the packing meets the valve stem and stuffing box;
③ The connection between the valve body and the valve cover.
The first leakage is called internal leakage, which is commonly referred to as lax sealing. It will affect the valve’s ability to cut off the medium. For cut-off valves, internal leakage is not allowed.
The latter two leaks are called external leakage, that is, the medium leaks from inside the valve to outside the valve. 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.
Action sensitivity and reliability
Refers to the sensitivity of the valve to respond accordingly to changes in media parameters. For valves such as throttle valves, pressure reducing valves, and regulating valves used to adjust medium parameters, as well as valves with specific functions such as safety valves and traps, their functional sensitivity and reliability are very important technical performance indicators.
Opening and closing force and opening and closing torque
The opening and closing force and opening and closing torque refer to the force or torque that must be exerted to open or close the valve. When closing the valve, it is necessary to form a certain sealing ratio between the two sealing surfaces of the opening and closing parts and the hair seat. At the same time, it is necessary to overcome the pressure between the valve stem and the packing, the thread between the valve stem and the nut, the end support of the valve stem and the due to the friction of other friction parts, 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 maximum value is at the final instant of closing. Or the initial moment of opening. When designing and manufacturing valves, efforts should be made to reduce their closing force and closing torque.
Strength performance
The strength performance of the valve refers to the valve’s ability to withstand the pressure of the medium. Valves are mechanical products that withstand internal pressure, so they must have sufficient strength and rigidity to ensure long-term use without rupture or deformation.
Flow medium
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. 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.
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 are no strict requirements for the opening and closing speed of valves, but some working conditions have special requirements for the opening and closing speed. For example, some require rapid opening or closing to prevent accidents, and some require slow closing to prevent water hammer, etc. This should be considered when selecting the valve type.
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, or it can also be expressed by the use time.
