What kind of sealing conditions should be selected when the flow medium of the pneumatic ball valve

The sealing form of pneumatic ball valve can be divided into the form of soft seal and hard seal, the sealing of soft seal is good but not resistant to high temperature, and the hard seal can withstand high temperature but the sealing is not stable enough, generally speaking, the medium of about 300 is recommended to be hard seal, like the material of soft seal can only be about 160, I am now using the butterfly valve of Wicknd, and 400 is using a hard seal, so you should choose a hard seal with high temperature resistance for 300.

Gibbs free energy g=h+ts, Helmholtz free energy a=u+ts, then the difference between the two g-a=h-u, and h=u+pv, so g-a=pv ideal gas equation of state pv=nrt=2*

So g-a=pv=

The sealing conditions must be dry and ventilated.

The pneumatic ball valve only needs to be operated by a pneumatic actuator with a 90-degree rotation of the air source and a small torque to close tightly. The completely equal body cavity provides a straight-through flow path with minimal resistance to the medium. It is generally considered that ball valves are most suitable for direct opening and closing.

The main feature of the ball valve is that it is compact in its own structure, easy to operate and maintain, and is suitable for general working media such as water, solvents, acids and natural gas, but also for media with harsh working conditions, such as oxygen, hydrogen peroxide, methane and ethylene. The ball valve body can be monolithic or combined.

The flow medium is 300 belongs to the high-temperature medium, so it is best to choose a hard seal when choosing, such as pneumatic stainless steel ball valve and pneumatic hard seal butterfly valve, which one to choose should be decided according to their own working conditions and budget, generally pneumatic stainless steel ball valve will be more expensive than pneumatic hard seal butterfly valve, especially like Oumar, Wicken this kind of manufacturers, the difference will be greater!

The medium is gas (air), and the air valve should be selected.

Valves are control components in fluid transportation systems, which have the functions of shut-off, regulation, diversion, prevention of backflow, pressure stabilization, diversion or overflow pressure relief.

Valves for fluid control systems range from the simplest shut-off valves to the most complex valves used in automated control systems. Valves can be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, slurries, oils, liquid metals and radioactive media. According to the material, the valve is also divided into cast iron valve, cast steel valve, stainless steel valve, chromium-molybdenum steel valve, chromium-molybdenum vanadium steel valve, duplex steel valve, plastic valve, non-standard customized and other valve materials.

Valve is a device used to control the direction, pressure, and flow of fluid in a fluid system, and is a device that makes the medium (liquid, gas, powder) in the piping and equipment flow or stops and can control its flow.

The valve is a control component in the pipeline fluid transportation system, which is used to change the channel section and the direction of medium flow, and has the functions of diversion, cut-off, throttling, check, diversion or overflow pressure relief. Valves for fluid control, from the simplest globe valves to the most complex automatic control systems used in a variety of valves, its varieties and specifications, valves from the very small instrument valve to the diameter of 10m for industrial pipelines. It can be used to control the flow of various types of fluids such as water, steam, oil, gas, mud, various corrosive media, liquid metal and radioactive fluids, the working pressure of the valve can be from 1000MPa to ultra-high pressure, and the working temperature can be from C-270 ultra-low temperature to 1430 high temperature.

Classification by role and use.

1) Cut-off valves: such as gate valves, globe valves, plug valves, ball valves, butterfly valves, needle valves, diaphragm valves, etc.

Cut-off valves, also known as closed-circuit valves and globe valves, are used to connect or cut off the medium in the pipeline.

Check valve, also known as check valve or check valve, check valve is an automatic valve, its function is to prevent the reverse flow of the medium in the pipeline, to prevent the pump and drive motor from reversing, and the leakage of container medium. The foot valve of the suction off of the water pump also belongs to the category of check valves.

Explosion-proof valves, accident valves, etc., the function of safety valves is to prevent the medium pressure in the pipeline or device from exceeding the specified value, so as to achieve the purpose of safety protection.

Regulating valves, throttle valves and pressure reducing valves, their functions are to regulate the pressure, flow and other parameters of the medium.

2) Vacuum: such as vacuum ball valves, vacuum baffle valves, vacuum inflation valves, pneumatic vacuum valves, etc. Its function is in the vacuum system, the vacuum system element used to change the direction of the air flow, adjust the air flow volume, cut off or connect the pipeline is called the vacuum valve.

3) Special purpose: such as pig valve, vent valve, sewage valve, exhaust valve, filter, etc.

Exhaust valve is an indispensable auxiliary component in the pipeline system, which is widely used in boilers, air conditioners, oil and gas, water supply and drainage pipelines. It is often installed at the commanding height or elbow to remove excess gas in the pipeline, improve the efficiency of pipeline use and reduce energy consumption.

Ball valves may be the best choice in this case, or gate valves if they are dust-free.

Ball valves can be used for air, but they are slightly more expensive, and butterfly valves can also be used for slightly cheaper.

High temperature is a medium that is destructive to soft sealing materials.

The temperature is more than 200 degrees Celsius or there are particles in the medium.

Because the surface of the ball is treated with special surface hardening, and the valve seat is made of hardfacing cemented carbide, it can withstand the erosion of the medium well in the opening and closing process of the valve, and is especially suitable for solid particles and abrasive media.

The hard seal ball valve adopts an elastic loading structure, which ensures the contact between the ball sealing surface and the valve seat seal under normal closing conditions, and can effectively compensate for the thermal expansion of the internal parts under high temperature conditions, avoiding jamming caused by high temperature, and is suitable for medium and high temperature use occasions.

In addition to the special surface treatment of the ball surface and the valve seat surface, flexible graphite and metal winding gasket are used in other sealing materials, so they can be used for high temperature and high pressure working conditions, and have the function of fire resistance.

Compared with other valve types, pneumatic ball valves have quarter-turn output torque, fast opening, smooth and reliable, and are widely used, as well as some of the following advantages.

Anti-static function: A spring is set between the ball, the valve stem and the valve body to export the static electricity generated during the switching process.

Long service life: Because PTFE and other materials have good self-lubrication, the friction loss with the ball is small, so the pneumatic ball valve.

Low fluid resistance: Pneumatic ball valves are the least fluid resistance of all valve classifications, and even reduced pneumatic ball valves have quite little fluid resistance.

Reliable stem sealing: it has two sealing surfaces, and the sealing surface material of the ball valve is widely used in various plastics, with good sealing and complete sealing. It has also been widely used in vacuum systems.

Because the valve stem only rotates and does not lift and fall, the packing seal of the valve stem is not easy to break, and the sealing capacity increases with the increase of the pressure of the medium.

Good seat sealing performance: the sealing ring made of elastic materials such as PTFE is used to seal the structure is easy to seal, and the sealing capacity of the pneumatic ball valve increases with the increase of medium pressure.

Thrust bearings reduce the friction torque of the stem, which can make the stem operate smoothly and flexibly for a long time.

Simple structure, small size and light weight.

Easy to operate, quick to open and close: from full open to full closed, only 90° rotation is required, which is convenient for long-distance control.

Easy maintenance: The structure of the ball valve is simple, the sealing ring is generally movable, and it is more convenient to disassemble and replace.

When fully open or fully closed, the sealing surface of the ball and the valve seat is isolated from the medium, and when the medium passes, it will not cause erosion of the sealing surface of the valve.

Wide range of applications: diameters from a few millimeters to several meters, from high vacuum to high pressure. Since the ball valve is wipeable during opening and closing, it can be used in media with suspended solids.

High processing accuracy: expensive cost, not suitable for use in high temperature, such as impurities in the pipeline, easy to be blocked by impurities, resulting in the valve can not be opened.