The open and close parts of the ball valve are balls with circular channels, rotating about the axis perpendicular to the channels, the ball rotates with the stem to achieve the open and close channels. The ball valve only needs to rotate 90 degrees the operation and the very small rotational torque can close tightly. According to the need of working conditions, the assembly of different drivers to form a variety of different control methods of the ball valve, such as electric ball valve, pneumatic ball valve, hydraulic ball valve and so on.
In the choice of ball valve, people often ask: what kind of ball valve do I need?
In this paper, ball valve selection is divided into four steps:
Step 1: identify the use
Ball valve according to the general structure can be divided into floating ball valve, fixed ball valve, elastic ball valve three categories. According to different sealing performance is divided into hard-sealed ball valve and soft-sealed ball valve.
Among them the soft sealing ball valve sealing performance is better, can achieve zero leakage, generally used with corrosive media in the normal temperature and atmospheric pressure pipeline;
The hard sealed ball valve can be used not only for normal temperature and normal pressure, but also for low temperature and low pressure and high temperature and high pressure pipeline.
Step 2: confirm the connection
The common ball valve according to the connection form is divided into six categories: threaded connection ball valve, flanged ball valve, welded ball valve, on the clip ball valve, clamp ball valve, card sleeve moving ball.
In thread connection, flange connection, welding end connection, the first two most commonly used. Threaded connection of the main valve is the nominal size of 50mm below the valve, if the size is too large, the connection of the installation and sealing is very difficult.
Flanged valves are easy to install and disassemble, but they are bulkier and more expensive than threaded valves, making them suitable for pipe connections of all sizes and pressures.
Clamp connection is the valve installed in two pieces of flanges in the middle, the valve body usually have positioning holes to facilitate installation and positioning, with bolts directly to the valve and the two pipe clip together, than the flange connection is more flexible.
Welded connections are more reliable than flanged connections under more demanding conditions. However, soldered valves are difficult to disassemble and re-install, so their use is limited to situations where they generally operate reliably over a long period of time, or where conditions are harsh and temperatures are high.
A clamp is a connecting device that connects grooved fittings, valves, and pipe fittings to act as a hoop between quick connections, usually two with gaskets, rubber, silicone, and Teflon. The utility model has the advantages of good performance, high sealing degree and simple installation
Card sleeve moving: small size, light weight, simple structure, easy to disassemble, can withstand high pressure (1000 kg/cm 2) , high temperature (650 ° C) and impact vibration. Can choose a variety of materials, suitable for anti-corrosion. The machining precision is not high, convenient for high-altitude installation.
Step 3: confirm the material
Select materials for valve housing, internals, and sealing surfaces, in addition to the physical (temperature, pressure) and chemical (corrosive) properties of the working medium, should also master the level of media cleanliness (solid particles) , in addition, but also reference to the relevant provisions of the state and use sector.
The correct and reasonable choice of valve material can obtain the most economical service life and the best performance of the valve. Valve body material selection should be combined with applicable scenarios.
Cast iron:
Cast iron ball valves are generally divided into gray iron ball valve and ductile iron ball valve:
(1) gray iron ball valve, the carbon content is high (2.7% ~ 4.0%) , the carbon mainly exists in the form of Flake graphite, the fracture is gray, referred to as gray iron. Low melting point (1145-1250 ° C) , small shrinkage during solidification, compression strength and hardness close to carbon steel, low cost and low price of gray iron ball valve, suitable for general requirements of the occasion is not high.
(2) spheroidal graphite cast iron ball valve, the gray cast iron is obtained after spheroidizing treatment, the precipitated graphite is spherical, referred to as ductile iron. It has higher strength, better toughness and plasticity than common gray cast iron and is suitable for hot oil.
Carbon Steel:
applicable to nominal pressure PN ≤32.0 mpa, temperature -30-425 ° C of water, steam, air, hydrogen, ammonia, nitrogen and petroleum products and other media.
Stainless steel:
Stainless steel commonly used for ball valve body have stainless steel 304,316,304L, 316L:
Both 304 and 316 ball valves are 18Cr-9Ni, typical of 18-8 Cr-Ni Austenitic stainless steel. 316 mainly reduces CR content and increases Ni content and MO2% ~ 3% . Thus its corrosion resistance than 304 strong, suitable for chemical, seawater and other environment, 316 than 304 in high temperature environment more corrosion resistance. So in the high temperature environment, engineers will generally choose 316 materials components.
2,316L ball valve is generally used for health-grade food factory, beverage factory, biological factory.
Copper:
Under the normal pressure (1.0 mpa) , the copper ball valve with water medium is generally suitable for the temperature below 200 ° C, the copper ball valve generally meets the working condition below 260 ° , which should be fully satisfied when used on water. The copper ball valve itself has a compact structure, the sealing is reliable, simple in structure and convenient in maintenance. The sealing surface and the sphere are often in the closed state, not easy to be eroded by the medium and easy to operate and maintain. It is suitable for the common working medium such as water, solvent, acid and natural gas, etc. , but also suitable for working conditions of poor media, such as oxygen, hydrogen peroxide, methane and ethylene, etc. , are widely used in various industries.
Plastics:
The plastic ball valve is suitable for the closure of the conveying process with corrosive medium, and can be selected according to the different material temperature of -14 ° C ~ 100 ° C or -40 ° C ~ 140 ° C. Flexible rotation, easy to use. Plastic ball valve integral ball valve leakage point less, high strength, connecting ball valve assembly and disassembly convenience.
Step 4: Identify Stress
The pressure level of the valve is not lower than the pipeline design pressure level, generally do not deliberately choose higher than the pipeline design pressure level of the valve. For example: pipeline design pressure 1.3 mpa, design temperature 90 degrees, then the valve design pressure is: 1.6 mpa, design temperature can be 200 degrees. There’s no need to go for 2.0 mpa or higher.
The final ball valve selection, to combine the above four factors to make a comprehensive judgment, you need the ball valve for what scenario? Does it have to be hot? How often do they tear it down? What is your ideal price?
See here, you have a certain understanding of ball valve selection? If you still feel very complex, perhaps your valve sales will help you solve all this!
When you select the type of ball valve, the next step can determine the ball valve drive way, electric ball valve, pneumatic ball valve, hydraulic ball valve and so on, subscribe to the DKV Blog, we will share in the Blog.
