In 30 years, the United States created the butterfly valve, and it was introduced to Japan in 50 years, and it was only adopted in Japan in 60 years, and it was only 70 years later that it was implemented in our country. At present, the general butterfly valve above DN300 mm in the whole country has replaced the gate valve. Compared with the gate valve, the butterfly valve has a short opening and closing time, the dominance is small, the installation space is small, and the weight is light. Take DN1000 as an example, the butterfly valve is about 2T, and the gate valve is about 3.5T, and the butterfly valve is easy to be combined with various driving arrangements, which is exquisite and reliable.
The deviation of the rubber-sealed butterfly valve is caused by squandering and coaxing. The improper coaxing will cause negative cavitation and cause the rubber seat to peel off and damage the environment. For this reason, metal-sealed butterfly valves are now being developed overseas, and the cavitation zone has been reduced. In recent years, my country has also developed metal-sealed butterfly valves. In recent years, Japan has also developed cavitation-resistant, low-vibration, and low-noise comb-shaped butterfly valves.
Generally, the lifespan of the general sealing seat is 15-20 years for stainless steel flange rubber and 80-90 years for metal in a deformed environment. However, if you choose to use it correctly, you must ask for it according to the working conditions.
The relationship between the opening of the butterfly valve and the flow rate is adjusted in a linear proportion. If it is used for pipe bundle flow, its flow characteristics are also closely related to the flow resistance of the piping. For example, if the two pipes are installed with the same valve diameter and mode, but the pipe loss coefficient is different, the valve flow divergence will also be very different.
If the valve is in the form of a large amount of profligacy, the back of the valve plate will produce negative cavitation, which has the outline of a waste valve, and it is generally coaxed outside 15°.
When the butterfly valve is in the middle opening, the closed shape formed by the valve body and the front end of the butterfly plate takes the valve shaft as the core, and the two sides form different shapes. The front end of the butterfly plate on one side moves along with the purpose of the water mark, and the other side is downstream with the water mark. Therefore, the valve body and the valve plate on one side form a nozzle-like closed mouth, and the other side has the same squander hole-shaped closed mouth. The nozzle side has a much faster flow rate than the squandering side, and negative pressure will be generated on the squandering side valve. The rubber seals will appear scattered.
Each of the butterfly valve and the butterfly rod has no self-locking ability. For the positioning of the butterfly plate, the stainless steel flange must be equipped with a worm gear slower on the valve rod. The adoption of a worm gear slower not only provides the self-locking ability of the butterfly plate, but also allows the butterfly plate to be carried in a random position, and can also improve the dominance of the valve.
The butterfly valve dominates the torque, and its value varies due to the different opening and closing objectives of the valve. The horizontal butterfly valve is a large-diameter valve. Due to the depth of the water, the torque generated by the difference between the valve shaft and the upper water head cannot be ignored. In addition, when arranging elbows on the inlet side of the valve, a bias flow is formed and the torque will increase. When the valve is at both ends of the opening, due to the influence of the water flow torque, the dominating mechanism must be self-locking.
The butterfly valve mechanism is complicated, formed by only a few complete machines, which saves raw material consumption; small size, light weight, installation size , small driving torque, dominates cumbersome, rapid speed, only tampering with 90 ° can be opened and closed quickly; moreover, At the same time, there are exquisite flow regulation compliance and closing and sealing characteristics. In the field of large and medium caliber, medium and low pressure, the stock financing butterfly valve is the dominant valve mode. When the butterfly valve is in the completely ** position, the thickness of the butterfly plate is the only resistance when the medium flows through the valve body, so the pressure drop generated by the valve is very small, so there is a better flow tube characteristic. The butterfly valve has two sealing types: elastic seal and metal seal. Elastic sealing valve, the sealing ring is generally embedded in the valve body or attached to the periphery of the butterfly plate.
Valves with metal seals generally have a longer life than valves with elastic seals, but it is difficult to achieve a complete seal. Metal seals can adapt to higher task temperatures, while elastic seals have deviations limited by temperature. If you ask the butterfly valve to be used as a flow tube bundle, the main thing is to accurately determine the size and model of the valve. The mechanism of butterfly valve is especially suitable for manufacturing large-diameter valves. Butterfly valves are not only widely used in general properties such as kerosene, gas, chemical industry, and water treatment, but also operate in the cooling water system of thermal power stations.
Rarely used butterfly valves include wafer butterfly valves and flange butterfly valves. Wafer type butterfly valve uses double-head bolts to connect the valve between two pipe flanges. Flange type butterfly valve has flanges on the valve. The two flanges of the valve are connected to the pipe flanges with bolts. The strength compliance of the valve refers to the ability of the valve to accept the pressure of the medium. The valve is a rigid product that accepts internal pressure, so it must have sufficient strength and rigidity to ensure long-lasting coaxing without splitting or deforming.
Following the operation of anti-corrosion decomposition of rubber and polytetrafluoroethylene, the butterfly valve has been able to advance and be comfortable under different working conditions. In the past ten years, metal-sealed butterfly valves have been rapidly obstructed. Following the operation of high-temperature, high-temperature, strong-corrosion, strong-erosion, and high-strength alloy materials in butterfly valves, metal-sealed butterfly valves have been exposed to high temperature, high temperature, and strong erosion Under the premise of other working conditions, it obtains widespread operation, and all replace the containment valve, gate valve and ball valve.
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