What are the uses and characteristics of butterfly valves？

The closing member is a disc-shaped butterfly plate. The valve that rotates around a fixed axis in the valve body to open, close and regulate the fluid is called a butterfly valve. Butterfly valve is the fastest growing valve type in recent times. It has the characteristics of simple structure, small size, light weight, low material consumption, small installation size, rapid opening and closing, 90° reciprocating rotation, and small driving torque. It is used to cut off, connect and regulate the medium in the pipeline. It has good fluid control characteristics and closing and sealing performance. The streamlined design of the butterfly plate reduces fluid resistance and is an energy-saving product.

Metal-sealed butterfly valves have developed rapidly. With the application of high-temperature resistance, low-temperature resistance, strong corrosion resistance, and high-strength alloy materials in butterfly valves, metal-sealed butterfly valves have been widely used under high temperature, low temperature, strong erosion and other working conditions. And partially replace the stop valve and gate valve.

Butterfly valves can be used to cut off media and regulate flow. Mostly used for medium and low pressure and medium and large diameter valves. At present, the parameters of domestic butterfly valves are as follows: nominal pressure ≤ PN63; nominal size DN50 ~ 4800; operating temperature t ≤ 600°C.

The diameter of butterfly valve has reached more than DN10000. The sealing ring material is generally made of rubber or plastic, but the working temperature is low; if the sealing ring is made of metal or other high-temperature-resistant materials, it can be used at high temperatures.

Since the movement of the butterfly valve plate is wiping, most butterfly valves can be used in media with suspended solid particles. Depending on the strength of the seal, they can also be used in powdery and granular media. It should be noted that multi-layer metal hard Sealed butterfly valves are not suitable for this working condition because once particles enter the non-metallic interlayer, the sealing performance will be affected and even the sealing surface will be damaged. The structure length and overall height of the butterfly valve are small, and the opening and closing speed is fast. When it is fully opened, it has small fluid resistance. When it is opened to about 15°~70°, it can perform sensitive flow control. The structure of the butterfly valve The principle is most suitable for making large diameter valves.

Under the following working conditions, it is recommended to use butterfly valves:

① Requires throttling, adjustment and control of flow;

② Mud media and media containing solid particles;

③ Where the valve structure is required to be short in length;

④ Where fast opening and closing speed is required;

⑤ When the pressure difference is small.

Butterfly valves can be used when there are double-position adjustments, constricted channels, low noise, cavitation and vaporization, a small amount of leakage into the atmosphere, and abrasive media.

When throttling is adjusted under special working conditions or strict sealing is required, or when butterfly valves are used under severe wear and low temperature (cryogenic) conditions, a specially designed triple-eccentric or double-eccentric butterfly valve with a specially designed metal seal with an adjustment device is required. .

Most of the butterfly valves that appeared in the early years were sealed with natural rubber seats. Although they have excellent sealing performance, the applicable temperature and pressure are low, generally around 70°C and not greater than PN10. Later, the emergence of synthetic rubber and its application in butterfly valves increased the applicable temperature to about 120°C and the applicable pressure to PN16 accordingly. In particular, the corrosion resistance and wear resistance have been greatly improved, and it is still widely used in the water supply and drainage industry today. With the rapid development of the chemical industry, the emergence of fluoroplastics has further improved the performance of butterfly valves. The butterfly valve seat made of PTFE material has increased the applicable temperature of the butterfly valve to 180°C, the applicable pressure has also been greatly improved, and its ability to withstand Corrosion from strong acids, strong alkali and chemical solvents.

The use of metal sealing materials and triple eccentric structure design have revolutionized butterfly valves. In the past, the problem of high pressure resistance and high temperature resistance has always been the weak link of butterfly valves. The sealing seat material of the butterfly valve is basically made of natural rubber, synthetic rubber, fluoroplastics and other materials, so the temperature and pressure it can withstand are limited.

Due to the application of metal rigid sealing rings, metal expansion sealing rings, metal elastic sealing rings, multi-layer stainless steel and graphite composite rings in butterfly valves, coupled with the eccentric butterfly plate structure, its edges are spherical, tapered and other forms and are combined with the metal elastic ring. Together, they form a tight sealing pair, thereby increasing the applicable pressure of the butterfly valve to above PN63 and the applicable temperature up to 600°C. Its excellent performance has been widely used in steam, gas, hot air and corrosive media and other fields.

According to the structural form, butterfly valves can be divided into the following types: centerline sealing butterfly valve, single eccentric butterfly valve, double eccentric butterfly valve, triple eccentric butterfly valve.

① Compared with other valves of the same specification and pressure level, the butterfly valve has a short structural length, small size, light weight and simple structure.

② It opens and closes quickly and is easy to operate. It can be used as a valve to open and close quickly.

③ It has good flow adjustment function and closing sealing performance, long service life, and can be used as a regulating valve.

④ Suitable for large-diameter valves and widely used in large water supply and drainage pipelines.