Here are the fire protection design of double eccentric soft seal butterfly valves.
The structure of the
butterfly valve is very simple. It has a small size, light weight, simple design, and simple operation. The structure principle is suitable for the production of large-diameter valves. It can better limit the flow, so it is widely used in petrochemical, metallurgical steel, water treatment, power and other industries.
In recent years, with the continuous development of industrial technology, the butterfly valve has become one of the fastest developing
valve types. Its application is wider and wider. The design type and number are also expanding. It develops towards high-temperature resistance, high pressure, strong sealing, long service life and other multi-functional directions.
The double eccentric butterfly valve is also known as the high-performance butterfly valve. It is especially used in water plants, power plants, steel smelting, the chemical industry, water source engineering, environmental facilities and other systems like drainage. The water pipeline has a key role, in regulating and intercepting equipment. With the development of technology and the change of people's needs, the structure of butterfly valves has overcome real shortcomings and got continuous improvement. It has a great market prospect now.
Overview of the butterfly valve
From the design of the butterfly valve to the wide application of the butterfly valve, it has been a long time. Its advantage is that the price is lower than similar equipment. In a variety of strict and critical control pipeline processes, butterfly valves can be easily used as long as the choice is appropriate. Due to different market demands, the structure and function of the butterfly valve are constantly optimized, and the butterfly valve itself is constantly evolving and developing. Butterfly valves are classified in many ways. According to the valve structure, it can be divided into the middle line seal butterfly valve, the single eccentric butterfly valve, the double eccentric butterfly valve and the tri-eccentric butterfly valve. According to the sealing structure, it can be divided into metal seals, rubber lined and fluorine lined plastic soft seals. In addition, the metal seal can be a multi-layer seal structure or an elastic seal structure. The basic classification of butterfly valves is as follows.
(1) The concentric butterfly valve
The structure of the concentric butterfly valve is characterized by the integration of the stem axis, the butterfly plate center and the body center. It has a simple structure and a simple production process. The common rubber-the lined butterfly valve also belongs to this type. The disadvantage of concentric butterfly valves is that the disc and seat are always under pressure, which can cause rapid wear. The valve seat is generally made of rubber or polytetrafluoroethylene and other elastic materials.
(2) The single eccentric butterfly valve
Because there are static balance and other problems for the disc and seat of the concentric butterfly valve between the pressure, the single eccentric butterfly valve is generated. The single eccentric spy valve is designed to make the rod shaft deviate from the center of the butterfly plate, which can reduce the huge extrusion pressure. It is caused by the integration of the three cores to a certain extent, and significantly relieves the excessive extrusion between the upper and lower ends of the butterfly plate and the seat. The core problem is that the friction between the stack and the seat is not gone. It is not completely improved, so the valve not much is used.
(3) The double eccentric butterfly valve
The double eccentric butterfly valve is further improved based on the single eccentric butterfly valve. It is also the most widely used butterfly valve. The characteristic of its structure is that the stem shaft deviates from not only the center of the disc, but also the center of the body. The double eccentric effect of the soft seal butterfly valve makes the butterfly plate free from the seat immediately. After the valve is opened, it eliminates the unnecessary excessive pressure and friction between the butterfly plate and the seat, reduces the wear brought by friction and improves the effect of the seat. Scratch is greatly reduced. Metal seats can be used on the double eccentric butterfly valve. It improves the butterfly valve in the field of high-temperature application.
The outer rim of the butterfly plate and the sealing seat of the double eccentric butterfly valve are processed into a semi-spherical surface. The inner surface of the sealing seat is squeezed by the outer surface of the butterfly plate to produce elastic deformation to achieve the purpose of closing. The double eccentric butterfly valve usually uses tetrafluoroethylene as the sealing seat. It can also use the golden force sealing seat to expand its application in the high-temperature field. However, the seal of the metal sealing seat double eccentric butterfly valves still belongs to the position sealing structure, that is, the butterfly plate and the sealing surface of the seat contact. It cannot withstand high pressure. The valve will inevitably lead to high-pressure system leakage. Therefore, we should try to avoid the choice of metal sealing seat double eccentric butterfly valves.
(4) The tri-eccentric butterfly valve
The tri-eccentric butterfly valve mostly adopts a metal hard seal seat. It can deal with high-temperature limit problems. The butterfly plate is surrounded by a stainless steel plate. This kind of seal has the advantages of a hard metal seal and an elastic soft seal to deal with the leakage problem. Tri-eccentricity fundamentally change the sealing structure. It does not depend on the elastic deformation of the seat, but it completely depends on the contact surface pressure of the seat to achieve the sealing effect. Thus, we solve the metal seat zero leakage difficulties, the contact surface pressure and medium pressure positive correlation, high temperature and high-pressure resistance.
