Butterfly valve is one of the most rapidly growing type valve in recent years, with the development of industrial technology, the applicable scope of the butterfly valve is more and more widely, the type and quantity expanding, and resistance to high temperature and high pressure, high sealing, large diameter, long service life, adjust the direction of the excellent features and multifunctional. There are many ways to classify butterfly valves. TakeTrieccentricity butterfly valveas an example to analyze the installation direction in detail.

Triple eccentric butterfly valve structure schematic diagram

Structural features of three-eccentric butterfly valve:
The center of disc rotation (i.e. the center of valve shaft) forms A offset on the sealing section of the valve plate and A b offset with the center of valve body. Valve body sealing cover center line and seat center line (i.e. valve body center line) form an Angle offset for Angle.
Three eccentric butterfly valve installation direction
According to the arrow on the valve body,triple eccentricity butterfly valve can be installed in three cases.
In the first case, the arrow indicating the flow direction of the medium has been indicated on the butterfly valve body, which should be installed in the direction indicated by the flow direction.
In the second case, no direction is indicated on the butterfly valve body. At this point, the valve manufacturer's manual should be consulted to determine the type of butterfly valve, and then according to the valve structure to determine whether there are installation direction requirements, if it is eccentric butterfly valve should be paid attention.
The third case, the pressure shown on the butterfly valve body in the direction of the arrow (the end of the arrow indicates that the pressure side), if the construction personnel during installation as the medium flow arrow way installation, is certainly will cause the valve sealing, reduce the service life of the valve.
In actual production process, triple eccentric butterfly valve plate side to low voltage side, the side of the valve shaft for the high side, namely the pressure side, on both sides of the valve pressure at the same time, not conducive to the valve locked, conform to the work requirements of triple eccentric butterfly valve.
Butterfly valve installation direction analysis
Imported trieccentric metal sealing butterfly valve usually has its recommended installation direction, not recommended reverse installation; The manufacturing process of eccentricity butterfly valve in China is relatively poor, usually one leakage level or one or two pressure levels are one or two lower than the forward one. The reasons are as follows:
A. It depends on the structure of the butterfly valve. The sealing structure of the middle line sealing butterfly valve determines its double side pressure bearing capacity is the same, so the middle line sealing butterfly valve has no requirement for flow direction. Eccentric butterfly valve (including eccentric eccentric single, double and triple eccentric butterfly valve) mostly have requirement to flow, even a two-way sealing is positive and negative two directions can meet the sealing requirements under the rules of stress level, one must have a side can withstand higher pressure, make better in sealing.
B. Easy maintenance. Eccentric butterfly valves usually have high pressure side on the valve shaft side and low pressure side on the valve plate side. Once installed, the valve will leak out during overhaul.
C. It is conducive to sealing butterfly valve and preventing internal leakage. The sealing between the seat of the three-eccentric butterfly valve and the sealing cover of the valve plate is achieved by pressing the disc against the seat through the torque of the actuator. The higher the medium pressure is, the tighter the sealing pressure is. The sealing begins to leak when the positive unit pressure between the seat and the disc is less than the medium pressure as the medium pressure increases.
3 conclusion
The principle and structure of butterfly valve seal are discussed in this paper. By the analysis of the eccentric butterfly valve triple eccentric butterfly valve, in particular, although the nominal valve manufacturer for two-way sealing, with no requirement for installation direction, but its just reverse the sealing ability of under pressure to increase, still can't positive under pressure. For triple eccentric butterfly valve, from the power of the maintenance sealing Angle consideration, suggest that it is a direction of the installation, choose the right installation direction is not only beneficial to the valve seal, valve protection, prolong the service life of the valve, also can avoid the potential safety hazard to the greatest extent.