Structural Analysis of Three Eccentric Metallic Sealing Butterfly Valve

Analysis of Three Eccentric Metallic Sealing Butterfly Valve

As a valve used to realize on-off and flow control of piping system, butterfly valve has been widely used in many fields such as petroleum, chemical industry, metallurgy, hydropower and so on. In the well-known butterfly valve technology, the sealing structure adopts the sealing structure, the sealing material is rubber, polytetrafluoroethylene and the like. Due to the structural characteristics of the restrictions, do not meet the high temperature, high pressure and corrosion-resistant, anti-wear and other industries.

A more advanced butterfly valve is a three-eccentric metal seal butterfly valve , the valve body and the valve seat as a single component, seat sealing surface layer surfacing temperature, corrosion resistant alloy material. Multi-layer soft stacked ring fixed to the valve plate, this butterfly valve compared with the traditional butterfly valve with high temperature, light operation, opening and closing without friction, closed with the torque of the transmission mechanism to compensate for increased sealing, improved butterfly valve The sealing performance and extend the service life of the advantages.

The butterfly valve with three eccentric multi-layer metal seal structure, no mechanical wear, zero leakage can be achieved, with excellent two-way sealing function, is used in petroleum, chemical, metallurgy, electricity, food, medicine, water supply and drainage, gas transmission and other media Of the pipeline to regulate the flow, the best device to cut off or connect the fluid. Choose different materials, can be applied to water, sewage, sea water, air, steam, gas, combustible gas, corrosive media, oil and food and other media, the maximum operating temperature up to 600 ℃.

Three eccentric metal seal butterfly valve structure

Three eccentric metal seal butterfly valve product features

Three eccentric structure: the stem axis and disc sealing surface offset a size A, and the valve body channel axis offset by a size B, the valve seat rotation axis and the valve body channel axis to form an eccentric angle α, so the formation of three eccentric . When the butterfly valve is opened from 0 ° to 90 °, the sealing surface of the butterfly plate will be released from the sealing surface of the valve seat immediately at the moment of opening. When the butterfly valve is closed from 90 ° to 0 °, the butterfly cone sealing surface will be closed only at the moment of closing Contact and pinch the seat conical seal. Therefore, there is no friction between the seat and the sealing surface on the disc, eliminating the possibility of wear and tear.

However, this butterfly valve still has the following problems during its use:

First, the multi-layer soft and hard stacked ring fixed to the valve plate, when the valve plate normally open state of the sealing surface to form a positive erosion, sheet metal sandwich in the soft seal by the erosion, directly affect the sealing performance.

Second, by the structural conditions of the structure does not adapt to do the following DN200 valve, because the overall structure of the valve plate is too thick, large flow resistance.

Third, due to the principle of three eccentric structure, the seal between the sealing surface of the valve plate and the valve seat is pressed against the valve seat by the torque of the transmission device. The positive flow state, the higher the media pressure seal squeeze tight. When the flow medium countercurrent media pressure increases with the pressure between the valve plate and valve seat unit pressure is less than the medium pressure, the seal began to leak.

High-performance three-eccentric two-way hard sealing butterfly valve, characterized in that: the seat ring by the soft T-ring seal on both sides of multi-layer stainless steel sheet. The sealing surface of the valve plate and the valve seat is an oblique conical structure, and a temperature-resistant and corrosion-resistant alloy material is deposited on the oblique conical surface of the valve plate; the spring fixed between the adjusting ring plate and the adjusting bolt on the pressure plate is arranged together.

This structure effectively compensates for the tolerance band between the sleeve and the valve body and the elastic deformation of the valve stem under the medium pressure and solves the sealing problem existing in the process of transporting the valve in the bidirectional interchangeable medium. The soft T-shaped multi-layer stainless steel sheet on both sides of the seal ring, with the advantages of both metal seal and soft seal, both in low temperature and high temperature conditions, have zero leakage of sealing performance.

Experiments show that pool positive flow state (medium flow direction and disk rotation in the same direction), the sealing surface pressure is the torque of the actuator and the media pressure generated by the role of the valve plate. Positive media pressure increases when the valve plate oblique cone surface and seat sealing surface squeeze the more tight, the better the sealing effect. In counter-current conditions, the seal between the valve plate and the valve seat presses the valve plate against the valve seat due to the moment of the drive. As the pressure of the reverse medium increases, the positive pressure between the valve plate and the valve seat is less than the pressure of the medium. The deformation stored by the spring of the adjusting ring after the load is absorbed can compensate for the tight pressure on the sealing surface of the valve plate and the valve seat Play a role in automatic compensation. Therefore, unlike the prior art, the utility model has the advantages that the soft and hard multi-layer sealing ring is mounted on the valve plate and is directly mounted on the valve body, and an adjusting ring is provided between the pressing plate and the valve seat which is a perfect bidirectional hard sealing method . It will replace gate valves, globe valves and ball valves.

Three eccentric metal seal butterfly valve works:

A typical three eccentric metal butterfly valve seal, in addition to the valve stem and the valve plate has two eccentric, valve plate and valve seat sealing surface of a ramp shape (which is the so-called third eccentric eccentric). When the valve is closed, the valve plate is pushed forward due to eccentricity, the valve plate and the valve seat do not generate friction in the closing process, and the valve plate directly presses on the valve seat, thus ensuring the service life of the valve; in addition, Of the sealing ring (whether installed on the valve seat or on the valve plate) has a certain elasticity, and the elastic ring with a small gap between the boss and the elastic ring can make a slight displacement of the elastic ring; when the valve is closed, by Close the role of force, elastomeric seals can be automatically moved to the most uniform force position; together with a small amount of deformation of the elastic ring, the valve seat at the seal uniform force to achieve the best seal.

Different eccentric structure of the butterfly valve performance changes: the number of eccentric valve plate increases, the thickness of the valve plate is also thickened, the fluid flow through the three eccentric butterfly valve resistance increases; with the butterfly valve eccentricity increases, the valve performance also has great changes. From the comparison of four different structural butterfly valves, it can be seen that the triple eccentric butterfly valve can generate larger pressure drop and can be used as a regulating valve; the pressure drop of the fluid flowing through the valve increases with the increase of the eccentricity number; however, Non-butterfly valve compared to three eccentric butterfly valve pressure drop is still relatively small. With changes in the number of eccentric butterfly valve seat sealing performance also will change, three eccentric butterfly valve has excellent seat sealing performance. As the number of eccentricities increases, the torque required for valve opening and closing decreases, so the torque required for opening and closing a three-eccentric butterfly valve is much smaller than that of other types of butterfly valves. With the changes in the number of eccentricity, the temperature and pressure range of the butterfly valve and temperature range will have a greater change, three eccentric butterfly valve temperature and pressure levels for the range of other types of butterfly valve unmatched.

Three eccentric butterfly valve advantages: good cutting performance Three eccentric metal sealing butterfly valve using torque off valve, so the valve seat has excellent sealing performance, it was called a zero leakage valve. The solid particles or dirt contained in the media have no significant effect on the shut-off performance of a three-eccentric metal seal butterfly valve because the medium flows at a high velocity close to the valve , preventing dirt from accumulating at the valve seat.

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