Analysis of sealing force of two-way pressure butterfly valve
1, mainly composed of valve body, disc, valve stem and filler. Eccentric distance between the center of rotation of the valve stem and the sealing surface of the valve body When the eccentric butterfly valve is in the forward flow of the medium to achieve the sealing function, the necessary sealing force applied by the stem torque on the sealing surface of the disc is FMF(N). However, due to the action of the medium force FMJ(N), the actual sealing force of the sealing surface is increased to FMZZ. At this time, the actual sealing force FMZZ of the sealing surface is the sum of the necessary sealing force FMF and the medium force FMJ.
The force exerted by the valve stem on the sealing surface of the disc during reverse sealing is the sum of the necessary sealing force and the medium force. When the reverse sealing is applied, the force exerted by the valve stem on the sealing surface of the disc is greater than that of the valve stem during the positive sealing. force.
Analysis of the influence of the bending deformation of the valve stem of two-way pressure butterfly valve on the seal
Since the force exerted by the valve stem on the sealing surface of the butterfly plate during reverse sealing is greater than the force of the valve stem during the positive sealing, the sealing effect of the valve stem bending deformation on the eccentric butterfly valve is analyzed only for the reverse flow of the medium. When the medium flows in the opposite direction, the valve stem overcomes the force of the sealing surface and overcomes the positive pressure of the medium force on the valve stem. The force of the two-way pressure butterfly valve stem is reduced to a simple beam.
Due to the combined action of the sealing force and the force of the medium, the valve stem is bent and deformed. When the medium is flowing forward, the valve stem is bent toward the sealing surface, and the deformation of the valve stem is advantageous for sealing. When the medium flows in the opposite direction, the valve stem is bent away from the sealing surface, and the butterfly plate is bent away from the sealing surface as the valve stem is bent, and the sealing force is reduced, and the sealing cannot be ensured. It can be seen from the above analysis that when the medium flows in the reverse direction, the eccentric butterfly valve cannot guarantee a reliable sealing function due to the reverse action of the medium force. In order to solve this problem, we have developed a new type of bi-directional metal hard seal butterfly valve.
The upper and lower wedge shafts of the two-way pressure butterfly valve are arranged on the upper and lower parts of the valve cavity, and the cross-sectional area of ​​the upper and lower wedge axes is appropriately increased, that is, the moment of inertia I is increased, the rigidity of the valve stem is increased, and the deformation amount δ2 is decreased. Does not make the fluid resistance of the butterfly valve too large. When the matching clearance between the upper and lower wedge shaft holes and the valve stem is greater than or equal to the deformation amount δ2, the deformation of the upper and lower wedges does not cause bending deformation of the valve stem.
The upper and lower wedges further push the valve stem to increase the wedge force of the wedge block, and the butterfly plate obtains a larger sealing force, which can compensate for the slight movement of the butterfly plate to the sealing surface caused by the deformation amount δ2, and improves the reverse direction. The reliability of the seal.
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