This article mainly introduces the processing of metal hard seal butterfly valve components. Including valve body, butterfly plate processing, and seal pair tolerance selection.
1.Valve body processing
The processing of the stem hole of the butterfly plate of the three eccentric metal hard seal butterfly valve and the stem hole of the valve body is generally completed by boring on a boring machine. In order to reduce the coaxiality error, after the tooling and the valve body are in place, place a dial indicator on the main shaft, and correct the valve body channel symmetry along the main axis of the shaft by turning the main shaft. Add a dial indicator to calibrate the other end of the channel.
2. Plate processing
The sealing surface of triple eccentric metal hard seal butterfly valve generally adopts a combined seal ring, and the structure includes "metal + graphite" and "metal + PTEE". When processing the sealing surface, firstly assemble the disc plate, the sealing assembly and the pressure ring, and process the sealing surface to the size on the inclined die. If the "metal + graphite" sealing component is processed, graphite is replaced by a metal process sealing ring. If processing "metal + PTEE", PTEE is easily deformed and affects the sealing. Therefore, when machining, refer to the drawing size to reserve a machining allowance of 0.8 to 1 mm for the sealing surface of the plate, seal assembly and pressure ring assembly, so that even when PTEE is assembled, Deformation also has room for adjustment.
3.Tolerance selection of sealing pair
When the sealing component is a "metal + PTFE" structure, the seal does not leak during the pressure test, and it leaks when the pressure is released. The larger the caliber, the higher the pressure, the more obvious the phenomenon. After loosening the screws that tightly seal the assembly, the test pressure is re-compressed, and the above problem occurs again. The reason is that during the test pressure, the seal assembly is contracted due to the increase of the sealing pressure. When the pressure is released, the PTFE seal ring cannot return to its original state and leaks. Due to the limitation of the butterfly valve structure, the method of increasing the length and number of screws cannot be used to increase the pressing force.