Processing technology of Triple Offset Butterfly Valve
Compared with other valves, the Triple Offset Butterfly Valve
has shorter structure length, lighter weight, higher sealing performance, lower operating torque, faster opening and closing speed, and longer life. However, the sealing surface of the butterfly plate of the butterfly valve is generally a one-way pressure-bearing seal, that is, an inclined cone surface with a higher pressure within the strength range. The sealing performance is good, but the sealing performance of the back pressure bearing is poor. Generally, it does not exceed 0.5MPa, which limits the application of triple eccentric butterfly valves.
After analysis, the parts processing technology and consistency tolerance have been improved, and the three-eccentric butterfly valve can achieve two-way zero leakage.
1. Valve body processing The stem hole of the Triple Offset Butterfly Valve
and the stem hole of the valve body are usually processed by a mango bed. After installing the tool and the valve body in place to reduce the coaxiality error, place the dial indicator on the main shaft and rotate the main shaft to make the valve body passage symmetrical along the center line of the main shaft. correct. For holes, the tooling table is rotated 180° and a dial indicator is added to fix the other end of the channel boring.
2. The sealing surface of the disc plate eccentric butterfly valve is commonly used as a combined sealing ring, and the structure is "metal + graphite" and "metal + PTEE". When processing the sealing surface, put the board first. Assemble the seal and pressure ring, and process the sealing surface to the specified size with an inclined die. If the "metal + graphite" seal is processed, graphite will replace the metal craft seal. When processing "metal + PTFE", PTFE is easily deformed and affects the seal. Therefore, when processing, leave a margin of 0.8-1mm on the sealing surface of the butterfly plate, seal assembly, and pressure ring. Refer to the size of the drawing, even if the PTFE is deformed during the assembly process. , There is still room for adjustment.
3. Due to the structural limitation of the butterfly valve, the pressing force cannot be increased by increasing the length and number of screws. From the design point of view, the fit tolerance of the seal and the butterfly plate is -. The inner diameter tolerance of the PTFE seal ring can be changed to 59, and the disc positioning step tolerance can be changed to h9. In addition, for ease of assembly, the inner diameter tolerance of the metal seal ring is still D11. After the fit tolerance is changed, the clearance between the PTFE seal ring and the butterfly plate is small, and the compression shrinkage is suppressed. At the same time, decompressing the valve during the inspection also solved the problem of leakage at the valve seal.