In terms of seal principle, mechanical seals for cauldron and discharge trough are the same as mechanical seals for pump, but they share common operating conditions and operating techniques with mechanical seals for pump. Therefore, requirements of seal structure design and seal system are different from mechanical seals for pump and have their own characteristics:
1. The inner diameter oscillation and axial channeling of the stirring shaft are large
Kettle, discharge chute shaft for vertical structure, large diameter of axle, respectively for Φ178 and Φ120 mm , suspension of cauldron-using machinery sealing arm length, when mixing, material yield of eddy current in addition to the level of activity, will happen in the direction of up and down cycle activities, therefore, lead to the stirring shaft radial oscillation.In addition, the axial thrust generated by stirring, the self-weight of stirring shaft and the axial load superimposed by material pressure lead to axial channeling. These factors can easily lead to poor sealing of sealing end face, unstable liquid film, and sometimes crack soft sealing environment, resulting in failure of mechanical sealing of reactor.
2. Gas-phase seal
Most of the sealing medium used for mechanical sealing of caulk and discharge trough is gas, rather than liquid. As the material in the caulk is usually not full cauldron, as long as the material is full caulk, it is liquid. Therefore, the seal working condition is severe during operation.
3. Variable operating mode operation
The material is subjected to chemical reaction in the reactor. The process is that the temperature and pressure drop from high temperature and high pressure to normal temperature and pressure.When the new material enters the kettle, the temperature pressure in the kettle returns to high temperature and high pressure.The repeated substitution changes of pressure and temperature bring a poor seal working condition, which is easy to cause hydraulic and thermal deformation of mechanical seal end face, resulting in leakage of seal end face.At the same time, the repeated change of temperature pressure is also easy to accelerate the aging deformation of the auxiliary sealing ring, resulting in failure of sealing.
4. Easy sealing and disassembly
Reaction kettle is usually vertical equipment, and its installation method: electric type - reducer - frame - reaction kettle.The mechanical seal is between the caulk flange and the coupling of the frame so that the mechanical seal can be replaced by an axial neutral between the two shafts.The cauldron is assembled with a flange, a shaft sleeve, a short shaft and a mechanical seal. It can be repaired by itself outside the cauldron and then replaced directly, so it is easy to be assembled and disassembled.The mechanical seal is directly installed on the rotating shaft. The upper end of the seal is supported by two propulsion bearings. When mounting and dismounting, the motor and frame should be removed.
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