In the static soaking experiment, the sealing device of the reaction kettle needs to combine static sealing and dynamic sealing technologies, and choose the appropriate sealing form and material according to the specific working conditions. The following is a detailed explanation:
Core types and selection criteria of sealing devices
static seal
Application scenarios: Fixed parts such as the connection between the kettle body and the kettle cover, manholes, and connecting ports.
Sealing principle: Sealing is achieved by compressing and deforming gaskets (such as metal wrapped gaskets, rubber/PTFE coated gaskets, graphite gaskets, etc.) to fill the gap between flange surfaces.
Design points:
The flange surface form needs to be matched (such as RF surface, FF surface, MFM surface) to ensure the flatness and smoothness of the contact surface.
The pre tightening force of the bolts should be uniform to avoid local stress concentration leading to leakage.
The gasket material needs to be compatible with the medium, temperature, and pressure (such as graphite pad for high temperature resistance and PTFE pad for corrosion resistance).
Dynamic seal
Application scenario: The sealing between the rotating stirring shaft and the kettle body is a key and difficult point in static immersion experiments.
Common forms:
Mechanical seal: composed of dynamic ring, static ring, auxiliary sealing ring, spring, etc., it achieves zero leakage through precise fitting and is suitable for high-pressure, high-temperature, and corrosive media.
Packing seal: By applying axial pressure to the packing chamber through a pressure cap, the packing expands radially and adheres tightly to the shaft and the inner wall of the packing box. The structure is simple but the leakage rate is large, requiring the design of a leakage port and the connection of a treatment device.
Magnetic driven sealing: The motor power is transmitted into the kettle through magnetic coupling, achieving isolation between the stirring shaft and external transmission. It is suitable for highly toxic, highly corrosive, or high-purity media, but the cost is relatively high.
Key points for installation and maintenance of sealing devices
Pre-installation preparation
Component inspection: Ensure that the sealing surface is smooth, flat, and free of scratches, cracks, or corrosion; Check the radial runout and axial displacement of the mixing shaft to ensure compliance with design requirements.
Cleaning treatment: Clean the interior and sealing components of the equipment to avoid contamination of the sealing surface by impurities such as oil, dust, and welding slag.
Material matching: Select sealing materials (such as stainless steel, Hastelloy alloy, silicon carbide, polytetrafluoroethylene, etc.) based on the properties of the medium (such as acidity, alkalinity, oxidation), temperature, and pressure.
Installation process control
Static seal installation:
Tighten the flange bolts diagonally and symmetrically, gradually applying force multiple times to ensure even force and avoid tilting the kettle cover.
Control the tightening torque within the specified range (such as 40~120N · m) to prevent the sealing surface from being squeezed or overloaded for wear.
Installation of dynamic seal:
Mechanical seal: Apply lubricating oil or grease to the friction surface of the dynamic and static rings to reduce initial starting friction; Install the static ring, dynamic ring, spring system, and other accessories in sequence, and use a torque wrench to tighten the bolts to the specified torque value.
Packing sealing: Regularly adjust the pressure of the gland, replace aging packing, and ensure the sealing effect.
Magnetic driven seal: Ensure good coupling between the outer magnet and the inner rotor, and compatibility between the isolation sleeve material and the medium.
Operation monitoring and maintenance
Regular inspection: Check the sealing status (such as signs of leakage, abnormal temperature, abnormal noise, etc.), tighten the flange bolts (cold tightening, hot tightening), replace the packing or vulnerable parts of the mechanical seal.
Performance testing: Verify the sealing performance through pressure testing (using compressed air or inert gas to maintain pressure), water pressure testing, or helium leak detection (using helium mass spectrometer to locate small leak points).
Troubleshooting: Stop the machine immediately upon discovering a leak, check the installation of the sealing components, and reinstall or replace the seals if necessary.
Optimization suggestions for static immersion experiments
Material selection: If the experimental medium is a highly corrosive liquid (such as concentrated sulfuric acid or sodium hydroxide), PTFE or Hastelloy sealing materials are preferred; If the medium is a high-temperature liquid, high-temperature resistant materials such as graphite and silicon carbide should be selected.
Sealing form: For static immersion experiments without stirring or at low speeds, a combination of static sealing and packing sealing can be used to reduce costs; For experiments that require stirring or high-speed rotation, mechanical seals or magnetic driven seals should be used to ensure sealing reliability.
Environmental control: The installation environment should be kept clean and dry to avoid dust and moisture affecting the sealing quality; The temperature and humidity must meet the equipment requirements to ensure stable sealing performance.