1,Preparation Before Replacement
Adequate preparation is the foundation for smooth replacement. Neglecting this step may lead to operational delays or safety hazards.
Safety First
Cut off the mixer's power supply and lock the switch, hanging a "No Operation" sign to prevent accidental startup.
Relieve residual pressure in the equipment (e.g., hydraulic or pneumatic systems) and confirm that the mixing shafts are completely stationary.
Wear personal protective equipment (PPE): anti-cut gloves, safety shoes, goggles, and dust masks (to avoid inhalation of residual materials).
Clean the Work Area
Remove residual materials in the mixer drum (use tools like shovels or high-pressure water to clean adhered materials) to prevent debris from falling into the seal installation area during replacement.
Clean the surface of the shaft end, flange, and surrounding components with a wire brush or degreaser to remove oil, rust, or material deposits.
Prepare Tools and Spare Parts
Tools: Socket wrenches, screwdrivers, pliers, seal pullers, torque wrenches, feeler gauges, and cleaning cloths.
Spare Parts: Confirm that the new shaft end seals match the mixer model (check specifications such as inner diameter, outer diameter, and material; common materials include nitrile rubber, fluororubber, or PTFE, selected based on the mixed material's properties).
Auxiliary Materials: High-temperature resistant grease (for lubricating the seal lip), thread locker (to prevent bolt loosening), and rust inhibitor (for exposed metal surfaces).
2,Removal of Old Seals
Improper removal may damage the shaft, flange, or other components, affecting the new seal's performance.
Disassemble External Components
Remove protective covers, retaining rings, or pressure plates fixed to the shaft end in sequence. Record the assembly position of each part (take photos if necessary) to avoid errors during reinstallation.
For bolts or screws that are rusted or stuck, apply penetrating oil and wait 10–15 minutes before loosening; do not use brute force to prevent thread stripping.
Remove the Old Seal
Use a seal puller or flat-blade screwdriver (wrapped with tape to avoid scratching the shaft surface) to gently pry the old seal from the housing. Do not tilt the tool excessively to prevent damage to the shaft's surface finish (even minor scratches can cause oil leakage).
After removal, check the shaft, seal seat, and flange for wear, cracks, or deformation:
If the shaft surface has scratches or rust, polish it with fine sandpaper (400–600 grit) until smooth; severe damage requires shaft repair or replacement.
If the seal seat (housing) is worn or has grooves, use a reamer to repair it (within the allowable tolerance) or replace the housing.
3,Installation of New Seals
Correct installation directly determines the sealing effect. Pay attention to alignment, tightness, and protection of the seal lip.
Check and Prepare New Seals
Inspect the new seal for defects: no cracks, deformation, or damage to the lip (the lip is the core sealing part; even minor nicks can cause leakage).
Apply a thin layer of matching grease to the seal lip and the contact surface of the shaft end (grease should be compatible with the seal material to avoid swelling or hardening).
Install the New Seal
Ensure the seal is oriented correctly: the lip (the flexible, inwardly curved part) must face the direction of the material or fluid to be sealed (e.g., toward the mixer drum to block material leakage).
Use a sleeve (with an inner diameter slightly larger than the shaft and outer diameter matching the seal) to press the seal into the seat evenly. Do not tap the seal directly with a hammer (to prevent deformation); apply force uniformly to the seal's end face.
After installation, check that the seal is fully seated in the seat, with no tilting (use a feeler gauge to measure the gap between the seal and the seat flange; the gap should be uniform around the circumference).
Reinstall External Components
Reassemble the pressure plate, retaining ring, and protective cover in the reverse order of disassembly, referring to the earlier photos or records.
Tighten bolts with a torque wrench according to the manufacturer's specified torque (over-tightening may deform the seal; under-tightening may cause loosening and leakage). Apply thread locker to bolt threads if necessary.
4,Post-Installation Inspection and Testing
After replacement, verify the installation quality to ensure no hidden issues.
Visual Inspection
Check that all components are properly installed: no missing bolts, no loose parts, and the seal lip is in close contact with the shaft surface.
Confirm that there is no debris (such as tools or rags) left in the work area.
Test Run
Conduct an empty test run first: power on the mixer and run it at low speed for 5–10 minutes, observing for abnormal noise (indicating possible friction between the seal and shaft) or oil leakage at the shaft end.
Perform a load test: add a small amount of material and run the mixer. After stopping, check for material leakage at the seal and whether the seal lip remains intact (no displacement or damage).
Post-Test Maintenance
Wipe off excess grease or oil around the shaft end.
Record the replacement date, seal model, and test results in the equipment maintenance log for future reference.