Internal mixer rotor end face seals mainly use two structures: mechanical seals and labyrinth seals. Mechanical seals are the mainstream choice for modern high-efficiency internal mixers. Hansheng Automation can machine dynamic rings, stationary rings, springs, O-ring grooves, and carbide mating rings from customer drawings, in single pieces or small batches.
1. Mechanical seal
Structure: It consists of a dynamic ring, a stationary ring, a spring, and an auxiliary sealing ring such as an O-ring. The dynamic ring rotates with the rotor. The stationary ring is fixed to the frame. Spring force keeps the two ring faces in tight contact for sealing.
Key parameters:
Face pressure: usually 0.3 to 0.6 MPa
Spring pressure: 0.05 to 0.2 MPa
Linear speed: ≤20 m/s for high-viscosity compound conditions
Leakage rate: <10 mL/h, as required by GB/T 14211-2019
Applications: high temperature ≤200 °C, high pressure ≤2.5 MPa, and precision mixing conditions that require zero leakage, such as medical and food-grade rubber production.
2. Labyrinth seal
Structure: Multiple stages of tortuous clearance between the rotor and seal cover create fluid resistance for sealing. It is a non-contact seal with no mechanical wear.
Features:
Allows larger axial movement: ±2 mm
Strong resistance to particulate impurities
Higher leakage: about 200 to 500 mL/h
Suitable for low speed and room temperature conditions
3. Comparison
| Feature | Mechanical seal | Labyrinth seal |
|---|---|---|
| Sealing principle | Face contact sealing | Clearance throttling sealing |
| Leakage | <10 mL/h | 200 to 500 mL/h |
| Temperature resistance | ≤200 °C | ≤120 °C |
| Allowable axial movement | ±0.5 mm | ±2 mm |
| Maintenance interval | 6 to 12 months, replace dynamic ring | 24 months or more, cleaning only |
| Applicable pressure | ≤2.5 MPa | ≤0.8 MPa |
4. Selection advice
Polymer mixing, such as TPE and TPU: prefer a double mechanical seal with a heat transfer oil flushing system to prevent material carbonization.
Carbon black filled compound: use a mechanical seal with carbide mating rings. Wear resistance increases more than 3 times. We can machine carbide mating rings and other wear parts from drawings.
Low speed large internal mixer, rotor speed <30 rpm: a labyrinth seal plus exhaust recovery device can be used.
Note: When replacing seals, check rotor axial movement. It must be ≤0.3 mm. If out of tolerance, adjust the thrust bearing. Otherwise, the mechanical seal will wear abnormally.
Beyond internal mixer seals, our precision custom machining capability is not limited to one industry. Hansheng Automation can machine functional parts for filling machinery, printing machinery, and food machinery from customer drawings. We also machine yacht components, RC car components, and non-standard metal parts for tobacco packaging machinery and medical devices. We focus on build-to-print custom machining and produce single pieces or small batches according to customer drawings. We do not sell complete machines.
