10/8F-AH Large Slurry Pump Bearing Clearance Adjustment: Comparison of Cold Shrink and Hot Expansion Methods

Subtitle: Operation points, application conditions, and clearance control for liquid nitrogen cooling vs. oil bath heating

Introduction

The 10/8F-AH is a large model in the AH series (250mm discharge, 200mm inlet), widely used in large-scale mill discharge and long-distance tailings transport. Its bearing assembly withstands high radial and axial loads, and installation quality directly affects vibration, stability, and service life. Bearing clearance adjustment is critical – excessive clearance causes vibration and noise; insufficient clearance leads to overheating and seizure.

Large bearings (inner diameter >100mm) are typically mounted with interference fit on the shaft. Two field methods are common: cold shrink (liquid nitrogen cooling) and hot expansion (oil bath heating). As a professional slurry pump manufacturer, this article compares the principles, procedures, application conditions, and clearance control for both methods.

1. Bearing Clearance: Concept and Importance

Bearing clearance is the internal gap between rolling elements and raceways before mounting. For 10/8F-AH pumps, heavy-duty spherical roller bearings with C3 or C4 clearance class are typically used.

Key point: Mounting clearance must be within design range. Too small → negative clearance after temperature rise → bearing burnout. Too large → increased rotor runout → accelerated seal and impeller wear.

2. Cold Shrink Method (Liquid Nitrogen)

2.1 Principle

Submerge the bearing in liquid nitrogen (-196°C) to contract its inner diameter, creating sufficient assembly clearance to slide onto the shaft. Cooling time is typically 15-30 minutes depending on bearing size.

2.2 Procedure

2.3 Applicability, Pros & Cons

3. Hot Expansion Method (Oil Bath Heating)

3.1 Principle

Heat the bearing in an oil bath to 80-120°C, expanding its inner diameter to slide onto the shaft. Temperature must be strictly controlled – never exceed 120°C (otherwise bearing steel tempering reduces hardness).

3.2 Procedure

3.3 Applicability, Pros & Cons

4. Cold Shrink vs. Hot Expansion: Comparison Table

5. Field Clearance Adjustment for 10/8F-AH Bearings

After mounting (cold or hot), clearance must be checked. 10/8F-AH typically uses 22324CA/W33 or similar spherical roller bearings. Recommended mounting clearance: 0.05-0.10mm (refer to manufacturer manual).

5.1 Clearance Measurement Methods

5.2 Clearance Adjustment

6. Common Field Installation Mistakes and Prevention

7. Case Study: Bearing Hot Expansion Retrofit at an Iron Mine

Background: A 10/8F-AH pump at an iron mine experienced frequent bearing overheating (>90°C), requiring replacement every 3 months.

Diagnosis: Original installation used oil bath heating to 140°C (excessive), causing hardness loss; mounting clearance was too small (<0.02mm).

Improvements:

• Strictly controlled heating temperature to 100-110°C

• Adjusted mounting clearance to 0.06-0.08mm

• Switched to C3 clearance class bearings

Results: Bearing operating temperature dropped to 65°C, bearing life extended to over 12 months.

Conclusion

For 10/8F-AH large slurry pump bearing clearance adjustment, both cold shrink and hot expansion have advantages. Cold shrink is ideal for large bearings, batch mounting, and has no metallurgical risk, but requires LN₂ supply. Hot expansion uses common equipment and has lower cost, but requires strict temperature control. Regardless of method, always measure clearance after mounting and ensure it is within design range.

As a professional slurry pump manufacturer, we recommend field maintenance personnel choose the appropriate method based on bearing size, site conditions, and safety requirements, and strictly perform clearance checks. For bearing installation training or technical guidance, please contact our engineering team.