Field Overlay Weld Repair of CLF140-65 Roller Press Roller Surface

Literature Overview

This paper by Xu Minghua, Wang Xin, Li Junwei, and Huang Zhiquan, published in New Century Cement Herald (2007, Vol. 13, No. 5, pp. 38-39), documents the field overlay weld repair of roller surfaces on CLF140-65 roller presses used in a 2500 t/d cement production line at Suzhou Dongwu Cement Co., Ltd. The paper provides a practical account of how overlay welding technology can extend the service life of critical grinding equipment in cement production, addressing a common operational challenge in the cement industry.

The CLF140-65 roller press is a key component in the joint grinding system that combines a roller press with a ball mill (φ3.8 m × 12 m) for cement grinding. This configuration offers significant advantages over traditional ball mill-only systems, including reduced power consumption, increased mill throughput, improved cement quality, and lower noise levels. However, the roller surface is subject to severe abrasive wear during operation, and when wear becomes excessive, the grinding efficiency degrades significantly, necessitating repair or replacement.

Core Technical Content

Roller Press Operating Conditions

The roller press operates under extreme conditions that accelerate roller surface wear:

The roller surface is subjected to a combination of compressive loading, sliding friction, and impact loading from the feed material. The wear mechanism is primarily abrasive, with hard particles in the cement clinker or raw meal embedding into the roller surface and plowing material away. This results in progressive loss of the roller surface profile, which degrades the grinding efficiency and increases power consumption.

Overlay Weld Repair Process

The field repair process involves several critical steps:

1. Surface preparation: The worn roller surface is ground to remove loose material, rust, and contaminants. The surface is prepared to a roughness of Ra 6.3-12.5 μm to ensure good weld adhesion.
2. Welding consumable selection: Hardfacing electrodes or wires with appropriate hardness and wear resistance are selected based on the operating conditions and desired service life.
3. Welding process: Manual or mechanized arc welding is used to apply the overlay layer. The welding parameters are optimized to achieve good fusion with the base metal while minimizing dilution.
4. Post-weld treatment: The overlay surface is ground to restore the original roller profile and surface finish.
5. Inspection: Visual inspection and dimensional checks ensure the repair meets specifications.

Welding Consumables and Parameters

The selection of welding consumables is critical for achieving the desired hardness and wear resistance:

The welding parameters are optimized to achieve:

• Adequate penetration into the base metal for strong fusion
• Minimal dilution to maintain overlay hardness
• Uniform weld bead profile for subsequent grinding
• Low residual stress to prevent cracking

Engineering Practice Integration

Field Repair vs. Replacement

The decision between field repair and roller replacement involves a cost-benefit analysis:

For the Suzhou Dongwu Cement application, field repair was selected because the roller body was still in good condition, with only the surface layer worn. The cost savings and reduced downtime justified the field repair approach, even though the service life was somewhat shorter than a new roller.

Quality Control Challenges in Field Conditions

Field repair presents unique quality control challenges:

• Environmental conditions: Dust, temperature variations, and humidity can affect weld quality.
• Equipment limitations: Portable welding equipment may not provide the same stability as factory equipment.
• Operator skill: Field operators may have varying levels of experience with overlay welding.
• Inspection limitations: Full non-destructive testing may be impractical in field conditions.

To address these challenges, the following measures are recommended:

1. Establish a controlled welding environment with shelter and ventilation.
2. Use preheating and interpass temperature control to minimize cracking risk.
3. Implement a qualified operator program with regular skill assessment.
4. Perform visual inspection and dimensional checks after repair.
5. Monitor the repaired roller during the first few weeks of operation for signs of early failure.

Performance Monitoring

After the repair, the roller performance should be monitored to verify the effectiveness of the overlay weld:

• Grinding efficiency: Compare the power consumption per ton of cement ground before and after repair.
• Product quality: Monitor the particle size distribution and fineness of the cement product.
• Roller surface condition: Periodically inspect the roller surface for wear patterns and defects.
• Service life: Track the operating hours until the next repair or replacement is required.

Key Questions and Reflections

The paper raises an important question about the long-term reliability of field-repaired rollers. While the initial repair restores the roller to acceptable condition, the overlay weld layer may have different wear characteristics than the original factory-applied surface. The dilution between the overlay and base metal can affect the hardness and wear resistance of the repair layer, and the residual stress from field welding can influence the fatigue life of the roller.

Another consideration is the effect of the repair on the roller's dynamic balance. If the overlay weld is not applied uniformly around the roller circumference, it can create an imbalance that causes vibration during operation. This is particularly critical for high-speed roller presses where even small imbalances can lead to significant vibration and bearing damage.

In my experience, the success of field overlay weld repair depends heavily on the discipline of the repair process. A well-documented procedure, qualified operators, and thorough inspection can achieve results that are comparable to factory repair. However, cutting corners on any of these elements can lead to premature failure and increased downtime.

Study Insights and Implications

This paper provides a practical case study of overlay weld repair in the cement industry, demonstrating the economic and operational benefits of extending the service life of critical equipment through welding. The CLF140-65 roller press repair at Suzhou Dongwu Cement illustrates how overlay welding technology can be applied to large, heavy components in field conditions.

The key takeaway for engineers is that field repair is a viable alternative to replacement when the base component is in good condition and the wear is primarily superficial. However, the repair must be executed with the same rigor as factory repair, with attention to surface preparation, consumable selection, welding parameters, and quality inspection.

The paper also highlights the importance of post-repair monitoring. The repaired roller should be closely observed during the first few weeks of operation to detect any signs of early failure, such as unusual vibration, increased power consumption, or changes in product quality. This monitoring period is critical for validating the repair and identifying any issues that require corrective action.

In conclusion, the field overlay weld repair of roller press surfaces is a cost-effective and practical solution for extending the service life of critical grinding equipment in cement production. The success of this approach depends on proper planning, qualified execution, and thorough quality control.