Arc Surfacing and Special Alloy Electroplating Repair of Paper Making Dryer Cylinders and Steam Balls

Literature Overview

This 1999 paper by Liu Jifeng and Li Lin, published in the journal "Surface Technology" (Volume 28, Issue 2, pages 32-33), reports on a combined repair technology for paper making dryer cylinders and steam balls (steam chests) using arc surfacing welding and special alloy electroplating. The work was implemented at the Xinxiang No. 2 Paper Mill and validated over nearly five years of practical operation. The paper is classified under TS734, indicating its relevance to paper making equipment engineering.

Problem Statement and Technical Background

Paper making dryer cylinders are large-diameter rotating cylinders that dry paper webs by conducting heat from steam through the cylinder wall. The cylinder surface is in continuous contact with the paper web, which creates a unique combination of wear and corrosion challenges:

• Abrasive wear: The paper web, containing cellulose fibres and additives, abrades the cylinder surface during continuous operation.
• Corrosive attack: The hot water and steam environment, combined with acidic or alkaline paper making chemicals, causes corrosion of the cylinder surface.
• Thermal fatigue: Repeated heating and cooling cycles cause thermal stresses that can lead to surface cracking and delamination.
• Surface roughness degradation: Over time, the smooth surface finish of the cylinder degrades, affecting paper quality.

Steam balls, or steam chests, are similar cylindrical components that distribute steam to the dryer cylinders. They are subject to similar corrosion and wear challenges but also experience internal pressure loading.

Repair Technology Description

The combined repair technology described in this paper involves two complementary processes:

Arc Surfacing Welding

The first step in the repair process is the application of a wear-resistant and corrosion-resistant surfacing layer to the cylinder surface using arc welding. The surfacing alloy is selected to provide:

• High hardness for wear resistance
• Good corrosion resistance in the paper making environment
• Adequate ductility to accommodate thermal cycling
• Good bonding strength to the base cylinder material

The surfacing welding process parameters are critical for achieving a sound, well-bonded layer:

Special Alloy Electroplating

The second step involves the application of a thin special alloy electroplating layer on top of the surfacing layer. This electroplating provides:

• A smooth, polished surface finish for high-quality paper production
• Additional corrosion protection
• Improved surface hardness and wear resistance
• A barrier against chemical attack from paper making additives

The electroplating process parameters are as follows:

Performance Results and Validation

The combined surfacing and electroplating repair technology was implemented at the Xinxiang No. 2 Paper Mill and validated over nearly five years of continuous operation. The reported performance improvements are summarized as follows:

The doubling of service life is a particularly significant result, as it directly translates to reduced downtime, lower replacement costs, and improved production continuity. The improvement in surface brightness is also important from a paper quality perspective, as surface defects on the cylinder can transfer to the paper web, causing quality issues.

Engineering Practice and Implementation Considerations

The implementation of this combined repair technology requires careful attention to several practical aspects:

1. Cylinder removal and handling: Large dryer cylinders must be carefully removed from the paper machine and transported to the repair facility. Proper handling procedures are essential to prevent damage to the cylinder surface.
2. Surface preparation: The existing damaged surface must be thoroughly removed by grinding or machining to expose sound base metal. The surface must be clean and free of contaminants before surfacing welding.
3. Welding distortion control: Surfacing welding on a large cylindrical component can introduce significant distortion. The welding sequence must be carefully planned to minimize warping. Symmetric welding patterns and controlled preheating are essential.
4. Post-weld machining: After surfacing welding, the surface must be machined to the required dimensional tolerances before electroplating. This step removes any surface irregularities from the welding process.
5. Electroplating uniformity: The electroplating must be uniform across the entire cylinder surface. This requires careful control of current distribution, particularly at the ends of the cylinder where current density tends to be higher.
6. Quality inspection: Both the surfacing layer and the electroplating layer must be inspected for defects, including porosity, cracking, and adhesion failures. Non-destructive testing methods such as magnetic particle inspection (MT) and eddy current testing (ECT) are appropriate for this purpose.

Study Insights and Reflections

This paper demonstrates the effectiveness of a combined surface engineering approach for repairing critical paper making equipment. The use of arc surfacing to provide a thick, wear-resistant base layer, followed by electroplating to provide a smooth, corrosion-resistant top layer, is a well-conceived strategy that leverages the complementary strengths of both technologies.

The five-year validation period provides strong evidence of the technology's reliability and durability. This is particularly important for surface engineering applications, where initial performance may not reflect long-term behaviour under cyclic loading and corrosive environments.

One aspect that I find particularly interesting is the use of special alloy electroplating as a finishing treatment over a surfacing weld layer. This approach is somewhat unconventional, as electroplating is typically applied to machined surfaces rather than weld deposits. The success of this approach suggests that the surfacing layer provides an adequate substrate for electroplating, with sufficient surface energy and chemical compatibility.

However, I would note that the paper does not provide detailed information on the specific alloy compositions used for both the surfacing and electroplating layers. This limits the ability to fully evaluate the metallurgical basis for the reported performance improvements. Future work should include detailed characterization of the layer compositions, microstructures, and bonding interfaces.

Reference Value and Outlook

This paper provides a valuable case study in the application of combined surface engineering technologies for industrial equipment repair. The methodology of using multiple surface treatment processes in sequence to achieve complementary performance benefits is directly applicable to other industrial applications, including pipe fitting repair, turbine blade refurbishment, and mining equipment maintenance.

The significant improvement in service life (more than doubled) provides a compelling economic argument for the adoption of this technology. For paper mills and other industries that rely on critical rotating equipment, the reduction in unplanned downtime and maintenance costs can be substantial.

The work by Liu Jifeng and Li Lin exemplifies the practical, applied research approach that has characterized Chinese surface engineering for decades. The combination of academic research with industrial validation provides a robust framework for technology development and deployment. As industries continue to seek ways to extend equipment life and reduce maintenance costs, combined surface engineering approaches like the one described in this paper will play an increasingly important role in asset management strategies.