Overlay Repair of Phi 1000 x 260 Roller Press Squeeze Rollers

Literature Overview

The technical case report by Wei Jianjun, Huang Zhiquan, Pan Jian, Xu Jian, and Huang Shilin, published in Cement (1995, Issue 8, p. 15), documents the overlay welding repair of a Phi 1000 x 260 roller press squeeze roller at a bulk cement company in Shantou, Guangdong Province. The roller press, used for cement grinding, had experienced severe wear on its static roller after approximately one year of continuous service. The study reports on the repair approach, overlay welding procedure, and post-repair performance, providing a practical case study in heavy equipment surface engineering.

Technical Background and Challenge

Roller presses are critical equipment in cement grinding circuits, where two large rollers rotate against each other to crush clinker and raw materials. The squeeze rollers are subjected to extreme combined loading: high contact pressure (exceeding 100 MPa), abrasive wear from cement particles, and cyclic thermal loading from the hot grinding process. The static roller, which remains stationary while the pressure roller rotates, is particularly susceptible to wear because it cannot benefit from the self-cleaning effect of rotation.

The following table summarizes the equipment and repair parameters:

Repair Procedure and Process Control

The repair procedure involved several critical steps that must be carefully controlled to ensure a durable repair. First, the worn surface was prepared by grinding to remove all loose, oxidized, and contaminated material, exposing clean base metal. The surface was then roughened to provide mechanical keying for the overlay weld metal.

The overlay welding was performed using a hard-facing alloy designed to withstand the abrasive and impact loading conditions of cement grinding. The selection of overlay material must consider several factors: hardness level (typically 45-55 HRC for cement applications), toughness to resist impact from clinker chunks, and compatibility with the base roller steel to prevent cracking.

The welding sequence for a large roller surface requires careful planning to minimize residual stress and distortion. A systematic approach should be used:

1. Divide the roller surface into welding zones, typically in a spiral or segmental pattern.
2. Weld each zone with multiple passes, alternating between opposite sides of the roller to balance thermal input.
3. Control interpass temperature to prevent overheating of the base metal.
4. Apply post-weld stress relief heat treatment if the residual stress is expected to exceed acceptable limits.

Engineering Practice Analysis

The success of this repair case demonstrates the economic and operational value of overlay welding for heavy equipment maintenance. Replacing a worn roller press squeeze roller would involve significant cost for new material, machining, and installation, as well as production downtime. Overlay welding repair allows the roller to be restored to functional condition with minimal downtime and at a fraction of the replacement cost.

The following quality control measures should be implemented for such repairs:

• Visual inspection of the prepared surface for cracks, porosity, and contamination.
• Hardness testing of the overlay surface after welding and grinding to verify the required hardness level.
• Ultrasonic testing (UT) of the overlay-base metal interface to detect lack of fusion or cracking.
• Dimensional verification after grinding to ensure the roller geometry meets operational specifications.
• Trial operation with monitoring of wear rate to validate the repair effectiveness.

Key Questions and Reflections

This case report, while practical and valuable, lacks detailed metallurgical analysis and quantitative performance data. The article does not specify the exact overlay alloy composition, welding parameters, or the measured hardness and wear resistance of the repaired surface. From a modern engineering perspective, a comprehensive repair report should include:

1. Detailed specification of the overlay consumable, including chemical composition and mechanical properties.
2. Welding parameters (current, voltage, travel speed, wire feed rate) for each pass.
3. Preheat and interpass temperature records.
4. Post-weld heat treatment parameters.
5. Non-destructive testing results (UT, MT, PT).
6. Hardness profile measurements across the overlay depth.
7. Service life data comparing the repaired roller with the original roller.

The absence of this data limits the transferability of the experience to similar repair situations. Engineers should use this case as a starting point for developing more rigorous repair procedures with comprehensive documentation and quality assurance protocols.

Study Insights and Implications

This case report illustrates the fundamental value of overlay welding as a maintenance technology for heavy industrial equipment. The successful repair of a large roller press squeeze roller demonstrates that well-executed overlay welding can extend the service life of critical equipment components, reducing capital expenditure and production downtime. For engineers involved in equipment maintenance and surface engineering, this case reinforces the importance of systematic repair procedures, proper consumable selection, and thorough quality verification. The economic benefits of repair over replacement are compelling, and the technical feasibility is well-established. Modern engineers should build upon the lessons of this case by developing standardized repair procedures with detailed process specifications, quality control requirements, and performance tracking to ensure consistent and reliable repair outcomes across their operations.