Maintenance Guide and Technical Specifications for 20MG42.11.09 ZGM Coal Mill Grinding Roller Sleeve

The roller sleeve 20MG42.11.09 for Bowl-Type Medium-Speed Coal Mills is a core grinding component of the ZGM series. It bears the critical task of crushing and grinding raw coal. Its material properties, machining precision, and wear resistance directly determine the grinding efficiency, pulverized coal quality, and the overall equipment operation cycle.

As a primary consumable spare part during maintenance, this roller sleeve is manufactured from Cr2021 material through integral casting and CNC turning/milling. It must meet stringent hardness and surface quality requirements to ensure the stable operation of the mill.

1. Product Overview

The roller sleeve 20MG42.11.09 is specifically designed for ZGM series medium-speed mills. Installed on the exterior of the roller assembly, it works in coordination with the bowl liner. Through the pressure and shear forces generated by relative rotation, it grinds raw coal into qualified powder.

Manufactured using Cr2021 high-chromium alloy, the sleeve undergoes integral casting and precision machining. Following strict OEM standards, it must be free of embedded impurities or attachments, with a smooth surface devoid of penetrating cracks, grooves, or blowholes. It is precisely matched with auxiliary parts such as the shaft sleeve (20MG30.11.09.84), oil seal ring (300MG31.11.09.83), and oil seal bracket (20MG43.11.09.37), while withstanding the loading pressure from the hydraulic cylinder (25MG43.11.14).

2. Technical Features and Advantages

The 20MG42.11.09 roller sleeve offers three core advantages: superior wear resistance, structural reliability, and high compatibility.

• Material Performance: The Cr2021 alloy features high chromium content, providing excellent impact and corrosion resistance. The alloy layer reaches a Rockwell hardness of HRC55 (deviation $\leq \pm 2HRC$), extending service life by over 30% compared to standard materials.

• Precision Machining: The integral casting process avoids internal defects like sand holes. Precision milling ensures that the gap between the sleeve and the bowl liner is optimal, preventing vibration and efficiency loss.

• System Synergy: It is designed to work seamlessly with the sealing air pipe (ZGM113N) and the breather (20MG430011.09.01) to prevent coal dust from infiltrating the roller internals.

Core Technical Parameters

3. Application Scenarios

The 20MG42.11.09 roller sleeve is widely used in thermal power plants and large-scale coal chemical enterprises utilizing ZGM mills.

1. Routine Inspection: Every 1,000 operating hours, the surface must be checked. If the unilateral wear reaches 30% of the wall thickness, the sleeve should be flipped to ensure even wear and prevent vibration.

2. Overhaul (Mid/Major): During cycles of 8,000–12,000 hours, the roller assembly is disassembled. If penetrating cracks are found or the hardness exceeds the decay limit, the sleeve must be replaced.

3. Troubleshooting: If coal fineness decreases or equipment vibration increases, the roller sleeve is the first point of inspection. Issues in the hydraulic station (e.g., ZGM95N-II valve failure) can cause abnormal loading pressure, leading to localized over-wear of the sleeve.

4. Selection and Maintenance Recommendations

• Selection: Always verify the material report and hardness certificate. Ensure the dimensions match the specific ZGM model to maintain the correct grinding clearance.

• Maintenance:

  • Clean all interfaces before installation to remove oil and dust.

  • Use specialized tooling for positioning and control the assembly torque to ensure a tight fit with the shaft sleeve.

  • Regularly clear coal dust accumulation on the sleeve surface to reduce abrasive erosion.

  • Flip or replace the sleeve promptly based on wear measurements to extend the overall life of the grinding system.

HKZX-2026-01-30