Wheel Block System

The Demag DRS 250 is a high-performance chain hoist widely used in industrial production lines, warehouses, and maintenance workshops. As the core component of its travel mechanism, the wheel block's condition directly impacts the crane's smooth operation, safety, and the service life of both the runway and the structure itself. Timely and standardized replacement is crucial when wheels exhibit severe wear, cracking, or damage. This article systematically outlines the steps and key precautions for replacing the wheel block on the Demag DRS 250.

I. Preparation Before Replacement

• Safety First, Energy Isolation:

Move the DRS 250 crane to a spacious, solid area that does not interfere with other operations.

Perform comprehensive energy isolation: Disconnect the main power supply and attach a "Do Not Switch On" warning tag. This is the most critical step to prevent accidental startup.

Use reliable chocks to block the wheels and prevent the crane from moving during maintenance.

• Tools and Spare Parts Preparation:

New Wheel Block: Ensure the new wheel block is a genuine Demag or certified high-quality spare part, perfectly matching the DRS 250 model.

Common Tools: A set of wrenches, hex keys, screwdrivers, and a torque wrench.

Specialized Tools: Hydraulic jack, puller (for removing bearings or wheels with interference fits), brass hammer.

Auxiliary Materials: High-strength thread-locking adhesive, lubricating grease, cleaning cloths, rust penetrant.

• Personnel and Documentation:

Ensure operators are familiar with the DRS 250 structure and have read the equipment maintenance manual.

Have the equipment's technical drawings and repair manual ready for reference.

II. Wheel Block Replacement Steps

• Step 1: Removing the Old Wheel Block

Unload and Disconnect: Ensure the hoist is free of any load. Disconnect the motor power cables and control cables (if applicable) connected to the wheel block, marking them for reassembly.

Jack Up the Crane: Use a hydraulic jack to lift the crane near the main girder adjacent to the wheel block being replaced. Apply moderate force, lifting just enough to raise the wheel slightly off the runway. Avoid over-lifting, which can cause structural deformation or instability.

Remove Mounting Bolts: Locate the bolts securing the wheel block assembly. These bolts often withstand significant shear forces and may be very tight. Use appropriate wrenches, potentially with a cheater bar for leverage. Loosen them in a crisscross pattern and in stages to release stress.

Remove the Wheel Block: After all mounting bolts are removed, carefully withdraw the entire wheel block assembly from the end carriage or drive unit. If the block is stuck due to corrosion, gently tap around its mounting housing with a brass hammer. Never strike the axle or bearing directly with force.

• Step 2: Installing the New Wheel Block

Clean and Inspect: Thoroughly clean the wheel block mounting interface, removing all rust, burrs, and old sealant. Check that the mounting surface is flat and undamaged.

Position and Install: Align the new wheel block assembly with the mounting holes and slide it smoothly into place. Applying a small amount of anti-seize lubricant to the bolt threads beforehand can ease tightening and prevent future seizing.

Tighten Bolts: Hand-tighten all bolts first to ensure proper alignment. Then, using a torque wrench, tighten them evenly in a crisscross pattern, following the specified torque values from the repair manual, typically in two stages (e.g., first to 50%, then to 100% torque). This is the core step ensuring connection reliability.

Reconnect: Reconnect the motor and control cables, ensuring connections are secure and weatherproof.

• Step 3: Post-Installation Inspection and Testing

Lower the Jack: Slowly release the hydraulic jack, allowing the new wheels to rest steadily on the runway.

Initial Run Test: Without any load, manually push the crane or jog it at low speed to check for smooth rolling of the new wheels and any abnormal noise or binding.

Runway Gauge and Parallelism Check: Verify the gauge between wheels on both sides is within tolerance to prevent "rail gnawing."

Load Test: After all checks are complete, conduct a light load test, observing for stable operation. Only after confirming everything is correct should normal use be gradually resumed.

III. Key Precautions

Avoid Brutal Force: If disassembly is difficult, analyze the cause and use specialized tools instead of sledgehammers.

Torque is Critical: Always use a torque wrench and adhere to specified values. Overtightening can damage threads; undertightening can lead to loose bolts, causing serious incidents.

Replace in Pairs: To ensure consistent wheel diameters on both sides and prevent deviation, it is recommended to replace wheels on the same runway in pairs.

Root Cause Analysis: Abnormal wheel wear often has underlying causes, such as uneven runways, narrow rail heads, or drive misalignment. When replacing the wheel block, always check and address these potential issues; otherwise, the new wheels will wear out prematurely.

Conclusion

Replacing the wheel block on the Demag DRS 250 is a maintenance task that demands rigor and adherence to standards. By following standardized procedures, focusing on safety details, and using the correct tools and parts, you can not only effectively restore the equipment's performance but also fundamentally enhance the safety and service life of the entire crane system. If the necessary technical expertise is not available, be sure to contact a professional repair service team. Regular maintenance and professional replacement are the cornerstones of ensuring the long-term stable operation of your crane. Do not let minor wear on critical components lead to major safety risks. Upgrade your industrial operations with wheel block systems—where innovation meets reliability. Contact us to learn more!