German Steel Mill Successfully Replaces Rexroth Large Hydraulic Cylinders, Achieving 100% Interchangeability and Reducing Costs by 40%
An equipment maintenance company that has long served a major German steel manufacturer needed to replace a large Bosch Rexroth hydraulic cylinder in the rolling mill’s hydraulic system.
The rolling mill had been in continuous operation for over 15 years, and the original hydraulic cylinder was an early Rexroth model. As production of the original model was gradually phased out, the customer faced issues such as rising procurement costs, excessively long lead times, and an unstable supply of spare parts.
Based on the original hydraulic cylinder drawings, on-site measurements, and installation interface data, GY Hydraulic recreated a 3D model and completed a 1:1 replacement design.
Ultimately, the new hydraulic cylinder could be installed directly without any modifications to the equipment structure, achieving 100% interchangeability. Procurement costs were reduced by approximately 40%, and the delivery lead time was shortened from 16 weeks to about 4–5 weeks.
Customer Requirements and Project Objectives
The customer sought a replacement solution for large hydraulic cylinders that would ensure a long-term, stable supply while retaining the existing rolling mill structure and hydraulic system.
This project not only required the new hydraulic cylinders to operate normally but also demanded that all critical mounting dimensions match those of the original Rexroth hydraulic cylinders.
The customer’s primary project objectives included:
* No modifications to the rolling mill equipment structure
* 100% interchangeable installation
* Maintain the original hydraulic system interfaces
* Shorten the hydraulic cylinder procurement cycle
* Reduce spare parts procurement costs
* Meet the steel mill’s heavy-duty operating requirements
* Establish a long-term, stable supply channel for spare parts
For the customer, simply using a similar model would not solve the problem. Only by achieving true “plug-and-play” functionality can equipment modifications, installation rework, and additional downtime be avoided.
Customer’s Detailed Technical Requirements
1. Must Match the Original Mounting Flange Exactly
The flange dimensions, mounting hole locations, and connection methods of the new hydraulic cylinder must match those of the original Rexroth hydraulic cylinder.
If there are deviations in the flange dimensions, the customer will need to re-machine the mounting location, increasing equipment retrofit costs and installation risks.
2. The Mounting Center Distance Must Remain the Same
The connection points at both ends of the hydraulic cylinder and the mounting center distance must remain unchanged.
This ensures that the hydraulic cylinder will properly interface with the rolling mill’s existing mechanical structure after installation.
3. Port Locations Must Remain Consistent
The orientation, location, and connection interfaces of the new hydraulic cylinder’s ports must match those of the original hydraulic system.
This allows customers to continue using the existing hydraulic piping without having to reroute the lines.
4. Stroke and Overall Length Must Be Identical
The stroke of the hydraulic cylinder directly affects the operating range of the rolling mill’s actuators.
The new hydraulic cylinders must maintain the same stroke, closed length, and overall installation length to avoid affecting equipment operation.
5. Must Be Suitable for Heavy-Duty Conditions in Steel Mills
Rolling mill hydraulic cylinders are subjected to high loads, impacts, and continuous operating pressure over extended periods.
Therefore, the new hydraulic cylinders must not only match the dimensions but also feature reliable sealing, wear resistance, and corrosion resistance.
Key Challenges Faced by Customers
- Since the original hydraulic cylinders are a special model, the manufacturer’s purchase price is approximately 30%–50% higher than that of similar products on the market.
- Some of the Rexroth hydraulic cylinders used by the customer belong to an earlier product series.
- The manufacturer’s lead time exceeds 16 weeks.
- There is uncertainty regarding the future supply of spare parts.
GY Hydraulics Engineering Solutions
In response to the customer’s specific needs, Guoyue Hydraulics did not simply replicate the original product’s external design.
The engineering team employed reverse engineering methods to measure, model, verify interfaces, and optimize the structure of the original hydraulic cylinder, thereby enhancing the cylinder’s adaptability to steel mill operating conditions while maintaining the same installation dimensions.
- Based on the original hydraulic cylinder drawings provided by the customer, on-site measurements, and equipment installation interface data, a complete 3D model was rebuilt.
- All critical dimensions affecting equipment installation were matched to those of the original Rexroth hydraulic cylinder.
- Upgrading the Hydraulic Cylinder Sealing System
- To address the heavy-duty operating environment of steel mill rolling mills, the engineering team optimized the materials used for the hydraulic cylinder’s key components.
| Project Item | Recommended Solution |
|---|---|
| Application Equipment | Steel mill rolling mill hydraulic system |
| Original Cylinder Brand | Bosch Rexroth |
| Replacement Product | Custom-engineered heavy-duty hydraulic cylinder |
| Engineering Method | Reverse engineering, dimensional verification and 3D modeling |
| Replacement Type | 1:1 drop-in replacement |
| Installation Compatibility | 100% interchangeable installation |
| Mounting Flange | Matched to the dimensions and bolt pattern of the original cylinder |
| Piston Rod Connection | Matched to the original connection dimensions |
| Hydraulic Port Position | Maintained in the same position as the original hydraulic system interface |
| Mounting Center Distance | Matched to the existing rolling mill structure |
| Overall Length and Stroke | Produced according to the original cylinder specifications |
| Seal Options | Trelleborg, Parker or Hallite seals, depending on project requirements |
| Material Optimization | Upgraded piston rod and cylinder tube materials for improved wear and corrosion resistance |
| Surface Treatment | High-hardness chrome plating for improved piston rod durability |
| Quality Inspection | Pressure testing, internal leakage testing, dimensional inspection, coaxiality inspection and final performance testing |
| Equipment Modification | No equipment modification required |
| Original Lead Time | Approximately 16 weeks or longer |
| Replacement Lead Time | Approximately 4–5 weeks |
| Lead Time Reduction | Approximately 70% |
| Cost Reduction | Approximately 40% compared with the original OEM solution |
| Primary Project Benefits | Lower procurement cost, shorter downtime, direct installation and reliable long-term spare-parts supply |
Project Implementation Results
After the hydraulic cylinders were delivered to the customer, they were successfully installed on-site and put into operation on the first attempt.
The entire installation process did not require any modifications to the existing equipment structure, mounting brackets, or hydraulic piping.
| Comparison Item | Original OEM Solution | Guoyue Hydraulic Solution |
|---|---|---|
| Product Brand | Bosch Rexroth | Guoyue Hydraulic Custom Replacement |
| Installation Compatibility | Original OEM Fit | 100% Interchangeable |
| Equipment Modification | No Modification Required | No Modification Required |
| Procurement Cost | Original OEM Price as 100% | Approximately 40% Lower |
| Lead Time | Approximately 16 Weeks or Longer | Approximately 4–5 Weeks |
| Lead Time Reduction | — | Approximately 70% |
| Spare Parts Supply | Supply Risk for Discontinued Models | Long-Term Supply Solution Available |
| Maintenance Cost | Relatively High | Significantly Reduced |
| Installation Result | Original OEM Installation | Successfully Installed and Commissioned on the First Attempt |
Benefits Realized by the Customer
- 100% Interchangeable Installation
- Procurement costs reduced by approximately 40%
- Lead time shortened from approximately 16 weeks to approximately 4–5 weeks, representing a reduction of about 70%.
- Secured a long-term, stable supply of spare parts
- Reduced equipment downtime and maintenance burden
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