S&L's Innovative Mixer Retrofit: A Resounding Success Endorsed by Sumitomo Bakelite

Background

In 2011, S&L Group made a significant contribution to Sumitomo Bakelite (Nantong) by supplying 12 units of single screw conical mixers. These mixers were carefully selected and provided in various sizes to meet the specific output requirements of the production process for mixing phenolic resins. Sumitomo Bakelite's Nantong factory, a wholly-owned subsidiary in China, holds a leading position globally as a manufacturer of high-end PF resin, which is predominantly utilized in the automotive industry. As the Chinese automotive industry experienced rapid growth, the existing production capacity of the factory struggled to keep up with the surging number of orders. Given that the mixing process is of utmost importance, the project had a unique requirement of 24-hour continuous operation. Then, at the start of 2014, S&L was invited to the production site to consult on a solution for upgrading to a higher capacity.

Project Feasibility

The customer's objective was to maximize the size of the single screw mixer within the limited space available on-site. After conducting comprehensive field measurements and calculations from multiple angles, it was determined that the maximum volume of the mixer could be increased from 8000L to 12000L. This adjustment necessitated corresponding modifications to the motor, gearbox, driving system, and screw agitator. However, the presence of a fixed steel structure on-site posed a major challenge in replacing the old mixer vessel body with a larger one. Despite these difficulties, through numerous studies and discussions, S&L's engineers, in collaboration with the users, managed to find solutions to all the crucial issues, demonstrating their resilience and expertise.

Mixer Vessel Body

The situation with the mixer vessel body was complex as it could no longer be disassembled on-site. Fortunately, the top cover and the mixer vessel body were designed with a flange connection. The innovative solution was to extend the vessel body from this flange by adding a new flanged mixer vessel body. Due to the large diameter of the flange, which measured 2.8m, a direct flange connection would not guarantee a proper fit between the old and new vessel bodies. To address this, internal welding was carried out on-site after accurately positioning the old and new vessel bodies. This meticulous approach ensured the integrity of the entire mixer vessel body.

Driving System

The driving system of the mixer, which comprises the motor, gear reducer, distribution box, and screw arm, needed to be upgraded. Taking into account the customer's concerns about overcurrent and the inherent high resistance of the materials being mixed, the entire driving system was enhanced with the highest possible safety factor. This upgrade resulted in a driving system with greater torque. Additionally, a stronger screw arm was installed to reduce the risks associated with shearing force and fatigue during operation.

Bottom Support

In a standard design, for a screw with a length of 4m, a bottom support beneath the long screw is essential to prevent any contact with the vessel body and to ensure a longer service life. However, for this particular industrial application, a bottom support was not an option. This was because the resin would form clumps and harden upon friction with the bottom support. To mitigate the imbalance caused by the long screw without a bottom support, a counterbalanced screw arm was employed, which helped to minimize the associated issues as much as possible.

Installation

After months of dedicated effort, S&L successfully delivered the modified assembly in late September 2014. With the professional training and guidance provided by S&L, the on-site installation, assembly, and commissioning were completed successfully in October. The installation process was carried out in a systematic manner:

First, the top cover, motor, reducer, and agitator were removed from the old mixer. After proper positioning, the new flanged mixer vessel body was temporarily secured to the old body using bolts along the four-lug direction of the 2.8m diameter flange. Inside the vessel body, precise welding and buffing were performed to ensure the integrity of the entire structure, thus preparing the vessel body for further installation.

Next, the installation of the motor, reducer, screw arm, and long screw took place. A critical aspect of this step was to achieve an optimal gap between the vessel body and the long screw, considering that the vessel body was not made from a single piece of steel plate. After installing these components, the motor fan was manually rotated to check the required gap. Finally, the base plate for the gear box was welded and fixed in place.

Once all the installation work was completed, a mandatory 2-hour dry running test was conducted. The equipment passed the test with flying colors, meeting all the necessary criteria such as acceptable temperature rises for the motor and gear box, absence of abnormal noise, and within the allowable vibration limits.

It has been seven years since the completion of the modification, and the equipment is still operating smoothly. Sumitomo Bakelite is highly satisfied with both the quality of the product and S&L's technical capabilities. Looking ahead, S&L is committed to further collaborating with Sumitomo Bakelite to provide even higher-performance products and contribute to the continued development of the chemical industry.