In 2011, S&L Group provided 12 sets of single screw conical mixers for Sumitomo Bakelite (Nantong) to mix phenolic resins Mixers with different size were offered according to the output demand of production process. Nantong factory is a wholly-owned company invested in China by Sumitomo Bakelite, which is the leading manufacturer of high-end PF resin in the world. PF resin is mainly used in the automotive industry. With the rapid development of Chinese automotive industry, the production capacity is not enough to meet the increasing orders. Since mixing is quite essential in the process, 24-hr running is a special requirement for this project. While at the beginning of 2014, S&L was invited to the production site for consultation about the upgrading solution of higher capacity.
The customer plans to enlarge the single screw mixer as big as possible in the limited space on site. After multi-directional field measurement and calculation, the maximum volume can be modified from 8000L to 12000L. Motor and gearbox, driving system and screw agitator should be adjusted accordingly. Due to the fixed steel structure on site, how to replace old mixer vessel body with a bigger one becomes difficult. After multiple studies and discussion on the premise of ensuring performance and use of the modified mixer, our engineers and users figured out solutions to all critical issues, though this is absolutely a great challenge.
Mixer Vessel Body
The mixer vessel body can be no longer dismounted there. Luckily, it is a flange connection design between top cover and mixer vessel body. We decided to extend the vessel body starting here with new flanged mixer vessel body. Since it is such a big flange with 2.8m diameter, directly flange connection way cannot make sure the good fitness between old and new vessel bodies. So internal welding is done on site where the old and new vessel bodies meet after positioning. This can ensure the integrity of the full mixer vessel body.
Driving system includes motor, gear reducer, distribution box, screw arm. Considering the over current mentioned by customer and the great resistance of materials itself, the complete driving system is upgraded with maximum safety factor. In this way, the driving system has bigger torque. Stronger screw arm downs the risk from shearing force and fatigue use.
For standard design if the screw is 4m long, bottom support below long screw is a must to make sure no bumping to vessel body and longer service life is expected. However, for this special industrial application, bottom support is absolutely not allowed. It is because resin gets clumps and hardens after frication with bottom support. With the counterbalanced screw arm, unbalance from long screw without bottom support can be decreased as much as possible.
Through months of efforts, S&L finally delivered the modified assembly at the end of September 2014. With professional training and instruction from S&L, installation, assembly and commissioning on site was done successfully in October. All jobs are done step by step.
Dismount the top cover, motor, reducer and agitator from the old mixer. After positioning, new flanged mixer vessel body temporarily fixed onto old body with bolts on the 2.8m diameter flange in the four-lug direction. Perfect welding and buffing are done inside of the vessel body to make sure integrity of the full mixer vessel body. So, the vessel body is ready.
Then we go to the installation for motor, reducer, screw arm and long screw. In this step, it is critical to get an ideal gap between vessel body and long screw, as we know vessel body is not made from one-piece steel plate. After installation for above parts, we turn motor fan manually and check necessary gap. Finally, the base plate for gear box is welded and fixed.
All installation done, 2-hour dry running test is a must. It is finally approved qualified, including aspects like temperature rise for motor and gear box, abnormal noise or not, allowable vibration or not and etc.
Modification Done Successfully
It has been about 7 years since the completion of the modification. At present, the equipment are running well, Sumitomo Bakelite is quite satisfied with the product quality and our technical ability. Meanwhile, S&L will cooperate with Sumitomo Bakelite to provide higher performance products and help the development of the chemical industry.