Product Spotlight


Biggest Slurry Tank in the World? Gigantic Technology Challenge


by VA Technology


being able to cast the largest finished item as a single piece are immense– not only in weight reduction, which is of critical importance to aerospace, but in every engineering sector, where the avoidance of major part sub-assembly enables greater flexibility in design, shape, aesthetic form, and ultimately in delivered cost. So when VA Technology took on of engineering a system


A the challenge


capable of producing the ‘Largest Ceramic Shells in the World’, the requirement for slurry tanks capable of coating shells of 2.5M (8.2 ft) in diameter was just one of the ground- breaking hurdles to overcome. To achieve the shell coating required


characteristic and to work


within the end user building structural limitations, the basic requirement for the slurry tank translated to: Rotating Tank Diameter: 3.3M. (129in.) Rotating Depth: Weight of Slurry:


1.8M ( 72in.) 20 tons


For slurry mixing, the important task


With the engineering team's experience of having delivered a large number of slurry tanks over a 25 year plus period, the team had a wealth of technical data to call upon to ensure that the key operational requirements could be achieved.


Principal areas for focused attention were identified as: 1. Slurry Mixing 2. Bearing Arrangement Design 3. Minimum heat input 4. Power Transmission 5. Mechanical Structure 6. Control Arrangement 7. Machine Monitoring 8. Serviceability 9. Testing 10. Transportation to site


26 ❘ January 2018 ®


was to try to emulate the characteristics achieved in industry standard sized slurry tanks.


The team recognized The standard size of


1200mm (48 inch) diameter was taken as the benchmark, and rotational speeds for ceramic slurry of similar formulation were assessed.


that if the same peripheral velocities were applied to the Large Project (LP) tank, then the ‘mean flow velocities’ at the 1200mm range would be too low.


Similarly, applying excessively


high velocities to the LP tank would cause a new range of problems. ie, centrifugal flow reversion, low annular interspersion, and high frictional losses due to mix vectoring. Previous flow testing trials with standard sized tanks were reviewed.


Tanks were filled with water, and emulsified color injected to determine mix flow paths and also to determine the time taken for the liquid to intersperse throughout the tank, identified as Time to Opacity (TTO). Simultaneously, mathematical simulations were undertaken to establish the optimized solutions. Finally,


a four vertical blade


arrangement with a dual horizontal plow blade was selected as the best design for the task. Each of the vertical blades were sized proportional to the tank diameter, and engineered to facilitate the independent adjustment of the blade vector angle. The design also enable the blade to be adjusted horizontally, increasing or decreasing the gap between the blade


dvances in process technology have enabled product designers to think bigger. The benefits of


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