LABORATORY IMPELLERS
Most of the styles found in both the Mixing and Dispersing sections are available in laboratory size. Some start as small as 1” while others will be 1.5” or 2.0” depending on the style. Laboratory impellers will attach to the shaft in several ways:
- Collar & Set Screw welded to the blade
- Collar & Set Screw affixed to the blade but removable
- Threaded shaft with nuts that screw down to tighten the blade
- Bore with a keyway and end cap
- Threaded bore in the bottom center of the shaft
- Special tapered end stud shaft for attaching with a collar and set screw
While the goal is always to make a formulation that can be duplicated in the plant, this can be challenging for mixing and dispersing. Most chemists prefer to match the tip speed of the blade in the lab with the tip speed of the blade in production. However, there are other factors which can contribute to scale up failure:
- The shaft rpm difference is huge. For example, on a dispersion blade will should travel at 5000 fpm, this translates as follows into rpm:
2” blade @ 5000 fpm = 9,555 rpm
20” blade @ 5000 fpm = 955 rpm - The distance from the tip of the blade to the sidewall of the tank is also huge. For example, most dispersion blades should be sized at 1/3 the tank diameter:
2” blade would be used in a 6” diameter tank leaving a space of 2” from the edge of the blade to the sidewall
20” blade would be used in a 60” diameter tank leaving a space of 20” from the edge of the blade to the sidewall - Temperature is difficult to duplicate in the lab vs the plant because of the huge difference in volumes and how the temperature will be transferred.
Still, having the ability to run lab trials with similar equipment and similar blades absolutely has a value and sheds light on how formulations and different types of additives will react in process.
For a quote or discussion, complete the IMPELLER BLADE SPECIFICATION FORM.
