same blender, In initial batch blender occupancy is 35 to 45 %, in scale up batch size observed the blender occupancy is 65 to 70 % occupancy. shall be go with same tip speed calculation is = Pi * N* H or any changes need to do in the formula kindly confirm and explain how to correct it ?
In pharmaceutical tableting, the blender’s tip speed typically “does not need to be changed” when varying the weight of a blend within the same blender. Because the blender vessel size and diameter remain identical, operating at the same revolutions per minute (RPM) maintains a constant tip speed and delivers consistent shear force to the powder bed.
Although the tip speed/RPM remains the same, varying the fill weight (or load volume) directly impacts blending dynamics.
Optimal Fill Levels:- Blenders generally operate most efficiently when filled between 30% to 70% of their total working volume. If the blend weight is too low, the powder slides without cascading; if overfilled, there is not enough room for particles to diffuse.
Mixing Time:- While the ‘speed’ stays constant, the ‘duration’ of blending may need adjustment. A lower fill volume might require more revolutions (longer time) to achieve the same degree of homogeneity as compared to a fuller batch.
Particle Segregation:- Underfilling or overfilling a bin can alter flow dynamics, sometimes resulting in the segregation of active pharmaceutical ingredients (APIs) or excipients with varying particle sizes and densities.
Yes, I agree what you said but how to calculate the mixing duration, if the blending occupancy below 30 %
Generally, blending occupancy below 30% of its working capacity is not acceptable. Therefore, it is not advisable to use less than 30% of the blender’s working volume.
Even if we use 30-70% of the blender’s capacity, it is necessary to optimize the blending process to determine the blending duration to achieve blend uniformity. This should be followed by validation of the blending process by repeating the blending operation 3 times (generally) with the same conditions and statistically deriving the blend’s content uniformity by sampling from different positions of the material mixed in the blender and analysing those samples for that analyte.
Thank you for response.
What is the value of travelling time and RPM, how to match with 30% occupancy and 50 to 60% occupancy.
Is there any tip speed calculation formula ?
Other than which I mentioned formula.