Suppose we have 127 kg material ready for blending and we have 2 size of blenders of capacity 200 kg and 500 kg, it is obvious we should take it in 200 kg but is there any guideline regarding that or just common sense to be applied .
Generally 75% to 80% capacity of blender should be used to get appropriate blending. If you use larger capacity of blender then there would be hammering action on granules thus granules will break to generate fine particles. If we use smaller capacity blender then mixing or blending will be inadequate due to less head space for movement of granules or powder to get blended.
AS per cGMP, you cannot change the blenders capacities without having the validation performed. Change in blender may result in improper mixing. The blender capacity is selected based on the occupancy. Generally the occupancy should be between 40 to 75%. Also the blender speed and the mixing time should be established.
Take the trail of each blending product to establish the blender rpm,mixing time and minimum and maximum quantity of blend product to be used.