Sizing and Design of Equipment

The range of applications of size reduction is very wide. It includes the preliminary breakup of large masses into pieces that can be handled in a process and the grinding of smaller particles into fine powders. The size and design of equipment reflect this situation. Broadly, size reduction apparatus can be divided into those types which depend on mechanical crushing and those which use impact to fracture the solids. Table 3-13 shows some of the common types of equipment with their principal characteristics. Major hazards are those associated with the machinery and with the material being processed. 

These matters are organized into three major divisions the types of equipment, the criteria employed in the selection of equipment, and the sizing and design of the equipment. 

In order to develop a reproducible manufacturing process, attention must be given to particular instructions and screening procedures. For instance, excipients should be free of lumps and proper screening will aid raw material dispersion. Additionally, one should specify the size and design of containers and all equipment to be used. 

The functional relationship between product temperature, on the one hand, and shelf temperature and chamber pressure, on the other hand, is affected by many factors including the size and design of the lyophilizer, the characteristics of the product, and the time evolved since the start of primary drying. With a sucrose formulation in vials, we have observed a maximum primary drying product temperature rise of -i-5°C when the shelf temperature was varied from -15 to -i-30°C, whereas a pressure variation from 30 to 250 microbars generated an increase of around -i-2.5°C. With a lactose formulation in ampoules lyophilized in a larger freeze-dryer equipped with a plate-type condenser, the effect of pressure was found to be predominant -i-6.5°C for a pressure move from 50 to 300 microbars, versus -t-l°C for a shelf temperature move from 0° to 25°C. 

In some countries the ambient temperature can vary significantly over a 24-hour period, and its average daily value can also vary widely over a 12-month period. The power plant designer should therefore ascertain the minimum and maximum ambient temperatures that apply to the plant. The maximum value will be used frequently in the sizing and specification of equipment. The minimum value will seldom be used, but it is very important when the sizing of generators and their prime movers are being examined. 

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