Follow
Spray rate control is very important in aqueous film coating and if the spray rate varies during the coating process, several problems are encountered. The spray rate is controlled primarily through the use of a peristaltic pump. Peristaltic pumps are the simplest and easiest to clean. The spray rate can be controlled by the RPM of the pump. The spray rate also depends on the size of tubing used in the pump so depending on the desired spray rate, the appropriate tubing size should be selected.
The spray rate in a coating process can be easily monitored by placing the coating suspension on a balance to calculate the spray rate per minute. It is very important to monitor at least the first 3-5 batches and obtain the rpm of a peristaltic pump, which gives the required spray rate.
During film coating, pan load should be optimum or maximum. If the cover pan load is partial, a lot of inlet air can go directly to the exhaust duct and a lot of energy is wasted. Exhaust plenum is not fully covered due to partial load. This reduces the drying efficiency of the coating pan. Process ting with partial load is higher than with full load. The mixing efficiency of the coating pan also decreases with partial load and requires a higher pan rpm than is normally used. This is even more important in functional coatings such as enteric coatings where edge wear or damage may cause the product to fail disintegration tests.
To solve the problems associated with partial load, many machine manufacturers now use the multi pan method. Thus different drum sizes are provided to accommodate different batch sizes with a coating pan.
