chapter  7
12 Pages


Freeze dryers are pieces of equipment that are designed to operate un­ der negative pressure during normal product processing. Pressures that are encountered in the freeze drying process may be in the region between 1 and 0.001 mbar. With atmospheric pressure acting on the outside of the plant, any leaks into the freeze dryer during this time will cause control of the cycle to be compromised. It is impossible to make this type of equipment completely leaktight; therefore, the prob­ lem of air leakage into the freeze dryer must be accepted as a process hazard. The degree of leakage will have consequences on the contents of the plant; therefore, the leak rate should be measured, with any likely effect on the final product being assessed.