During freeze drying and operation of a freeze dryer, some problems may raise. It either caused by misoperation or machine failures. In this post, Vikumer will list some frequency happened problems and the resolve methods. May you are using other brands freeze dry machines, but the solving ideas are similar.
1, Dried Product Shape Changed.
- If you are working with food items.
The dehydrated product shape changed, mostly because of the incompletely freezing of raws. The internal of raw product still wet, during freeze drying, huge pressure different between internal and external, will cause product popping.
Another reason maybe the lack of water sublimation channels. For example, blueberries that with hard skin, it is hard for water to come out during freeze drying. So, you have to broke its skin before freeze drying, the broken part will be vapor escape channels.
- If you are working with pharmaceutical, bio samples or chemicals.
Mainly you need check raw materials first. Concentration rate and ingredients for example. Quite a lot raw material needs dilute to a certain level can success lyophilization.
After that, the freezing curve and temperature check. Rapid freezing, slow freezing, annealing treatment or not etc. all will influence the final product shape, and drying time.
2, Product Cannot Dry.
Firstly, check if vacuum environment is created of drying chamber. Secondary, if condensing coils are chilled. Third, check if shelves temperature can raise normally. A commercial level freeze dryer, its controller screen should display all these information, you can see directly.
Once above information confirm ok, but problem still. The most possible problems are the sensors fail. For example, if your freeze dryer shelves cannot heat, but the heater and fluid pump is ok, definitely, the temp. sensor is broken. FYI: Sensor manufacturers always pre-program a broken temp. sensor show +100C or +1000C. So that even the sensor is fail, it will not pass wrong info to controller, which will cause continue heating and burn the raw materials.
3, Products are Carbonized
Because you set too high temperature during freeze drying. Vacuum freeze drying process takes quite long time. The heat energy supply should gradually, there are references when need raise shelves temp. Otherwise, too much heat in short time may melt the raw product and later cause product out of shape and burned.
4, Drying Chamber Pressure Cannot Pull Down to Set
To solve this problem, mainly to check 2 parts. 1 is the vacuum pumps, if its broken or oil need change. 2 is check if the door and valves not completely close.
For your information, vacuum pump oil present clear, transparent, if its milky, need replace immediately. Otherwise, it cannot create environment efficiently, and to itself, is not good.
5, Condenser temp. Abnormal
Compressor system cools the condenser directly by coolant expand. So, you need carefully check compressor system, of the H/L/M/O pressure, if normal or there is a coolant leakage.
6, Freeze Drying Recipe Cannot Automatically Execute
Freeze dryer has 2 working methods. Automatic and semi-automatic. Only in automatic condition, it can execute freeze drying steps automatically: one finish, another automatic start, until drying finish.
Above are the problems with freeze drying. Mainly for production scale freeze dryer machines. If you cannot find answers, please feel free to mail us, we are happy to answer and add above.