FD alarms are integral to the freeze-drying process as they signal when something goes awry. These alarms are designed to notify operators of issues such as temperature deviations, pressure problems, and system failures. Understanding these alarms is crucial for maintaining product quality and ensuring the efficiency of the freeze-drying process.
Introduction
Freeze-drying, or lyophilization, is a critical process used in various industries, especially pharmaceuticals, to preserve perishable materials. One of the most common issues that operators face is the occurrence of FD alarms, particularly those related to failure temperatures during specific segments. These alarms can halt the process, leading to delays and potential product loss. In this article, we’ll explore the different types of FD alarms related to temperature failures, their causes, and the best practices for addressing these issues.
Freeze-drying alarm
Failure Temperature during Segment:Â
In the freeze-drying program, an admissible temperature deviation tolerance for monitoring the ramps has been pre-set. If the temperature value remains higher or lower than this admissible deviation for a longer time without interruption, a failure message is given.
The causes of this failure could be:
- The steepness of a preset ascending or descending segment was chosen to be higher than the maximum heating rate, cooling rate, or evacuation rate of which the freeze-dryer is capable.
- Due to failures in the cooling or heating system, the pre-set temperature cannot be maintained.
- Delay: Yes
- Auto Return: Yes
FD Alarm: Chamber pressure > Pmax:
This failure appears if the pressure rise in the system is higher than the pressure P-max set in the recipe. A failure message It appears that the oil in the vacuum pumps is dirty.
Dirty oil in vacuum pumps is a common culprit. Over time, the oil can become contaminated, reducing the efficiency of the vacuum pumps and causing a rise in chamber pressure.
If, at the beginning of primary drying, during the first evacuation, the pressure in the system does not fall below the set pressure plus P-max pressure value within the time set in the recipe,.
If, during PRIMARY and SECONDARY DRYING and UNLOADING TEMPERATURE, the pressure in the system rises above the set P-max pressure
The causes of this failure could be:
- The door seal is defective or
- There is a failure in the evacuating
- The condenser temperature is too high.
- One of the valves connected to the Freeze-Dryer is not
- There is water in the chamber or in the condenser.
- Delay the process. Yes (first evacuation) NO(during drying)
- Auto-return this process: Yes
FD Alarm: Failure Temperature at Segment end:
In the recipe for the freeze-drying program, an admissible temperature deviation for the corners of the temperature ramps has been pre-set.
If at the end of a segment, i.e., at a corner, the temperature deviation is higher than the admissible value, the program is stopped until the temperature is again within the admissible limits. In the last freezing segment, the set value must have been reached (+/- 0.5 °C).
If at the end of a temperature segment the temperature deviation remains higher than admissible for a longer time, a failure message is given.
The causes of this failure could be:
- The steepness of a preset ascending or descending segment was chosen to be higher than the maximum heating rate, cooling rate, or evacuation rate of which the freeze-dryer is capable.
- Due to failures in the cooling or heating system, the pre-set temperature cannot be maintained.
- Delay the alarm : Yes
- Auto Return: Yes
Process not started:Â Â
The operator started a process. The process didn’t start, and this failure message appeared. The causes of this failure could be: A pre condition for this process is not fulfilled
FD Alarm: Failure Condenser cooling
This failure message is given in the following case:
- The required minimum temperature in the condenser has not been reached within a certain pre-set time after the above-mentioned programs have been switched on.
The cause of this failure could be
- Failures in the condenser cooling
- Delay: Yes
- Auto Return: Yes
FD Alarm: Failure evacuation:
If, at the beginning of primary drying, during the first evacuation, the pressure in the system does not fall below the P-max pressure value within the time set in the recipe,.
The causes of this failure could be
- The door seal is defective or dirty.
- There is a failure in the evacuating
- The condenser temperature is too high.
- One of the valves connected to the Freeze-Dryer is not
- There is water in the chamber or in the condenser.
- Delay: Yes
- Auto Return: Yes
CIP Alarm: Pressure and Temperature Issues
Clean-in-Place (CIP) alarms are critical for maintaining the hygiene and efficiency of the freeze-drying equipment. Pressure and temperature-related CIP alarms indicate that the conditions within the system are outside the acceptable range.
CIP Alarm: Pressure CIP Water notO.K.:
This failure message appears when the pressure is smaller than the set point for 30. The cause of this failure could be:
- Failure in the CIP circuit system
- Failure of the pressure sensor
- Delay: Yes
- Auto Return: Yes
CIP Alarm: Temperature: CIP water is not OK.
This failure message appears when the temperature is not within the tolerance for 30. The cause of this failure could be:
- Failure in the CIP system
- Failure of the temperature sensor
- Delay: Yes and Auto Return: Yes
CIP Alarm: Conductivity and Timeout Issues
Conductivity and timeout alarms in the CIP system indicate potential issues with the cleaning media or flow rate. These alarms are vital for ensuring that the cleaning process is thorough and that no residues remain in the system.
CIP Alarm: Conductivity CIP media too low:
This failure message appears in the case of the conductivity being under the set point for 30, The cause of this failure could be:
- Failure in the CIP system
- Failure of the conductivity sensor
- Delay: Yes and Auto Return: Yes
CIP Alarm: Timeout CIP water inlet
This failure message is given in the following case:
- The unit remains longer than 1 minute in step ”water inlet.” The cause of this failure could be:
- Failure in the GIP circuit system
- Failure of the flow meter
- Delay: Yes
- Auto Return: Yes
Process step timeout
A process step timeout alarm indicates that the freeze-drying unit has remained in a particular step for longer than the pre-set time. This can occur due to various reasons, such as system inefficiencies or malfunctions.
This failure message is appear given in the case of the unit remains longer than the pre-set time in a sub-process step. There is a different hard-coded pre-set time for every sub-process step.
- Delay: Yes; Auto Return: Yes
Cool down rate of shelves too low:
Cooldown and heating rate failures occur when the system is unable to reach the desired temperature change within the expected time. This can impact the overall efficiency of the freeze-drying process and may lead to incomplete drying. This failure message is given during the unit test if the cool-down rate of the shelves is too low.
Check the cooling circuits of the individual cooling compressors that cool the heat transfer fluid.
- Delay: Yes; Auto Return: Yes
The cooling rate of the condenser is too low
This failure message is given during unit test if the cool-down rate of the condenser is too low.
- Check the cooling circuits of the individual cooling compressors that cool the condenser.
- This failure message is given during unit test if the pump-down rate of the unit is too low.
- for Windows PC, in manual mode (all other programs are off), check the ultimate pressure of the pumps
- by switching on vacuum pumps individually (by measuring point). Compare these values with the characteristic values of the pumps.
- Check the nitrogen gas flow
- Delay: Yes; Auto Return: Yes
heating rate of shelves is too low
Check the current input or the resistance of the individual heating groups to determine whether one or more heating rods are defective. Check the system for leaks.
- Check the door
- Check to see whether there is water in the condenser or in the
- If necessary, carry out leak detection at the freezer: check the flange connection, valve seats, etc.
- Delay: Yes; Auto Return: Yes
Heating shelves is not possible
This report is given when the difference between the set temperature value and the actual value is smaller than 1 oC. When this happens, the heating of the heat transfer fluid is omitted.
- Delay: No; Auto Return: Yes
Evacuation is not possible.
Evacuation failures occur when the system fails to reach the required pressure within a set time during the primary drying phase. This can be caused by defective door seals, high condenser temperatures, or issues with the valves connected to the freeze-dryer.
This message is given if the required temperature in the condenser cooling coils is not reached within the set time.
- Delay: No; Auto Return: Yes
leak test is not possible
This message appears if, in the plant test program, only the LEAK TEST. And the sub-program is switched on, and the required ultimate vacuum set as the starting point for the pressure rise measurements is not reached within the set time. Delay: Yes; Auto Return: Yes
Bellow leaky
This message appears if, during the step leak test, the pressure in the piston rod falls below the user-set minimum bellows pressure Maintenance work: Check the system for leaks. Delay: Yes; Auto Return: Yes
Conclusion
FD alarms play a crucial role in ensuring the safety and effectiveness of the freeze-drying process. By understanding the causes of these alarms and implementing best practices for maintenance and monitoring, operators can minimize disruptions and maintain high product quality. Regular system checks and prompt attention to any alarms can prevent minor issues from escalating into major problems, ensuring a smooth and efficient freeze-drying process.
FAQs of FD alarms in freeze-drying
What is the most common cause of FD alarms?
The most common cause of FD alarms is temperature deviations during the freeze-drying process, often due to incorrect settings or system malfunctions.
How can I prevent temperature-related FD alarms?
To prevent temperature-related FD alarms, ensure that the temperature ramps are set correctly. And regularly maintain the cooling and heating systems.
What should I do if a process fails to start?
If a process fails to start, check that all preconditions are met and review the system settings to ensure there are no errors.
How often should I check my freeze-drying equipment?
It’s recommended to check freeze-drying equipment regularly, at least before each major batch, to ensure that all systems are functioning properly.
What are the consequences of ignoring FD alarms?
Ignoring FD alarms can lead to process failures, compromised product quality, and potential damage to the freeze-drying equipment.