Biological low-temperature refrigeration equipment (such as ultra-low temperature refrigerators, liquid nitrogen tanks, freeze dryers, etc.) is widely used in fields such as biological sample preservation and drug research and development. Its safe operation must strictly follow regulations to prevent equipment failure, sample damage, or personnel injury. The following are detailed safety operation methods:
1、 Preparation before operation
environment check
Ventilation requirements: The equipment should be placed in a well ventilated area, avoiding enclosed spaces (such as liquid nitrogen tanks to prevent nitrogen accumulation and suffocation).
Temperature and humidity: The ambient temperature should be between 10-30 ℃, humidity ≤ 80%, and kept away from heat sources (such as direct sunlight, heaters) and corrosive gases.
Ground flatness: The equipment should be placed on a stable and level surface to prevent tilting that may cause refrigerant leakage or mechanical failure.
Equipment inspection
Appearance inspection: Confirm that the equipment has no signs of damage, deformation, or leakage (such as abnormal frosting on the outer wall of the liquid nitrogen tank, which may indicate damage to the vacuum layer).
Power and grounding: Check if the power cord is intact and if the grounding wire is reliably connected to avoid the risk of leakage.
Accessory integrity: Ensure that accessories (such as temperature probes, liquid nitrogen tank neck plugs, freeze dryer cold traps) are complete and functioning properly.
personal protection
Protective equipment: Wear antifreeze gloves, goggles, and lab coats when operating liquid nitrogen tanks; Antifreeze tweezers and trays are required when handling ultra-low temperature samples.
Training requirements: Operators must undergo professional training, familiarize themselves with equipment principles, emergency procedures, and safety warning signs.
2、 Standardized operation
Temperature setting and monitoring
Set temperature: Set the target temperature according to the sample requirements (such as -80 ℃ for ultra-low temperature refrigerators) to avoid frequent adjustments that may cause compressor overload.
Real time monitoring: Continuously observe temperature changes through built-in display screens or external monitoring systems. Any abnormal fluctuations (such as ± 5 ℃ or above) should be immediately investigated.
Temperature recording: Regularly record temperature data (such as every 2 hours) and establish temperature logs for traceability.
Sample access operation
Quick access: The opening time of ultra-low temperature equipment should be controlled within 1 minute to reduce the loss of cooling capacity; When sampling liquid nitrogen tanks, a dedicated basket should be used to avoid direct contact with liquid nitrogen.
Layered storage: Samples are stored in layers by type and shelf life to avoid temperature fluctuations caused by frequent movement; Do not place heavy objects on top of the equipment.
Label management: Sample containers must be labeled with name, date, and temperature requirements to prevent misuse or expiration.
Special operation of liquid nitrogen tank
Filling specifications: The liquid nitrogen filling amount shall not exceed 80% of the tank volume to prevent excessive expansion pressure; Wear a protective face mask during filling to avoid liquid nitrogen splashing.
Neck plug usage: The neck plug of the liquid nitrogen tank should be kept in a semi open state (or a breathable neck plug should be used) to prevent nitrogen accumulation and pressure increase.
Liquid level monitoring: Check the liquid level weekly, and replenish it promptly when the liquid level is below 20% to avoid exposing the sample to room temperature.
Operation of freeze dryer
Pre freezing stage: The sample needs to be pre frozen to below -40 ℃ before being placed in a cold trap to prevent ice crystals from damaging the sample structure.
Vacuum control: When vacuuming, the valve should be slowly opened to avoid sudden pressure changes that may cause the glassware to break; Close the bypass valve after the vacuum degree stabilizes.
End processing: After drying is complete, release the vacuum first and then open the door to prevent the sample from absorbing moisture.
3、 Maintenance and upkeep
Daily cleaning
Internal cleaning: Clean the inner walls monthly with a neutral cleaner and avoid using corrosive solvents; The liquid nitrogen tank needs to be regularly cleaned of neck frost.
External cleaning: Keep the surface of the equipment dry to prevent water stains from seeping into the circuit system.
regular maintenance
Compressor inspection: Check the operation status of the compressor in the ultra-low temperature refrigerator every six months and clean the condenser dust (power off operation is required).
Vacuum layer testing: The liquid nitrogen tank undergoes annual vacuum degree testing, and if the vacuum value is below 10 ⁻ ² Pa, it needs to be returned to the factory for maintenance.
Sealing test: The sealing strip of the freeze dryer door needs to be checked regularly to prevent air leakage and affect drying efficiency.
Calibration and Verification
Temperature calibration: Every year, a professional organization is commissioned to calibrate the temperature sensor to ensure that the displayed value has an error of ≤± 1 ℃ compared to the actual value.
Performance verification: Verify the refrigeration performance of the equipment through standard samples (such as substances with known melting points) to ensure compliance with requirements.
4、 Emergency response
Temperature anomaly
Overtemperature alarm: Immediately check if the door seal is tight and if the sample is blocking the air duct; If the temperature continues to rise, transfer the sample to a backup device.
Low temperature alarm: Check if the refrigeration system is overloaded and adjust the set temperature appropriately (within the allowable range of the sample).
Liquid nitrogen leakage
Emergency evacuation: Quickly evacuate the leakage area and close the valve of the liquid nitrogen tank; If the leakage is large, start the ventilation system and report to the safety department.
Protective measures: When dealing with leaks, it is necessary to wear a self-contained breathing apparatus (SCBA) to avoid inhaling nitrogen gas and causing suffocation.
Equipment failure
Power off treatment: After the ultra-low temperature refrigerator is powered off, the door seal is sealed with tape to reduce the loss of cooling capacity; The liquid nitrogen tank needs to keep the neck plug partially open.
Professional maintenance: Non professionals are not allowed to disassemble the equipment. Contact the manufacturer or authorized repairer for troubleshooting.
5、 Safety Warning and Training
Warning sign
Warning signs such as "Low temperature danger", "Do not touch", and "Liquid nitrogen suffocation risk" should be posted on the surface of the equipment.
The storage area for liquid nitrogen tanks should be marked with "No Smoking" and "Good Ventilation" signs.
Training content
Including equipment principles, operating procedures, emergency plans, use of personal protective equipment, etc.
Regularly organize safety drills (such as liquid nitrogen leak simulation drills) to enhance emergency response capabilities.
6、 Compliance and Records
compliance requirements
Complies with the General Requirements for Laboratory Biosafety (GB19489) and the safety guidelines of equipment manufacturers.
The liquid nitrogen tank must comply with the standard of "Mobile Vacuum Insulated Cryogenic Pressure Vessels" (GB/T18442).
Records Management
Establish equipment usage records, including temperature logs, maintenance records, calibration certificates, etc., with a retention period of ≥ 5 years.