Froilabo BM 3E Essential, Руководство пользователя

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Original manual – Iss. 0.1 User manual – BM 3E Freezer 43/ 44
13.2 Liquid nitrogen backup
Strict rules must be followed when handling cryogenic fluids such as liquid nitrogen. These rules are intended to avert
two key risks:
anoxia and burns from contact or splashes. Air contains 21% oxygen and 78% nitrogen, by volume. At
atmospheric pressure, liquid nitrogen evaporates at temperatures greater than –196°C.
In a cryogenic room, natural evaporation from recipients, filling, and handling of stored samples result in continuous
evaporation of liquid nitrogen. This can increase significantly if a fault occurs. If the room is not sufficiently well
ventilated, the nitrogen gas generated can cause the atmosphere to be depleted in oxygen.
Properties of nitrogen liquid
Does not sustain life or combustion.
Present in air (78%).
The evaporation of one litre of liquid nitrogen generates 680 litres of gas.
Heavier than air at low temperatures.
Non-flammable and colourless.
Ensuing risks:
Risk of asphyxiation and loss of consciousness. An atmosphere with less than 16% oxygen is hazardous (nitrogen gas
displaces oxygen in the air).
Nitrogen gas builds up in low areas.
Risk of frostbite.
Risk of corrosion of steels in the presence of humidity.
In closed vessels, the pressure can reach very high values (in the order of 700 bar) resulting in a risk of bursting.
Essential precautions to be taken
Areas where liquid nitrogen is stored or used must be well ventilated (extraction or ventilation at both high and low
levels in the room).
Areas liable to contain an unbreathable atmosphere must be indicated with an asphyxiation hazard pictogram.
Never enter a room that has contained liquid nitrogen without taking predefined precautionary measures.
Eliminate links between areas where liquid nitrogen is stored or used and low points (pits, drainage channels,
basements) where it could accumulate and render the atmosphere unbreathable.
Use an O
2
concentration detector to ensure that the oxygen concentration is greater than 18%.
Avoid uninsulated liquid nitrogen pipes in any areas.
Call on the services of a specialist to determine the layout of facilities.
In the event of an incident or accident
If asphyxiation has occurred
Check the oxygen concentration in the room and then take the victim to the open air (taking an insufflator with you).
Begin artificial respiration and call the emergency services.
In the event of a leak
Evacuate the room.
Do not enter the room without breathing apparatus if the oxygen concentration is lower than 18%.
Close the valve on the leaking circuit.
Air the room at length, ensuring that low points are ventilated.
If liquid nitrogen is splashed:
In the eyes: Rinse the eye thoroughly for at least 20 minutes. Call a doctor.
On the skin: Do not rub. Remove clothing if necessary. Warm up the affected areas as quickly as possible under
running water for 20 minutes. Call a doctor.
PRECAUTIONS WITH REGARD TO EQUIPMENT
Warning: Nitrogen is liquid at extremely low temperatures and is stored in a double-walled tank. A high vacuum
between the walls ensures good thermal insulation. This equipment, especially mobile storage tanks, must be handled
with care.
Avoid impacts. Never lay a cryogenic container on its side.
Do not expose containers to excessive temperatures.
Treat valves with care (operate gently, do not dismantle or lubricate valves).
All equipment used must be in good condition and designed for use at the intended temperature and pressure.
Mobile equipment must be sheltered from inclement weather. Open-necked containers must be fitted with stoppers
to avoid the neck becoming blocked by cryopumping of ambient humidity.
Use suitable connection hoses; never use intermediate couplings.
Monitor the pressure of closed containers and check safety equipment (pressure relief valve).
Regulations apply to the transportation of recipients.
Users of the equipment, who are fully aware of the conditions of use and thus best placed to monitor the equipment,
are solely responsible for proper use.