Liquid nitrogen becomes dangerous if handling and storage are not performed properly. We have to follow some special procedures for this purpose.
Liquid nitrogen, which is also known as LN2, is a colorless, odorless, and tasteless liquid. Unlike most chemical solvents and materials used in industry, LN2 has no warning properties. This means that special care is required for storage and handling when you are working with this liquid. It is extremely cold and has other important properties like no flammability and no corrosiveness.
If proper storage and handling procedures are not followed, LN2 can cause several hazards.
- The vaporization of LN2 to nitrogen gas may cause over-pressurization and explosion. This expansion ration is 700x in unvented containers and equipment.
- You may get burned due to the exposure to the cold temperatures.
- It may displace the oxygen of the work area and may cause asphyxiation.
Use of personal protective equipment is essential for liqui d nitrogen handling and storage. This includes:
Gloves - You should use gloves that are waterproof and thermally insulated to protect your hands from burning. Bear in mind that these gloves are not made for submerging in liquid nitrogen. Therefore, you have to remove the gloves quickly if nitrogen gas is spilled on them.
Goggles - Use of chemical splashed goggles is very important when handling liquid nitrogen. The eyes are very sensitive toward LN2 vapor and can be injured in the event of an over-pressurization that causes an explosion of improperly vented equipment.
Body Equipment - You should also use lab coats or thermal insulated aprons and closed toe shoes to protect your body from danger.
Basic training is required to handle and store liquid nitrogen. You must have completed EOHSS or WHMIS training before entering the work area.
Handling and Storage Procedures
- Liquid nitrogen must be stored only in areas where ventilation is possible; never store the tanks in a confined area. The best container to store it in is a cryogenic container. This is because it contains pressure relief devices to control internal pressure of the liquid. It would be dangerous if you plug, remove, or tamper with these pressure relief devices.
- You should keep in mind that any unprotected part of the body should not come in contact with uninsulated equipment that contains liquid nitrogen. This is because the extremely cold metal can stick quickly to flesh tissues and if someone tries to help the victim withdraw, severe skin tearing may occur.
- Use a hand truck for all movement of the containers. The containers must be stored in upright position. You should not drop, tip, or roll the containers while moving them one place to another.
- Use proper equipment that can withstand the pressures. You can use check valves or other protective apparatus on gas withdrawal systems in piping from the container to avoid reverse flow.
- You must use pressure relief devices in the piping so as to prevent the liquid nitrogen from being trapped in between valves.
- Transfer line piping that is specially designed for cryogenic liquids should be used with the containers. This is because lines made up of common metal alloys like carbon steel may crack at very low temperature.
- Self-Contained Breathing Apparatus (SCBA) must be present at the work place. If a worker is suffering from lack of oxygen, take him to fresh air. If the breathing is difficult, use the SCBA to prevent asphyxiation.
If your skin comes in contact with the liquid nitrogen, remove the cloths that may restrict the circulation of the frozen area. Don’t rub the area, it may increase the damage. Now, you should place the affected part in warm water having temperature below 400C. Don’t use dry heat to warm the affected area.
- If eyes are exposed to the liquid nitrogen or its vapor, immediately wash them by warm water of the same temperature.
- Frozen tissue is painless and seems waxy with a yellow color. When it becomes thawed, it becomes painful. If thawing takes place, cover the area with a dry sterile dressing using a large protective covering.
- Call the physician immediately for treatment.
Liquid nitrogen storage should only be done by experienced and trained workers. Following the precautions is very necessary to avoid accidents. Nowadays, better technologies, such as nitrogen blanketing, are being used in containers to reduce the chances of explosion or eruption. This blanketing system creates an inert atmosphere inside the tank to reduce the risk of fire. It also increases the operational efficiency of the container. It keeps moist air out so corrosion can’t take place inside the container.