Protocol for handling liquid nitrogen tanks

Introduction

The following protocol describes how to safely transport and fill liquid nitrogen in 150- 250 L cryogenic containers on wheels.

Safety info

Protect hands with cryo gloves, long sleeve shirts, wear protection glasses and put on closed shoes (not boots where liquid can splash and trapped into) when filling liquid nitrogen from the basement. Liquid nitrogen is an extremely cold material, also in a gaseous state. The vapor of liquid nitrogen can rapidly freeze skin tissue and eye fluid, resulting in cold burns, frostbite, and permanent eye damage even by brief exposure. Cold objects may also stick to the skin and tear the flesh when you attempt to free yourself. Nitrogen gas is colorless, odorless and tasteless. It can therefore not be detected by the human senses and will be breathed as if it were air. Breathing an atmosphere that contains less than 19 percent oxygen can cause dizziness and quickly result in unconsciousness and death.

In the event of spillage of liquid nitrogen on a person

If exposed to liquid or cold gas, restore tissue to normal body temperature, 37°C, followed by protection of the injured tissue from further damage and infection. Remove or loosen clothing that may constrict blood circulation to the frozen area. Rapid warming of the affected part is best achieved by using water at 42°C. Water should under no circumstances be over 44°C, nor should the frozen part be rubbed either before or after rewarming. If a person seems to become dizzy or loses consciousness while working with liquid nitrogen, move the person to a well-ventilated area immediately. If breathing has stopped, apply artificial respiration. If breathing is difficult, give oxygen. If in doubt contact Legevakt (phone 116 117 or 113 for emergencies).

If someone get liquid nitrogen it in the eyes, call 113, wash the eyes with appropriate equipment immediately.

Safety valves defects

Leave the room and place "do not enter" sign on doors if the safety valves are continuously releasing pressure. The pressure in the tank should decrease within time if the release valve is working fine. The signs can be found in the safety cabinet.

In events of frozen/broken LN2 container valve (on the wall) for filling LN2 in the basement

Close the "main valve" (labeled and marked with a green arrow) placed back on the LN2 container next to the back door.

Transporting tanks

To take the tank to the basement and back up to the 5^th floor:

• Transport one tank at a time.
• Place the tank into the lift with the "suffocation" chain sign blocking the elevator door opening (hangs on the rack in the corridor on 5th floor ) and the "no-one should enter the lift" sign on the tanks towards the door, push the basement button and exit the lift. Make sure the sign is clearly visible from the door. The tank will leak over time, and there is a risk of suffocation if the lift get stuck and someone is inside with the tank.
• Place the metal bridge over the door step so the tank can be taken in and out of the LN₂ container room in the basement smoothly.
• When full tanks are sent in the elevator it is recommended to be two people as far as possible, so one can wait at the end floor when the elevator comes. This is to prevent the elevator to move to another floor before the tank is taken out. No one must take the elevator with cryo tanks.
• As far as possible be two people when transporting a tank through a door opening that does not have a door opener. Alternative move the tank through a door by entering rooms backwards
• Tanks that are not in use (full or not) are stored in the gas room or instrument room, as these rooms are well ventilated.

Filling is mainly performed by a trained person in the LN₂ container room in the Realfagsbygget building basement. Use the metal bridge over the door step to prevent the tank from tipping. Remember to fill out your name, project no, signature, liter of liquid nitrogen used in the red ”geovitenskap” binder. Full tanks should be taken to the gas storage room or in an instrument room at the 5th floor as soon as possible after filling.

Current instructions (for filling yourself):

Equipment: Wrenches (size 19mm and 22mm), cryo gloves, ear protection, face shield, room key (hangs on the rack in the corridor on 5th floor ).

1. Attach the right-side ”trykk-fylling” tubing on the wall to the yellow valve on the cryo. It is important to choose right tubing since the tubing must be connected to a release valve.
2. Use both wrenches to slightly tighten the tubing. Make sure to straiting up the tubing before you fasten it.
3. Open the back door to improve the ventilation of the room.
4. Check the pressure of the big LN2 container to predict how long the filling will take. The Pressure display is located at the back of the container. Full tanks show about 40 bar and the pressure should show 30 PSI.
5. Open the red exit valve on the tank.
6. Open the yellow main valve on the tank.
7. Open LN2 container valve on the wall for filling and keep both exit and main valve on the tank open during filling.
8. Put on timer (20-45 min when the pressure is 40-20 bar)
9. Observe tubing for a few minutes after filling started to observe potentially leakage.
10. Once no leaks observed, you can leave the room with both of the doors open, place the chain at the door opening and leave behind your contact info in front of the door.
11. Filling takes about 20 minutes to 1 hour to fill 250 L depending on the pressure and how much liquid nitrogen there is in the container.
12. Make sure to be back before the tank gets overfilled. Overfilling will result in 02 sensor alarm will go off!
13. Once the tank level indicator shows 240/250 L close
    • LN2 container valve on the wall
    • Yellow main valve on the cryo-tank
    • Red exit valve on the cryo-tank
14. Detach the tubing from the tank
15. Lock both doors

Updated by Anna Tran 17.09.19

Edited by PTM 12.09.19

Edited by AT 19.01.23