Liquid Nitrogen Safety

7/30/2019 Liquid Nitrogen Safety

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Environmental Health & Safety

Liquid Nitrogen Safety

Environmental Health and Safety
http://www.ohio.edu/http://www.ohio.edu/


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What is Liquid Nitrogen?

Liquefied form of nitrogen (N2) gas.

When in the gaseous phase, it is a mostlyinert gas, that is colorless, odorless, and

tasteless. In the liquid phase, its very cold (BP=-

195.8C), which makes it ideal to transport

cold materials. This however, can cause severe frostbite


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Why Take Precautions?

The gas isnt technically toxic, but it can easilystart to replace oxygen in the air so your bodycant breathe in enough oxygen. This can cause

affixation very quickly. Oxygen becomes a liquid at a higher

temperature than nitrogen, so liquid oxygen canbecome encased in liquid nitrogen. These

oxygen enriched environments can causematerials to burn rapidly.


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Why Continued

Its very cold!

Since its so cold, any

exposure to your skin

can cause severefrostbite.

It will be very painful.


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Lab Safety Do #1

Wear Safety Gear!

Lab coats can save your body

parts from freezing during an

accidental spill!

Safety goggles are required but

a full face shield is

recommended.

Gloves are also required

preferably cryogenic but leather

will work for smaller scale

applications. Long pants and close toed

shoes are also required.


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Dont Forget To

Always follow general

lab safety procedures.

(especially the do not

drink the chemicalsone).

Take your time and be

careful!


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Lab Safety Donts

Dont completely seal off the container.

At room temperature, nitrogen is going to create

a gas.

This requires exhaust, or the container could

potentially explode.


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More Lab Safety Donts

Funnel the liquid nitrogen

This could potentially cause spills and splashes

that could come into contact with skin.

Dip a hollow tube into the container

Could potentially splatter.


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Nitrogen Containers

Three types of containers

Dewar, Cryogenic Liquid Cylinder, and

Cryogenic Storage Tank

Storage varies from a few liters to thousands.

Vaporization is always continuous.

This is because heat leaks are always present.

Know your specific container and proper

handling procedures.


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Containers Cryogenic Liquid

Insulated, vacuum jacketedpressure vessels.

Operate up to 350 psi and havecapacities between 80-450 L.

Product may be withdrawn as a

gas by passing through aninternal vaporizer.

Or as a liquid under its ownvapor pressure.

Come equipped with safety relief

valves and rupture discs. This protects from pressure

build up.


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Containers Cryogenic Storage

Typically includes atank, a vaporizer, and apressure controlmanifold.

May be spherical orcylindrical in shape.

Sizes range from 500-

420,000 gallons Powder and vacuum

insulated.


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Transfer Lines

Transfer lines are usedto remove liquid fromDewar or cryogenicliquid storagecontainers.

Cryogenic lines arealways connected tothe cylinders liquidwithdrawal valve.


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Transfer Lines Part II

A typical Dewartransfer line isconnected to abayonet. This provides a means

to remove product bypressure build up.

Use only transfer lines

designed for cryogenicequipment. *Bayonet for vacuum transfer line


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Transport

Find a cart

Dont try to carry or roll

the container.

Keep upright Dont try to pull the

container, always push.

Avoid mechanical or

thermal shock. Sudden environmental

change could potentially

change the pressure.


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Handling

Use cryogenic gloves when

operating any valve or any place

of a possible air leak.

Leather gloves can also be

used, but for larger scale

operations use cryogenic.

Be aware of the weight and

design of your specific container.

This can help prevent laboratory

accidents.

The figure on the right is adiagram of a liquid nitrogen

storage tank.


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Gas Withdrawal

1. Connect a control regulator to the gas

withdrawal valve and the outlet of the valve

to the system receiving gas.

2. Open withdrawal and pressure building

valves until the container reaches desire

pressure.

3. You may begin withdrawing gas.


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Liquid Withdrawal

1. Always wear a face mask for liquid withdrawal.

2. Connect a transfer line from the liquid valve to

the system being filled.

3. Open valve to desired rate of flow, close when

finished.

4. To prevent back contamination, all valves

should be closed when the container has beenemptied.


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Storage Part I

Keep in a well ventilated room The room shouldnt be a confined area to help

exhaust any nitrogen gas off-gassing from thecontainer.

A non ventilated room could very quickly becomeoxygen deficient.

It is also recommended that the building that thenitrogen is stored in has an exhaust ventilationsystem to outside the building. All lab buildingshave this system.

Do not leave Dewar containers uncovered,but make sure to have an exhaust system

If the container is completely covered, thepressure could increase to dangerous levels, soexhaust is required. If left completely uncovered,the liquid nitrogen will evaporate much faster.


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Storage Part II

Store in a controlled environment

Away from weather change. This will help the

nitrogen from undergoing drastic changes in

temperature or pressure.


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In Case of Emergency

If your skin comes into contact with liquid nitrogen Thaw slowly with warm water

Always seek medical attention though 911

In case of a lack of oxygen, move immediately to awell ventilated area, or outside and acquire arespirator. Reentry may only occur by trained personnel with air

supplying respirators.

If an emergency happens, contact 911 then your labcoordinator and EHS ((740-593-1666).

Also, contact your lab coordinator if anything seems out ofthe ordinary.

If there is a fire call 911. This is due to the possible asphyxiation hazard.


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Other Resources

http://www.airproducts.com/responsibility/ehs

/productsafety/productsafetyinformation/safet

ygrams.htm

http://engineering.dartmouth.edu/microengin

eering/ln2.html

http://www.physics.unc.edu/about/safety/cont

ent/N2operationSW_2.pdf
http://www.airproducts.com/responsibility/ehs/productsafety/productsafetyinformation/safetygrams.htmhttp://www.airproducts.com/responsibility/ehs/productsafety/productsafetyinformation/safetygrams.htmhttp://www.airproducts.com/responsibility/ehs/productsafety/productsafetyinformation/safetygrams.htmhttp://engineering.dartmouth.edu/microengineering/ln2.htmlhttp://engineering.dartmouth.edu/microengineering/ln2.htmlhttp://www.physics.unc.edu/about/safety/content/N2operationSW_2.pdfhttp://www.physics.unc.edu/about/safety/content/N2operationSW_2.pdfhttp://www.physics.unc.edu/about/safety/content/N2operationSW_2.pdfhttp://www.physics.unc.edu/about/safety/content/N2operationSW_2.pdfhttp://engineering.dartmouth.edu/microengineering/ln2.htmlhttp://engineering.dartmouth.edu/microengineering/ln2.htmlhttp://www.airproducts.com/responsibility/ehs/productsafety/productsafetyinformation/safetygrams.htmhttp://www.airproducts.com/responsibility/ehs/productsafety/productsafetyinformation/safetygrams.htmhttp://www.airproducts.com/responsibility/ehs/productsafety/productsafetyinformation/safetygrams.htmhttp://www.ohio.edu/http://www.ohio.edu/

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Liquid Nitrogen Safety