Environmental Health & Safety
18 Oct.,2023
ATTENTION: Use of liquid nitrogen requires online training and the
passing of a liquid nitrogen quiz (located on SOLE). Contact 304-293-0952
for more information.
Defining Cryogenic Liquids
Cryogenic liquids
(also known as cryogens) are gases at normal temperatures and pressures.
However, at low temperatures, they are in their liquid state. These liquids are
extremely cold and have boiling points less than -150°C (- 238°F). Even the vapors
and gases released from cryogenic liquids are very cold. They often condense the
moisture in air, creating a highly visible fog. Different cryogens become liquids
under different conditions of temperature and pressure, but all have two properties
in common; extremely cold and small amounts of liquid can expand into very large
volumes of gas. Everyone who works with cryogenic liquids must be aware of their
hazards and know how to work safely with them.
Types of Cryogenic Liquids
Each cryogenic liquid has its own specific properties but most cryogenic liquids
can be placed into one of three groups:
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Inert Gases: Inert gases do not react chemically to any great extent.
They do not burn or support combustion. Examples of this group are nitrogen,
helium, neon, argon and krypton.
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Flammable Gases: Some cryogenic liquids produce a gas that can
burn in air. The most common examples are hydrogen, methane, carbon monoxide,
and liquefied natural gas.
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Oxygen: Many materials considered as non-combustible can burn in
the presence of liquid oxygen. Organic materials can react explosively with liquid
oxygen. The hazards and handling precautions of liquid oxygen must therefore
be considered separately from other cryogenic liquids.
Personal Protective Equipment to be worn
- Be sure to work in a well ventilated area to prevent oxygen deficient atmospheres
under 19.5% oxygen.
- Wear safety shoes when handling containers along with long sleeve shirts and trousers
without cuffs.
- ALWAYS wear a full face shield and splash resistant safety goggles. Contact lenses
should not be worn.
- Wear a lab coat and an apron when dispensing liquid nitrogen.
- Wear insulated or leather gloves when handling liquid nitrogen or large, cold objects.
Handling Cryogenics Liquids
- Never allow any unprotected part of the body to touch noninsulated pipes or vessels
which contain cryogenic fluids. Tissue damage that results is similar to frostbite
or thermal burns.
- The extremely cold metal will cause flesh to stick fast and tear when one attempts
to withdraw from it.
- Use a suitable hand truck for container movement.
- Do not drop, tip, or roll containers on their sides. Do not remove or interchange
connections. If user experiences any difficulty operating container valve or
with container connections discontinue use and contact supplier. Use the proper
connection.
DO NOT USE ADAPTERS.
- Many substances become brittle and may shatter when cold, sending pieces of the
material flying. Avoid common glass and large, solid plastics.
Storing Cryogenic Liquids
- Store and use with adequate ventilation.
- Do not store in a confined space.
- Cryogenic containers are equipped with pressure relief devices to control internal
pressure. Under normal conditions these containers will periodically vent product.
Do not plug, remove, or tamper with pressure relief device for this could cause
an explosion.
- Containers shall be handled and stored in an upright position.
- Small quantities of liquid nitrogen can be stored in Dewar bottles. Dewar bottles
are hollow-walled glass-lined containers which provide excellent insulation.
Hazards of Cryogenic Liquids
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Extreme Cold Hazard: Cryogenic liquids and their associated cold
vapors and gases can produce effects on the skin similar to a thermal burn. Brief
exposures that would not affect skin on the face or hands can damage delicate
tissues such as the eyes. Prolonged exposure of the skin or contact with cold
surfaces can cause frostbite. The skin appears waxy yellow. There is no initial
pain, but there is intense pain when frozen tissue thaws. Unprotected skin can
stick to metal that is cooled by cryogenic liquids. The skin can then tear when
pulled away. Even non-metallic materials are dangerous to touch at low temperatures.
Prolonged breathing of extremely cold air may damage the lungs.
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Asphyxiation Hazard: When cryogenic liquids form a gas, the gas
is very cold and usually heavier than air. This cold, heavy gas does not disperse
very well and can accumulate near the floor. Even if the gas is non-toxic, it
displaces air. When there is not enough air or oxygen, asphyxiation and death
can occur. Oxygen deficiency is a serious hazard in enclosed or confined spaces.
Small amounts of liquid can evaporate into very large volumes of gas.
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Toxic Hazards: Each gas can cause specific health effects. Refer
to the MSDS for information about the toxic hazards of a particular cryogen.
General Hazards of Cryogenic Liquids
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Fire Hazard: Flammable gases such as hydrogen, methane, carbon
monoxide, and liquefied natural gas can burn or explode. Hydrogen is particularly
hazardous. It forms flammable mixtures with air over a wide range of concentration.
It is also very easily ignited.
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Oxygen-Enriched Air: When transferring liquid nitrogen through
uninsulated metal pipes, the air surrounding a cryogen containment system can
condense. Nitrogen, which has a lower boiling point than oxygen, will evaporate
first. This evaporation can leave an oxygen-enriched condensate on the surface
that can increase the flammability or combustibility of materials near the system,
creating potentially explosive conditions. Equipment containing cryogenic fluids
must be kept clear of combustible materials in order to minimize the fire hazard
potential.
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Liquid Oxygen Hazard: Liquid oxygen contains 4,000 times more oxygen
by volume than normal air. Materials that are usually considered non-combustible
(carbon and stainless steels, cast iron, aluminum, zinc, Teflon (PTFE), etc.) may
burn in the presence of liquid oxygen. Many organic materials can react explosively,
especially if a flammable mixture is produced. Clothing splashed or soaked with
liquid oxygen can remain highly flammable for hours.
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Embrittlement: Rubber, plastic, and carbon steel are some examples
of materials that can be can become brittle and break with very little stress
applied to them. Try to avoid using these materials when working with cryogenic.
If these materials are used, perform an inspection before use.
If you have any questions on cryogenic storage tanks. We will give the professional answers to your questions.