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October 1, 2019

Storing Liquid Nitrogen in Laboratories: Which Safety Precautions and Sensors Will Protect Your Employees?

Storing Liquid Nitrogen in Laboratories: Which Safety Precautions and Sensors Will Protect Your Employees?

Liquid nitrogen is frequently used in scientific research, chemistry classes, and even culinary arts nowadays. The substance is safe when properly stored, and as long as everyone follows safety protocols while handling the liquid nitrogen. As part of an environmental health and safety review (EHS review), learn safety considerations regarding storing liquid nitrogen in the lab setting.

 

EHS Review: Understand Liquid Nitrogen Risks

Liquid nitrogen is known for its cryogenic properties. It can freeze things incredibly quickly. This property also applies to people, so staff must take safety precautions when handling liquid nitrogen. Even seconds of exposure can damage skin and eye tissue, and may cause frostbite. 

 

Staff should never transport liquid nitrogen in open containers. They should never reach directly into vats of the substance. 

 

The main health risk with liquid nitrogen occurs when the liquid vaporizes into gas, which happens if it leaks into the atmosphere. Nitrogen expands in volume when it turns into gas, and depletes oxygen from the air. The gas has no odor or color, so there is no way staff can tell a leak has occurred without an alarm system. If a nitrogen leak occurs, oxygen levels will fall below safe thresholds. This causes severe cognitive and respiratory problems, as well as death by asphyxiation.

 

Liquid nitrogen, like other cryogenic liquids, needs a pressure-relief valve during storage. Without such a valve, internal pressure could cause the storage tank to explode. Liquid nitrogen should be stored in a room that has proper ventilation as a precaution around leaks. If a leak occurs, the ventilation system can help shunt gases outdoors, protecting the health of workers. 

 

How to Protect Your Employees’ Environmental Health and Safety With an Oxygen Monitor 

Facilities must install, calibrate, and maintain oxygen sensors to comply with safety policies regarding the storage of liquid nitrogen in the lab setting. These units act as a secondary precaution against the dangers of a nitrogen leak. An oxygen deficiency monitor or O2 sensor measures the levels of oxygen in the environment at all times. These devices provide labs with a cost-effective and reliable way to make sure there are no leaks in nitrogen storage areas. 

For safety precautions, install one oxygen deficiency monitor anywhere liquid nitrogen is stored, handled, or used. These monitors mount to the wall quickly and provide continuous sampling of oxygen levels. As long as there is no leak, and the room contains enough oxygen, the monitors stay silent. If nitrogen leaked it would cause a decline in oxygen levels, eventually triggering an alarm and flashing light. The oxygen monitor would provide enough time for anyone working in the area to vacate the premises and avoid being harmed or killed. 

 

While there are several styles of O2 sensor on the market, those from PureAire are preferred for their high quality and cost efficiency. PureAire’s O2 sensors feature zirconium, which lasts for 10+ years on average with no maintenance and no calibration. Once the monitor in installed, there’s nothing more that needs to be done. Since PureAire’s oxygen monitors are reliable once installed, and require less maintenance than the competition, they make it easier and cheaper for labs to protect worker safety. Learn more about PureAire’s products by visiting www.pureairemonitoring.com.

 

  • By : PureAire Monitoring Systems – pureairemonitoring.com
October 1, 2019
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September 16, 2019

Liquid Nitrogen vs. Carbon Dioxide Food Freezing

Liquid Nitrogen and Carbon Dioxide can be used interchangeably in many food freezing applications. However, Liquid Nitrogen often offers many advantages over Carbon Dioxide.

  Liquid Nitrogen Carbon Dioxide
Safety and Environmental Considerations LN2 is chemically inert.
An increase in N2 levels of
2% is not dangerous to humans.
LN2 is much easier to exhaust than C02.		 C02 is faintly reactive and toxic.
OSHA’s carbon dioxide exposure limit in the breathing atmosphere is just 0.5 percent.
If incorrectly sized or operated, dry ice snow may collect on the process room floor.
Recommended Safety Equipment Matheson Tri-Gas recommends an oxygen deficiency monitoring system installed in the processing room for both Liquid Nitrogen and Carbon Dioxide freezing equipment. Matheson Tri-Gas recommends an oxygen deficiency monitoring system installed in the processing room for both Liquid Nitrogen and Carbon Dioxide freezing equipment.
Food Quality Rapid freezing locks in moisture and preserves texture. Slower freezing can negatively affect food quality.
Investment Cost Lower freezing temperatures mean quicker freezing so equipment needed to produce same amount of product is smaller. Smaller size equipment means lower cost. Higher freezing temperatures mean the equipment has to be proportionally larger to achieve the same throughput.
Operating Cost LN2 has about an 18% higher refrigeration value (see chart on back) when compared to C02*. Therefore, on a pound per pound basis, the freezing process would use about 18% less LN2 than C02. Even if LN2 is more expensive than CO2, the price per pound of frozen product can be less using LN2 since the freezing process would use less cryogen.
Maintenance Cost Simple equipment with low maintenance requirements. Complicated equipment requires more maintenance.
Production Rate Lower operating temperatures and shorter dwell time result in almost twice the throughput in the same footprint. For example, a 20 foot LN2 tunnel can deliver the same output as a 30 foot CO2 tunnel Higher operating temperatures and longer dwell time require 50% larger freezer to produce the same amount of product.
Operational Flexibility Smaller freezing equipment leaves more room for expansion.
Simple to operate and user-friendly.
Precise sizing not as critical, can operate efficiently outside of the original design parameters.		 Larger freezing equipment takes up more plant space.
Less user-friendly, requires more vigilant operator.
Freezer must be sized precisely for a specific product and throughput.

*The actual value depends on the pressure of the gas, the type of freezer, the freezer’s operating temperature, and other factors.

 

September 16, 2019
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CryoWest News
August 14, 2019

An Introduction to Cryogenic Hardening

Cryogenic hardening is a process that uses cryogenic temperatures – temperatures below −150 °C (−238 °F ) to strengthen and enhance the grain structure of a metal. Cryogenic treatment of certain metals is known to provide three beneficial effects:

  1. Greater durability: Cryogenic treatment helps to promote the transformation of retained austenite present in heat treated steels into harder martensite steel. This results in fewer imperfections and weaknesses in the steel’s grains structure. 
  2. Improved wear resistance: Cryogenic hardening increases the precipitation of eta-carbides. These are fine carbides that act as binders to support the martensite matrix, helping to resist wear and corrosion resistance. 
  3. Stress relief: All metals have residual stress that is created when it solidifies from its liquid phase into a solid phase. These stresses can result in weak areas that are prone to failure. Cryogenic treatment can reduce these weaknesses by creating a more uniform grain structure. 
 

Process

The process of cryogenically treating a metal part involves very slowly cooling the metal using a gaseous liquid nitrogen. The slow cooling process from ambient to cryogenic temperatures is important in avoiding thermal stress.  

 

The metal part is then held at a temperature of around −190 °C (−310 °F) for 20 to 24 hours before heat tempering takes the temperature up to around +149 °C (+300° F). This heat tempering stage is critical in reducing any brittleness that may be caused due to the formation of martensite during the cryogenic treatment process.

 

Cryogenic treatment changes the entire structure of a metal, not just surface. So the benefits are not lost as a result of further processing, such as grinding.  

 

Because this process works to treat austenitic steel that is retained in a component, it is not effective in treating ferritic and austenitic steels. It is, however, very effective in enhancing heat-treated martensitic steels, such as high carbon and high chromium steels, as well as tool steels.

 

Besides steel, cryogenic hardening is also used to treat cast iron, copper alloys, aluminum, and magnesium. The process can improve the wear life of these types of metal parts by factors of two to six. 

 

Cryogenic treatments were first commercialized in the mid-to-late 1960s. 

 

Applications

Applications for cryogenically treated metal parts include, but are not limited to, following industries: 

 
  • Aerospace and defense (e.g. weapons platforms and guidance systems)
  • Automotive (e.g. brake rotors, transmissions, and clutches)
  • Cutting tools (e.g. knives and drill bits)
  • Musical instruments (e.g. brass instruments, piano wires, and cables)
  • Medical (e.g. surgical tools and scalpels)
  • Sports (e.g. firearms, fishing equipment, and bicycle parts)

 

Source: https://www.thebalance.com/cryogenic-hardening-2340006

August 14, 2019
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freezing bodies
August 14, 2019

What Does Cryopreservation Do To Human Bodies?

Cryonics is one extreme of cryopreservation where the whole body is frozen in the hope that one day it will be possible to revive it.

 

On a smaller scale in day-to-day medicine, freezing is an extremely useful technique for storing living cells, such as blood cells, bone marrow, sperm and embryos, at ultra-low temperatures.

But scientists agree that preserving and reawakening the complete human body is a remote possibility which would take massive breakthroughs in technology.

 

How unlikely?

Prof John Armitage, director of tissue banking at the University of Bristol, believes you can never say never in science but there was little chance of it happening based on current knowledge.

He said taking tissues from healthy people to be stored for future use was one thing but taking a diseased body, freezing it safely – including the complex structure of the brain – and reactivating it was a far, far more difficult task.

“What are the chances there wouldn’t be some damage?” Prof Armitage says.

“We are not even at the stage of cryopreserving organs yet, so doing it with a whole body would be a huge challenge.”

Organs themselves are very complicated, containing different types of cells, blood vessels and an inter-cellular structure – which would all need to be preserved.

Barry Fuller, professor in surgical science and low temperature medicine at University College London, said the first step was to demonstrate that human organs could be cryopreserved for transplantation.

But at the moment the equipment to make that happen is not available, he said.

“This is why we have to say that at the moment we have no objective evidence that a whole human body can survive cryopreservation with cells which will function after rearming,” he said.

 

What happens to the body?

After death, patients have to be acted on quickly.

In the UK, a group of volunteers trained in cryonics takes care of the body, starts the process of freezing and arranges for it to be shipped to the country where it is to be stored.

At this stage, dry ice is used to keep the body at a low temperature.

 

Bodies are cryogenically preserved in liquid nitrogen at extremely low temperatures

 

 

 

 

 

 

 

 

 

 

 

Once at the storage facility, patients are infused with cryoprotectants (like antifreeze) to prevent ice crystal formation – which would kill cells – before the temperature is slowly lowered and they are preserved in liquid nitrogen at extremely low temperatures of below -130C.

The low temperatures are needed to allow the cells to survive dehydration after death – but uncontrolled dehydration and freezing is also lethal to living cells, so it has to be done carefully.

The eventual aim is that one day they will be rewarmed and revived, but there is no evidence or guarantee that they can be.

Several hundred people have already paid to have their bodies cryogenically preserved in three existing facilities in the US and Russia, and there are as many as 1,250 on waiting lists.

Cryonics UK, a non-profit organisation which provides assistance to people in the UK who want their body to be frozen on death, said it has helped 10 people so far.

 

Source: https://www.bbc.com/news/health-38019392

August 14, 2019
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