Liquid Nitrogen Safety Environmental Health and Safety Environmental

Liquid Nitrogen Safety Environmental Health and Safety Environmental Health & Safety

What is Liquid Nitrogen? • Liquefied form of nitrogen (N 2) gas. • When in the gaseous phase, it is a mostly inert gas, that is colorless, odorless, and tasteless. • In the liquid phase, it’s very cold (BP=195. 8°C), which makes it ideal to transport cold materials. – This however, can cause severe frostbite Environmental Health & Safety

Why Take Precautions? • The gas isn’t technically toxic, but it can easily start to replace oxygen in the air so your body can’t breathe in enough oxygen. This can cause affixation very quickly. • Oxygen becomes a liquid at a higher temperature than nitrogen, so liquid oxygen can become encased in liquid nitrogen. These oxygen enriched environments can cause materials to burn rapidly. Environmental Health & Safety

Why Continued • It’s very cold! – Since it’s so cold, any exposure to your skin cause severe frostbite. – It will be very painful. Environmental Health & Safety

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. Environmental Health & Safety

Don’t Forget To • Always follow general lab safety procedures. – (especially the do not drink the chemicals one). • Take your time and be careful! Environmental Health & Safety

Lab Safety Don’ts • Don’t completely seal off the container. – At room temperature, nitrogen is going to create a gas. – This requires exhaust, or the container could potentially explode. Environmental Health & Safety

More Lab Safety Don’ts • 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. Environmental Health & Safety

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. Environmental Health & Safety

Container’s -Dewar • Non pressurized container. • Typical capacity is a liter. • Product may be removed to smaller containers by pouring, but larger sizes require a transfer tube. • A loose fitting dust cap over the outlet prevents moisture from plugging the vent, allowing gas to escape. Environmental Health & Safety

Container’s – Cryogenic Liquid • Insulated, vacuum jacketed pressure vessels. • Operate up to 350 psi and have capacities between 80 -450 L. • Product may be withdrawn as a gas by passing through an internal vaporizer. – Or as a liquid under its own vapor pressure. • Come equipped with safety relief valves and rupture discs. – This protects from pressure build up. Environmental Health & Safety

Container’s – Cryogenic Storage • Typically includes a tank, a vaporizer, and a pressure control manifold. • May be spherical or cylindrical in shape. • Sizes range from 500420, 000 gallons • Powder and vacuum insulated. Environmental Health & Safety

Transfer Lines • Transfer lines are used to remove liquid from Dewar or cryogenic liquid storage containers. • Cryogenic lines are always connected to the cylinder’s liquid withdrawal valve. Environmental Health & Safety

Transfer Lines – Part II • A typical Dewar transfer line is connected to a bayonet. – This provides a means to remove product by pressure build up. • Use only transfer lines designed for cryogenic equipment. *Bayonet for vacuum transfer line Environmental Health & Safety

Transport • Find a cart – Don’t try to carry or roll the container. • Keep upright • Don’t try to pull the container, always push. • Avoid mechanical or thermal shock. – Sudden environmental change could potentially change the pressure. Environmental Health & Safety

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 a diagram of a liquid nitrogen storage tank. Environmental Health & Safety

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. Environmental Health & Safety

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 been emptied. Environmental Health & Safety

Storage Part I • Keep in a well ventilated room – The room shouldn’t be a confined area to help exhaust any nitrogen gas off-gassing from the container. – A non ventilated room could very quickly become oxygen deficient. – It is also recommended that the building that the nitrogen is stored in has an exhaust ventilation system to outside the building. All lab buildings have this system. • Do not leave Dewar containers uncovered, but make sure to have an exhaust system – If the container is completely covered, the pressure could increase to dangerous levels, so exhaust is required. If left completely uncovered, the liquid nitrogen will evaporate much faster. Environmental Health & Safety

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. Environmental Health & Safety

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 a well ventilated area, or outside and acquire a respirator. – Reentry may only occur by trained personnel with air supplying respirators. • If an emergency happens, contact 911 then your lab coordinator and EHS ((740 -593 -1666). – Also, contact your lab coordinator if anything seems out of the ordinary. • If there is a fire call 911. – This is due to the possible asphyxiation hazard. Environmental Health & Safety

Other Resources • http: //www. airproducts. com/responsibility/ehs /productsafetyinformation/safet ygrams. htm • http: //engineering. dartmouth. edu/microengin eering/ln 2. html • http: //www. physics. unc. edu/about/safety/cont ent/N 2 operation. SW_2. pdf Environmental Health & Safety