Even though the hydrogen fueling process is much like fueling a gasoline-powered vehicle, it still will challenge the safety professional to work outside of a controlled workplace setting. (Airgas photo)

Hydrogen Fueling Safety

Hydrogen safety utilizes the same safety concepts as other flammables and cryogenics. Though it’s been around forever, we have only begun to understand its potential.

Energy derived from oil is not sustainable; it contributes to global warming and in some instances, global conflict. In the United States, consumers are primed and ready for the next technological advancement that will provide an energy solution that is renewable, sustainable, and will possibly lead our country to global energy independence. Hydrogen fuel is the promising product.

Even with a potential solution identified, it cannot happen overnight because we need to build our infrastructure of hydrogen production, transportation, and storage facilities to meet the increasing demand. The Hydrogen Council, a group of 18 industry leaders whose focus is to advance the development of a hydrogen economy, outlined a plan to meet these demands in its report "Hydrogen, Scaling Up."1

Various regulatory entities have also done much to ensure the safe handling of hydrogen, but much more will be needed as we develop a variety of uses for hydrogen energy. Like most flammable gases, there are safety concerns to address when managing hydrogen fuel. First, it is important to understand the properties of hydrogen in order to recognize the hazards.

What is Hydrogen?
Hydrogen is the first element in the periodic table. It is the smallest, lightest, most abundant element in the universe. With the symbol H, molecular formula of H2, it exists in molecular forms such as water and organic compounds and requires physical separation from the compound to produce hydrogen gas.

Hydrogen gas is 14 times lighter than air and rises at a rate of about 20 m/s. It is a category 1 flammable gas and has a flammable range of 4% to 75% by volume in air. "If used outside or with good ventilation it will rise at a rate that is 6 times faster than natural gas making it safer to use than most other flammables."2 Hydrogen is odorless, colorless, and tasteless, so it is undetectable when present. It burns with an invisible flame and is extremely dangerous to work around without the aid of hydrogen gas detectors, heat sensors, and other means of identifying leaks and fire.

Hydrogen History
The most recognized use of hydrogen happened in 1961, when President John F. Kennedy launched his support for the space program and the Apollo was built. Since then, NASA has used hydrogen in its space shuttle program with benefits in the use of the fuel as a propellant. Once hydrogen fuel propelled the shuttle into space, the shuttle's fuel cells used hydrogen to produce electricity for the shuttle's energy requirements. The two byproducts from the chemical reaction in the fuel cells are water, which the astronauts drink, and heat, which is used to keep the shuttle environment warm.

On Jan. 28, 2003, President George W. Bush recognized the advancements in hydrogen fuel cell technology and gave his support for it in his State of the Union Address to Congress. He understood its value in reducing our dependence on oil and transitioning to a cleaner, more secure hydrogen energy future. This has since yielded a variety of advancements in hydrogen use.

Modern Hydrogen Applications
Today, motors powered by hydrogen fuel cells are twice as efficient as combustion engines. Bob Oesterreich, U.S. Hydrogen Energy Operations Manager at Air Liquide, provides hydrogen-fueled forklifts for Walmart and other large industries. The benefits of hydrogen forklifts are that they do not require battery recharging, thereby saving the company time and keeping the forklift in operation continuously.

The refueling process for hydrogen powered forklifts takes only 2 minutes, compared to a 15-minute battery charge, and the hydrogen forklift will operate at peak speeds as long as there is fuel, where a battery-operated forklift will wind down as it depletes its charge. Hydrogen forklifts also can operate in freezing temperatures without the worry of battery degradation.

In the last few years, nine automobile companies have begun to build and sell hydrogen-fueled cars. Consumers now have the responsibility of handling hydrogen when fueling their vehicles. Even though the hydrogen fueling process is much like fueling a gasoline-powered vehicle, it still will challenge the safety professional to work outside of a controlled workplace setting. Lastly, with an estimated 9 million metric tons of hydrogen produced and used in the United States today, we can expect that number to rise as the demand for this clean fuel increases.

One of the best resources for identifying the appropriate regulations is the Department of Energy's (DOE) Hydrogen Tools,4 which provides an in depth look at all applicable regulations. The Hydrogen Technologies Safety Guide3,5 also specifically addresses safety regulations in a condensed and simplified manner.

Thermal Hazards and PPE
In this section, we will focus on liquid hydrogen and its six main hazards: thermal, material compatibility, pressure, ice buildup, liquid air hazards, and asphyxiation. Formal training programs are available from the Hydrogen Tools website.4

Hydrogen is a cryogenic that poses thermal hazards to people. Contact with a cryogenic material may produce frostbite and cryogenic burns to human tissue. Proper PPE is necessary to protect against thermal hazards.

Pressure and relief valves
A common phrase used in hydrogen operations is "a cryogenic system is a high pressure system waiting to happen."4 Hydrogen stored inside a bulk tank as a cryogenic liquid can heat up past its boiling point, causing the liquid hydrogen to become a gas that can expand to 850 times its normal liquid volume. This increase in pressure, if not vented, could cause the tank to rupture in an explosive manner. Proper installation and maintenance of pressure relief devices is necessary to reduce the potential for pressure buildup and ensure safe operation of hydrogen systems.

Hydrogen embrittlement and material compatibility
Hydrogen is the smallest element in the universe and as a gas, it has the ability to infuse into many metals and cause them to become brittle—a term called hydrogen embrittlement. Metals such as steel are susceptible to hydrogen and become brittle and fracture when exposed. Addressing compatible metals in the design phase and a management of change program are required to ensure only compatible materials are used in processes containing hydrogen.

Ice buildup and removal
"Ice buildup around cryogenic systems happens when water from air condenses and freezes on system components and piping carrying cryogenic liquids."4 This may cause components to fracture and may freeze valves in place so that they cannot be manipulated, or it may cause vents to freeze and fail to perform properly. Procedures to identify when ice buildup is a hazard and how to prevent or remove ice buildup are necessary to ensure safe operation of the hydrogen system.

Liquid air and prevention
Liquid hydrogen is so cold that it can liquefy the air it comes into contact with. When air is in the liquid form, the nitrogen in the air will evaporate out, leaving the liquid air with a higher than normal amount of oxygen. Oxygen-enriched liquid air is a fire and explosive hazard. Prevent cryogenic liquid from spilling onto asphalt or coming into contact with other combustible materials.

Asphyxiation and ventilation
Liquid hydrogen expands with a 1/850 ratio, causing a rapid buildup of hydrogen gas. In enclosed spaces, this can cause an asphyxiation hazard. Good ventilation, natural or intrinsically safe mechanical ventilation, will assist in preventing asphyxiation hazards. If possible, use hydrogen in outdoor settings and always have appropriate gas detection systems in place.

Unexpected Emergencies and Emergency Action Planning
Lastly, facilities and local fire departments should plan for unexpected emergencies including hydrogen fires and large hydrogen releases. Training materials for first responders that cover hydrogen emergencies and include emergencies involving hydrogen fuel celled vehicles can be found at http://www.nfpa.org/training-and-events/by-topic/alternative-fuel-vehicle-safety-training/emergency-response-guides.

Tomorrow's Challenges
Hydrogen has the highest energy content of any fuel in use today, it's easy to produce, and there are unlimited applications. Hydrogen safety utilizes the same safety concepts as other flammables and cryogenics and, though it's been around forever, we have only begun to understand its potential.

References
1. Study Task Force of the Hydrogen Council. (2017, November). Hydrogen Scaling Up. Retrieved January 25, 2018, from www.hydrogencouncil.com. A sustainable pathway for global energy transition.
2. Increase Your H2IQ. (n.d.). Retrieved Jan. 25, 2018, from https://energy.gov/eere/fuelcells/increase-your-h2iq
3. https://www.h2tools.org/bestpractices/communications/placard
Rivkin, C., Burgess, R., & Buttner, W. (2015, January 1). Hydrogen Technologies Safety Guide (United States, National Renewable Energy Laboratory, Office of Efficiency and Renewable Energy). Retrieved Jan. 25, 2018, from http://www.osti.gov/scitech
4. Home | Hydrogen Tools. (n.d.). Retrieved Jan. 25, 2018, from https://www.h2tools.org/
H2 Tools is intended for public use. It was built and is maintained by the Pacific Northwest National Laboratory with funding from the DOE Office of Energy Efficiency and Renewable Energy's Fuel Cell Technologies Office.
5. https://www.hydrogen.energy.gov/newsletter.html
Hydrogen safety newsletters from the DOE.

This article originally appeared in the July 2018 issue of Occupational Health & Safety.

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