Insurers and Risk Managers

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Forum

Apr 24 2015 - 9:04am
nick

Lessons Learned

Sulfur Deprivation Test - Vessel Failure

A sulfur deprivation test was conducted in a sealed 250 ml vessel. More hydrogen was generated in this process than was anticipated, and the vessel cracked.

Severity: 
Leak: 
Ignition: 

A sulfur deprivation test was conducted in a sealed 250 ml vessel. More hydrogen was generated in this process than was anticipated, and the vessel cracked.

Setting: 
Equipment: 
  • Laboratory Equipment
  • Glassware
Damage and Injuries: 
Probable Cause: 
Characteristics: 
When Incident Discovered: 
Lessons Learned: 

Now, when conducting a sulfur deprivation test, vessels are ventilated to prevent over pressurization and safely facilitate the release of excess hydrogen.

Incorrect Hydrogen Gas Bottle Connected to Glove Box

An individual inadvertently connected a pure hydrogen gas bottle to a chamber/glove box as opposed to a 10% hydrogen (in nitrogen) bottle that should have been used. [The wrong bottle had mistakenly been delivered, and the inexperienced...

Severity: 
Leak: 
Ignition: 

An individual inadvertently connected a pure hydrogen gas bottle to a chamber/glove box as opposed to a 10% hydrogen (in nitrogen) bottle that should have been used. [The wrong bottle had mistakenly been delivered, and the inexperienced individual did not know the difference.] The hydrogen concentration increased within the chamber to about 9%. Since there was insufficient oxygen in the chamber to support combustion, the hydrogen did not burn, and was quickly diluted with nitrogen.

Setting: 
Equipment: 
  • Ventilation System
  • Glove Box/Fume Hood
Damage and Injuries: 
Probable Cause: 
Characteristics: 
When Incident Discovered: 
Lessons Learned: 

This incident led to several changes in procedure:

  • The purity of any gas bottle connected is double-checked. The practice outlined in the SOP requires confirming the content of the cylinder via the cylinder label prior to connection to the glove box. Increased attention is now paid during training of new staff members to ensure that this procedure is well understood.
  • The vacuum pump is kept off so that the dilute gas will mix with the hydrogen
  • Alarms are set at 10% hydrogen and at 300 ppm oxygen.
  • A new SOP has been written.
Ti-doped Sodium Alanate Incident

An incident occurred when Ti-doped sodium alanate was exposed to air, apparently resulting in an unstable compound that experienced a rapid exothermic reaction.

The sample consisted of mechanically milled NaAlH4 with 4% TiCl3 dopant which...

Severity: 
Leak: 
Ignition: 

An incident occurred when Ti-doped sodium alanate was exposed to air, apparently resulting in an unstable compound that experienced a rapid exothermic reaction.

The sample consisted of mechanically milled NaAlH4 with 4% TiCl3 dopant which was prepared in an argon atmosphere. The sample was sealed and placed in the probe head of an NMR magic angle-spinning (MAS) rotor and spun at approximately 9,000-13,000 rpm. During the process, the sealing cap dislodged and exposed the sample to ambient air for a little less than 24 hours. When discovered, the sample was visually inspected and showed no evidence of oxidation. The sample was re-capped and returned to an argon environment for removal. Most of the sample material was removed using a small stainless steel needle, but a residual amount, roughly 25 mg sodium alanate, proceeded to undergo a rapid exothermic reaction. No damage resulted to the tube, the glove box or the scientist.

The lab does not know the composition of the material after exposure to the ambient air nor the ignition energy needed to initiate the reaction. However, it appeared that this material underwent a rapid exothermic reaction requiring very little ignition energy.

Aside from exposing this safety hazard, and the relatively minor incident, laboratory personnel pointed out the advantage of working with small samples.

The lab is planning to study this phenomenon, including the running of a time-of-flight mass spectrographic study, to determine what occurred. It will be important for the community at large to be aware of any potentially unknown hazards of working with these materials. The lab believes that the slow exposure to room air is the greatest concern. While loose powder samples will quickly react with the air and ignite, this tightly packed powder indicated no signs of reactivity.

Setting: 
Equipment: 
  • Ventilation System
  • Glove Box/Fume Hood
Damage and Injuries: 
Probable Cause: 
Characteristics: 
When Incident Discovered: 
Lessons Learned: 
  • One needs to take extreme care with both new and supposedly spent hydride samples; the spent materials may contain pockets of unoxidized alanates that could react violently when being transferred.
  • Work with small samples so if something does go wrong, the possibility of serious injury is low.
  • The lab believes that the slow exposure to room air is the greatest concern.

Additional discussion about working with reactive metal-hydride materials in the laboratory can be found in the Lessons Learned Corner on this website and in the Hydrogen Safety Best Practices Manual.

Ammonia Tank Leak

A laboratory had an incident with an ammonia tank. When the valve was opened, the packing in the valve apparently "moved," and a faint ammonia smell was noticed. The tank was returned to the supplier.

Severity: 
Leak: 
Ignition: 

A laboratory had an incident with an ammonia tank. When the valve was opened, the packing in the valve apparently "moved," and a faint ammonia smell was noticed. The tank was returned to the supplier.

Setting: 
Equipment: 
  • Piping/Fittings/Valves
  • Valve
Damage and Injuries: 
Probable Cause: 
Contributing Factors: 
Characteristics: 
When Incident Discovered: 
Lessons Learned: 
  • Valve packing on ammonia tanks should be checked on a regular basis.
  • If an ammonia smell becomes noticeable, the tank should be returned to the supplier.
Hydrogen Cylinder Fire in Laboratory

An employee of an incubator company that was working in a university-owned laboratory facility was checking the hydrogen pressure through the main valve on a hydrogen cylinder. The regulator on this cylinder had not been properly closed. Hydrogen...

Severity: 
Leak: 
Ignition: 
2004

An employee of an incubator company that was working in a university-owned laboratory facility was checking the hydrogen pressure through the main valve on a hydrogen cylinder. The regulator on this cylinder had not been properly closed. Hydrogen escaped through the regulator and was ignited. The fire was contained in the laboratory and extinguished by the building's fire sprinkler system before fire crews arrived. There were no injuries, and damage estimates were not available.

Setting: 
Equipment: 
  • Hydrogen Storage Equipment
  • Gas cylinder
Damage and Injuries: 
Probable Cause: 
Characteristics: 
When Incident Discovered: 
Lessons Learned: 

Incident investigation findings for corrective actions were:
1. Install a valve after the regulator as an added precaution.
2. Clean the coupler at the end of the hydrogen delivery tube after each use to ensure that any catalyst residue has been removed.

Hydrogen Tubing Leak

A facility uses small crucibles to heat precious metals within a fume hood, with natural gas as the fuel source for the Bunsen burner. Hydrogen is fed into the crucible at low pressure (<20 psi) to control the atmosphere within the vessel in...

Severity: 
Leak: 
Ignition: 
2005

A facility uses small crucibles to heat precious metals within a fume hood, with natural gas as the fuel source for the Bunsen burner. Hydrogen is fed into the crucible at low pressure (<20 psi) to control the atmosphere within the vessel in order to prevent oxidation. The hydrogen is routed through a manifold with flexible tubing, which is connected to a ceramic tip and fitted into the crucible through a small opening in the crucible's lid. The hydrogen is consumed in the process. The facility believes that the hydrogen tubing developed a leak which eventually ignited. The plastic interior of the fume hood ignited and started to spread. The person working in the area shut off the natural gas and hydrogen (they had valves at the hood) and used a halon extinguisher in the hood.

Setting: 
Equipment: 
  • Piping/Fittings/Valves
  • Flexible Tubing
Damage and Injuries: 
Probable Cause: 
Contributing Factors: 
Characteristics: 
When Incident Discovered: 
Lessons Learned: 
  1. Flexible tubing should be secured so it cannot get dislodged during operations.
  2. Fume hoods where hydrogen is used should not be made of combustible materials. 3. Preventative maintenance should be performed on equipment on a regular basis to ensure that is is in good working condition.
Hole In Ampoule Leads to Explosion

A researcher was working with hydrogen storage materials in a laboratory. Several other researchers were working in adjacent laboratories.

The researcher had prepared a sample of aluminum deuteride, AlD3, by reacting lithium aluminum...

Severity: 
Leak: 
Ignition: 
2005

A researcher was working with hydrogen storage materials in a laboratory. Several other researchers were working in adjacent laboratories.

The researcher had prepared a sample of aluminum deuteride, AlD3, by reacting lithium aluminum deuteride and aluminum chloride in diethyl ether. The actual composition/phase of the material synthesized was unknown, but the researcher had attempted to produce the gamma phase of aluminum deuteride. The synthesis steps used to produce the material were complete and the researcher attempted to seal the material in a glass ampoule for offsite shipment and analysis. The sample size was approximately 1 gram.

The ampoule with the sample had previously been placed under vacuum and had been isolated from the atmosphere. The process for sealing the ampoule was to first place the sample-containing ampoule in a liquid nitrogen bath to cool the sample down to near 77K. The ampoule was then removed from the liquid nitrogen and a torch was used to melt the neck of the ampoule to seal it. The ampoule was slowly rotated while heat was applied to the neck of the ampoule. Typically, this results in collapse of the ampoule, sealing the sample. However, in this instance, a bubble formed where the heat was applied and a hole formed in the ampoule. This allowed air to enter the previously evacuated container.

After about 30 seconds the ampoule “exploded” and glass from the container was sprayed outward. Some of the shards embedded into the researcher’s arms, face and torso (the researcher was wearing safety glasses, but no other safety equipment). Other researchers working in an adjacent laboratory heard the noise and came to see what had happened. The researcher was taken to the hospital and treated. Larger shards of glass were removed and the injured area was cleaned in an effort to remove the smaller pieces of glass. The researcher stayed home the next day, but returned the second day after the incident. There appears to be no permanent damage to the researcher and he/she is continuing work in the laboratory.

Setting: 
Equipment: 
  • Laboratory Equipment
  • Glassware
Probable Cause: 
Characteristics: 
When Incident Discovered: 
Lessons Learned: 
  • Metal hydride materials of a composition which is not well characterized should be handled with procedures that assume a "worst case" for that class of materials, intermediates or precursors.
  • Laboratory procedures should be in written form and should be adopted only after performing a safety vulnerability analysis and adopting appropriate risk mitigation steps.
  • Working with small amounts of material does not provide assurance of safety.
  • The method described to seal samples that are highly reactive upon exposure to air is not recommended. An alternative method, that is now being used for packaging aluminum hydride samples for offsite shipment is as follows: Aluminum hydride powders (0.5 g - 1.0 g) are sealed in glass bottles with a cap. The bottles are sealed in a thick plastic bag under Ar using a plastic bag sealer in the glove box. The sample bags are then removed from the glove box and sealed under vacuum in a much larger plastic bag using a vacuum sealer. The purpose of the large evacuated bag is to contain any evolved hydrogen gas if the material begins to decompose and the internal bottle & bag rupture. It is a good idea to calculate the maximum volume of H2 (at 1-atm) that could be released by the sample to determine if the outer bag is sufficiently large to contain the evolved gas. The package is then inserted into a cardboard box of sufficient volume (about 1-liter) to accommodate the expanded outer bag.

Additional discussion about working with reactive metal-hydride materials in the laboratory can be found in the Lessons Learned Corner on this website and in the Hydrogen Safety Best Practices Manual.

Liquid Hydrogen Storage Tank Failure

A liquid hydrogen tank’s rupture disc failed prematurely, which caused the tank to vent its entire gas contents through the tank’s vent stack. Venting was very loud and formed a condensed moisture cloud visible from the top of the stack. Liquid...

Severity: 
Leak: 
Ignition: 
2005

A liquid hydrogen tank’s rupture disc failed prematurely, which caused the tank to vent its entire gas contents through the tank’s vent stack. Venting was very loud and formed a condensed moisture cloud visible from the top of the stack. Liquid air was also visible coming off the stack. Venting ceased after approximately 5 minutes. On-site staff called the fire department, which arrived promptly and evacuated the area. Normal operations resumed after the Fire Department was able to determine there were no unsafe conditions.

Setting: 
Equipment: 
  • Hydrogen Storage Equipment
  • Vessel
Damage and Injuries: 
Probable Cause: 
Contributing Factors: 
Characteristics: 
When Incident Discovered: 
Lessons Learned: 
  • A redundant safety circuit was put into service and the tank returned to normal operation after the failure. Both rupture discs were replaced and the tank was inspected.
  • Important to note that the safety system functioned as intended. Most prevalent learning is that liquid air will form and fall off the vent stack due to very high flow of very cold gas when the relief systems are flowing at capacity. Liquid air may also splash off flanges or other pieces and will cause a small vapor cloud as it falls from the stack. Falling liquid air was mistaken for liquid hydrogen during the event.
Hydrogen Cylinder Leak

A hydrogen cylinder was initially located in an adjacent laboratory, with tubing going through the wall into the laboratory in use. When the cylinder was moved to the laboratory in use, a required leak check was not performed. Unfortunately, a...

Severity: 
Leak: 
Ignition: 
Ignition Source: 
Spark from pulling computer power plug from outlet

A hydrogen cylinder was initially located in an adjacent laboratory, with tubing going through the wall into the laboratory in use. When the cylinder was moved to the laboratory in use, a required leak check was not performed. Unfortunately, a leak had developed that was sufficient to cause an accumulation of hydrogen to a level above the Lower Flammability Limit. The hydrogen ignited when a computer power plug was pulled from an outlet. The exact configuration of the leak location and the outlet plug is unknown.

Setting: 
Equipment: 
  • Hydrogen Storage Equipment
  • Gas cylinder
Damage and Injuries: 
Probable Cause: 
Characteristics: 
When Incident Discovered: 
Lessons Learned: 

Hazard analysis should consider potential leak locations, potential ignition sources in the vicinity, and the potential for accumulating flammable gases in that area.

Users should leak-check all cylinders upon installation. This event would have been avoided if personnel had followed internal procedures/requirements.

Hydrogen Storage -Ammonia Borane (AB) Loaded onto Mesoporous Carbon

During preparation of a new hydrogen storage material, ammonia borane (AB) loaded onto mesoporous carbon, an unexpected incident was observed. As with all procedures with new materials the work is conducted on a small scale and in a laboratory...

Severity: 
Leak: 
Ignition: 
2005

During preparation of a new hydrogen storage material, ammonia borane (AB) loaded onto mesoporous carbon, an unexpected incident was observed. As with all procedures with new materials the work is conducted on a small scale and in a laboratory fume hood. They followed the procedures that they had used for absorption of ammonia borane onto mesoporous silica without incident.

To absorb the solid AB into a scaffold material they dissolve AB in a dry aprotic polar solvent, THF. The saturated solution of AB in THF is added to the mesoporous carbon material in a round bottom flask, stirred for 10 minutes to saturate the mesoporous scaffold with AB and then the solvent is slowly removed under vacuum. At this point the sample is assumed to be prepared and ready for transfer to a sample vial for storage.

The material (1:1 mesoporous carbon:AB) was exposed to the atmosphere for close to five minutes without incident and the round bottom flask containing the material was cool to the touch as they have always noted for the silica materials. In order to transfer the material from the round bottom flask to the storage vessel a stainless steel spatula was introduced to the round bottom flask. Upon touching the stainless steel spatula against the inside of the flask, the flask became warm to touch and then a small flame was observed to arise from the round bottom flask. The flask was immediately placed under a large glass crystallizing dish to remove oxygen and the flame was extinguished. After the flame was extinguished, the flask was then placed under nitrogen atmosphere.

Dry carbon materials have been reported to develop a static charge under vacuum. It is likely that using the metal spatula provided a grounding source to release the charge. This static charge may have been responsible for the flame and any exothermic reaction. Likely residual THF ignited.

Setting: 
Equipment: 
  • Laboratory Equipment
  • Glassware
Damage and Injuries: 
Characteristics: 
When Incident Discovered: 
Lessons Learned: 

In the future, this mesoporous carbon material and ammonia borane:mesoporous carbon material will be handled under anaerobic conditions (glove box) to prevent further incidents.

Codes & Standards

American Institute of Aeronautics and Astronautics

American Society of Mechanical Engineers

American Society for Testing and Materials International - Committee D03 Gaseous Fuels / D03.14 Hydrogen and Fuel Cells

Basic Hydrogen Properties Chart

Download the information in Excel format: Hydrogen Properties

Properties

Values

Units

Autoignition temperatureThe autoignition temperature depends on hydrogen concentration (minimum at stoichiometric combustion conditions), pressure, and even the surface characteristics of the vessel. See NFPA 2: Hydrogen Technologies Code 2016 Edition Annex D.

500

°C

932

°F

Boiling point (1 atm)NIST Chemistry WebBook

-252.9

°C

-423.2

°F

Density (NTP)NTP (normal temperature and pressure) = 20°C (68°F) and 1 atm. NIST Chemistry WebBook

0.08375

kg/m³

0.005229

lb/ft³

Diffusion coefficient in air (NTP)NTP (normal temperature and pressure) = 20°C (68°F) and 1 atm. National Aeronautical and Space Administration, Safety Standard for Hydrogen and Hydrogen Systems (NSS 1740.16), 1997

0.610

cm²/s

6.57 E-4

ft²/s

Enthalpy (NTP)NTP (normal temperature and pressure) = 20°C (68°F) and 1 atm. NIST Chemistry WebBook

3858.1

kJ/kg

1659.8

Btu/lb

EntropyNTP (normal temperature and pressure) = 20°C (68°F) and 1 atm. NIST Chemistry WebBook

53.14

J/g-K

12.70

Btu/lb-°R

Flame temperature in airNational Aeronautical and Space Administration, Safety Standard for Hydrogen and Hydrogen Systems (NSS 1740.16), 1997

2045

°C

3713

°F

Flammable range in airNTP (normal temperature and pressure) = 20°C (68°F) and 1 atm. National Aeronautical and Space Administration, Safety Standard for Hydrogen and Hydrogen Systems (NSS 1740.16), 1997

4.0 - 75.0

vol%

Ignition energy in airHydrogen Fuel Cell Engines and Related Technologies. Module 1: Hydrogen Properties. U.S. DOE. 2001

2.0 E-5

J

1.9 E-8

Btu

Internal Energy (NTP)NTP (normal temperature and pressure) = 20°C (68°F) and 1 atm. Reference state: Internal Energy U=0 at 273.16 K for saturated liquid; Entropy S=0 at 273.16 K for saturated liquid. NIST Chemistry WebBook

2648.3

kJ/kg

1139.3

Btu/lb

Molecular weightNIST Chemistry WebBook

2.02

Specific gravity (air = 1) (NTP)NTP (normal temperature and pressure) = 20°C (68°F) and 1 atm. Hydrogen Fuel Cell Engines and Related Technologies. Module 1: Hydrogen Properties. U.S. DOE. 2001

0.0696

Specific volume (NTP)NTP (normal temperature and pressure) = 20°C (68°F) and 1 atm. NIST Chemistry WebBook

11.94

m³/kg

191.26

ft³/lb

Specific heat at constant pressure, Cp (NTP)NTP (normal temperature and pressure) = 20°C (68°F) and 1 atm. NIST Chemistry WebBook

14.29

J/g-K

3.415

Btu/lb-°R

Specific heat at constant volume, Cv (NTP)NTP (normal temperature and pressure) = 20°C (68°F) and 1 atm. NIST Chemistry WebBook

10.16

J/g-K

2.428

Btu/lb-°R

Thermal conductivity (NTP)NTP (normal temperature and pressure) = 20°C (68°F) and 1 atm. NIST Chemistry WebBook

0.1825

W/m-K

0.1054

Btu/ft-h-°R

Viscosity (NTP)NTP (normal temperature and pressure) = 20°C (68°F) and 1 atm. NIST Chemistry WebBook

8.813 E-5

g/cm-sec

5.922 E-6

lb/ft-sec

Questions & Answers

Which ASME B31 piping code should be used for repair and alteration of hydrogen piping systems?

The code used for repair and alterations of an existing system depends on the code used for construction as well as on the requirements imposed by the jurisdiction.

Code of Construction

Generally Accepted Code for Repair and Alterations

ASME B31.1

ASME B31.1, Nonmandatory Appendix V – Recommended Practice for Operation, Maintenance, and Modification of Power Piping Systems

ASME B31.3

API 570 – Piping Inspection Code: In-Service Inspection, Rating, Repair and Alteration of Piping Systems

ASME B31.12

ASME B31.12, Chapter GR-5 – Operation and Maintenance

Other Code

Unless otherwise specified, the same as requirements for new construction.

Note that getting a permit from the jurisdiction may be necessary for an extensive alteration.

Which ASME B31 piping code should be used for changing the rating of hydrogen piping systems?

The requirements of the code used for the original construction apply. The piping may meet the requirements of more than one code. In which case, the code used for changing the rating may be different than the original code of construction. In any case, the re-rated system should meet all of the requirements of the selected code. Note that if the original proof test of the system was not high enough meet the requirement for the new service, the piping will have to be tested at the higher pressure.

Which ASME B31 Code should be used for the construction of hydrogen piping systems?

At least three of the ASME B31 piping codes are logical choices:

  • ASME B31.1, Power Piping
  • ASME B31.3, Process Piping
  • ASME B31.12 Hydrogen Piping and Pipelines

Considerations for code selection include:

  • Requirements imposed by the authority having jurisdiction, whether by direct reference or by reference from another applicable code or standard.
  • Code(s) used for other piping systems at the site. The people who have to operate and maintain the piping will be better served with fewer piping codes. The piping codes are complex and have different requirements. The people who have to operate and maintain the piping will likely be more successful if they have to learn requirements from fewer codes.

In the absence of these factors, ASME B31.12 is probably the most logical choice.

All three codes are suitable for liquid and gaseous hydrogen at pressures 15,000 psi (100 MPa) and higher. For pressures higher than 15,000 psi (100 MPa), the designation of high pressure fluid service in accordance with Chapter IX of ASME B31.3 may be a more economical choice and should be considered.

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Best Practices

Best Practices Overview

What is a best practice?

A best practice is a technique or methodology that has reliably led to a desired result. Using best practices is a commitment to utilizing available knowledge and technology to achieve success.

What is H...

What is a best practice?

A best practice is a technique or methodology that has reliably led to a desired result. Using best practices is a commitment to utilizing available knowledge and technology to achieve success.

What is H2Tools.org/BestPractices?

A wealth of knowledge and experience related to safe use and handling of hydrogen exists as a result of an extensive history in a wide variety of industrial and aerospace settings. Hydrogen is gaining increasing attention worldwide as a possible energy storage medium, for later conversion to electricity through fuel cells or for use as a combustion fuel. This focus has introduced many new participants to research, development, demonstration, and deployment of hydrogen technologies (e.g., fuel cell vehicles and stationary fuel cells).

The purpose of the Hydrogen Safety Best Practices online manual is to share the benefits of extensive experience by providing suggestions and recommendations pertaining to the safe handling and use of hydrogen. Best Practices have been compiled from a variety of resources, many of which are in the public domain and can be downloaded directly from the References section. Many others can be obtained via reference links found at various places within the manual.

Best PracticesA technique or methodology that has reliably led to a desired result are organized under a number of hierarchical categories in this online manual, beginning with those displayed down the left-hand column. Because of the interdependence of the topical areas, however, individual pages are often accessible via multiple internal links. A web-based electronic document format lends itself well to this type of overlapping content.

Website features

Please notice the tool tip featurePlease notice the tool tip feature on this website. When a word in the text appears in green underlined font, you can see its definition by clicking or tapping the word. on this website. When a word in the text appears in green fontPlease notice the tool tip feature feature on this website. When a word in the text appears in green underlined font, you can see its definition by clicking or tapping the word., you can see its definition by clicking or tapping the word. All the definitions are compiled into a Glossary that can be accessed from the References section of every page. There is also an Acronyms list and a Bibliography that can be accessed from every page. When you click on the link to the Bibliography, it will take you to the alphabetized list of references for the particular section from which you accessed it. Please contact us if you notice any definitions, acronyms, or references that should be in these lists but aren’t.

A word about safety

Following the best practices contained in this online manual represents a commitment to the safe use and handling of hydrogen, but it should be recognized that no information resource can provide 100% assurance of safety. Personnel with applicable expertise should always be consulted in designing and implementing any system carrying a potential safety risk. Additionally, since following these best practices does not guarantee compliance with local codes, standards, and regulations, users should check with their local Authority Having Jurisdictionan organization, office, or individual responsible for enforcing the requirements of a code or standard, or for approving equipment, materials, an installation, or a procedure. to ensure that those requirements are adequately addressed.

This online manual is linked to a companion website, Hydrogen Lessons Learned (H2LL), to provide unambiguous illustration of the importance of following safe practices and procedures when working with and around hydrogen. Like virtually all energy forms, hydrogen can be used safely when proper procedures and engineering techniques are followed, but its use still involves a degree of risk that must be respected. The importance of avoiding complacency and/or haste in the safe conduct and performance of projects involving hydrogen cannot be overstated.

So You Want to Know Something about Hydrogen

This material is meant to supplement (not replace) the safety policies and practices of the organizations for which you may be working.

This introductory section provides a starting point for those who are not familiar with hydroge...

This material is meant to supplement (not replace) the safety policies and practices of the organizations for which you may be working.

This introductory section provides a starting point for those who are not familiar with hydrogen. Our target audience is students, technicians, and young engineers who are just getting started in a job that entails working with or around hydrogen. This section presents basic information about hydrogen under two subsections --- Hydrogen Basics and Hydrogen Hazards. The Hydrogen Basics section highlights the properties and behavior of gaseous and liquid hydrogen. It also summarizes historical and current applications of hydrogen as well as common hydrogen storage systems and the controls used to safely maintain them. The Hazards subsection contains information about hydrogen leaks, flames, and explosions. This information is not intended to dissuade you from working with hydrogen, but to make you aware that constant vigilance is necessary when working with or around hydrogen. In fact, hydrogen is just as safe as gasoline or any other commonly used fuel, it's just different. If you understand the differences, you will understand how to work safely with hydrogen.

Each subsection presents a brief overview of the subject matter as a series of simple bullets enhanced with photos and graphics. Links are provided to more detailed information in other sections of the website. Relevant references (either actual PDF files or links to materials on the Internet) are provided underneath. An outline of the subject matter covered in this introductory section is provided below, along with a list of some good safety practices for working with hydrogen.

Hydrogen Basics

Hydrogen Hazards

Good Safety Practices for Working with Hydrogen

  • Always wear appropriate personal protective equipment (PPE) for the specific hazards of your job. Typically there are no specific PPE requirements for working with gaseous hydrogen, other than wearing safety glasses or goggles when working with a compressed gas. However, when working with liquid hydrogen, insulated gloves and protective shoes should be worn in addition to eye protection.
  • Anyone working with hydrogen should have been provided with some basic hydrogen safety training (see Safety Culture) and should be familiar with the basic properties of hydrogen (see Facility Design).
  • New hydrogen users should have clear guidance and instructions from their supervisor or mentor on the required training and approvals necessary before working with hydrogen. Ask for clarification of any unclear guidance, instructions, or responsibilities.
  • Regardless of what kind of project you are working on, you should use a graded approach to safety planning and risk assessment based on the quantities of hydrogen involved (see Safety Planning).
  • The first time you work with hydrogen, you should ask someone with hydrogen experience to assist you. You should never take chances or shortcuts.
  • Always plan for the worst-case scenario, but give some thought to the most probable scenario and be ready for that as well.
Hydrogen Basics

This subsection highlights the properties and behavior of gaseous and liquid hydrogen. It also summarizes historical and current applications of hydrogen as well as common hydrogen storage systems and the controls used to safely maintain them.

...

This subsection highlights the properties and behavior of gaseous and liquid hydrogen. It also summarizes historical and current applications of hydrogen as well as common hydrogen storage systems and the controls used to safely maintain them.

Gaseous Hydrogen Properties and Behaviors

Some basic properties and behaviors of gaseous hydrogen are highlighted on this page. For more information on hydrogen properties, see Hydrogen Compared with Ot...

Some basic properties and behaviors of gaseous hydrogen are highlighted on this page. For more information on hydrogen properties, see Hydrogen Compared with Other Fuels.

  • Hydrogen is a gas at ambient conditions.
  • It is the lightest molecule in the universe.
  • It is 14 times lighter than air, so it rises at almost 20 meters per second (44 miles per hour) and disperses rapidly. This buoyancy is a built-in safety advantage in an outside environment.
  • It is colorless, odorless, tasteless, and undetectable by human senses.
  • It is non-toxic and non-poisonous; however, it can be an asphyxiant.
  • It is flammable and explosive over a wide range of concentrations, so it should be safely stored and used in an area that is free of heat, flames, and sparks.
  • It is non-corrosive, but it can embrittle some metals (i.e., cause significant deterioration of the metal's mechanical properties).

Photo: Figure 1 - Relative Vapor Density
Figure 1. Relative Vapor Density

Glossary
  • Active Ventilation - intentional movement of air using fans, blowers or other mechanical devices. Also called mechanical or forced ventilation.
  • Administrative Controls - procedures or rules that are...
  • Active Ventilation - intentional movement of air using fans, blowers or other mechanical devices. Also called mechanical or forced ventilation.
  • Administrative Controls - procedures or rules that are to be followed to reduce the risks associated with a hazard for which engineering controls are not practical or possible. Although administrative controls can (and should) always be used to control employee exposure, they are prone to human error and cannot be relied upon to reduce exposure all the time. Examples of administrative controls include policies restricting access and signage.
  • Authority Having Jurisdiction - an organization, office, or individual responsible for enforcing the requirements of a code or standard, or for approving equipment, materials, an installation, or a procedure.
  • Bayonet Joint - a high-performance joint, called the bayonet joint, originally developed by Dr. Herrick L. Johnston (J.C. Daunt and H.L.Johnston (1949). Rev. Sci. Instr., v.20, pg.122), is used for lines that must be dismantled frequently or for applications in which a low heat inleak at the joint is required. The bayonet joint consists of a male portion that telescopes within the female portion. The clearance between the male and female portions is made such that no liquid can flow into the space, and gaseous convection is suppressed.
  • Bellow - the flexible element of an expansion joint consisting of one or more convolutions and the end tangents, if any.
  • Best Practice - a technique or methodology that has reliably led to a desired result
  • Blast Wave - a shock wave in air, caused by the detonation of explosive material
  • Buddy System - A system of organizing employees into work groups in such a manner that each employee of the work group is designated to be observed by at least one other employee in the work group. The purpose of the buddy system is to provide rapid assistance to employees in the event of an emergency. It is important that the employee designated as observer not be subject to hazards in the work area.
  • Buoyancy - the tendency of a gas to rise in air
  • Change Control - process or procedure to manage changes being made, including the submission, analysis, decision-making, approval, and implementation of the change. Uncontrolled changes are one of the most common causes of project failure.
  • Charpy Impact Test - a destructive test of impact resistance, consisting of placing the specimen in a horizontal position between two supports, then applying blows of known and increasing magnitude until the specimen breaks
  • Chronic Maintenance - the need for frequent, repeated maintenance on a piece of equipment
  • Compressed Hydrogen Gas - hydrogen compressed to a high pressure and stored at ambient temperature
  • Consequence - the extent to which an event causes injury or damage.
  • Cryogenic Liquid - a liquid with a boiling point below -150° C (-238° F). Note that liquid hydrogen is at -423° F
  • Deflagration - a flame moving through a flammable mixture
  • Detonation - an exothermic chemical reaction coupled to a shock wave that propagates through a mixture of fuel and oxidizer
  • Dewar - a non-pressurized vacuum-jacketed container used to hold cryogenic liquids
  • Diffusion in Air - gradual mixing of gas molecules in air due to random thermal motion
  • Energy Isolating Device - a mechanical device that physically prevents transmission or release of energy (e.g., a control valve)
  • Engineering Controls - controls designed to eliminate or reduce exposure to a hazard through the use or substitution of engineered machinery or equipment. Examples of engineering controls include ventilation systems (fume hoods), sound-dampening materials to reduce noise levels, and safety interlocks.
  • Expansion Joint - any device containing one or more bellows used to absorb dimensional changes, such as those caused by thermal expansion or contraction of a pipeline, duct, or vessel
  • Fail Safe Designs - any failures will leave a system in a condition that will be safest for personnel and will cause the least amount of property damage.
  • Fit for Maintenance - Piping and equipment in hydrogen service should be purged with an inert gas prior to being taken offline for maintenance. Cryogenic vessels should be drained and warmed to ambient temperature.
  • Flameout - accidental extinguishment of a pilot flame on a flare system
  • Formalized Hydrogen Training Plan - a formalized hydrogen training plan may include: 1) pressure safety, 2) cryogenic system safety, and 3) electrical worker training. The formalized training plan should require that classes are updated and personnel are re-certified periodically.
  • Hazard - an object or situation that is potentially dangerous (i.e., an unsecured electrical cord might be a tripping hazard, or a finger-tight connection that is not in a properly vented area might start to leak into an enclosed space, leading to a flammable accumulation of hydrogen)
  • Hot Work - work involving electric or gas welding, cutting, brazing, or similar flame- or spark-producing operations
  • Hydrogen Embrittlement - the ability of hydrogen to cause significant deterioration in the mechanical properties of metal
  • Incident - an event that results in:
    • a lost-time accident and/or injury to personnel
    • damage to project equipment, facilities or property
    • impact to the public or environment
    • an emergency response or should have resulted in an emergency response
  • Inherent Safety Features - system design such that in both normal and emergency situations at least two failures must occur before injury, loss of life, or major equipment damage would result from the use of hazardous materials
  • Likelihood - the chance that an event might happen
  • Lockout - placement of a lock on an energy isolating device
  • Management of Change (MOC) - a formal process for systematically managing variances and changes to materials, technology, equipment, procedures, personnel and facility operation for their effect on safety vulnerabilities
  • Maximum Allowable Working Pressure (MAWP) - the maximum gauge pressure permissable in a pressure vessel
  • Mean Time Between Failures (MTBF) - average calendar time from the onset of one failure to the onset of the next, including time to repair
  • Near-Miss - an event that, under slightly different circumstances, could have become an incident. Examples include:
    • any unintentional hydrogen release that ignites, or is sufficient to sustain a flame if ignited, and does not fit the definition for an incident
    • any hydrogen release which accumulates above 25% of the lower flammability limits within an enclosed space and does not fit the definition of an incident
  • Operating Procedure - an established sequence of steps to be followed when operating a piece of equipment or a system
  • Overpressure - the pressure in a blast wave above atmospheric pressure
  • Oxidant - a chemical reagent that oxidizes another material (e.g., causes combustion of a fuel to occur)
  • Passive Ventilation - process by which the air in a room or building is supplied or removed by natural means (no mechanical devices). Passive (or natural) ventilation is effective because it takes advantage of buoyancy effects due to temperature or composition differences.
  • Personal Protective Equipment (PPE) - clothing and/or equipment designed to protect workers from workplace injuries (e.g., face shields, safety glasses, hard hats, safety shoes, goggles, coveralls, gloves, vests, earplugs, respirators)
  • Predictive Maintenance - an approach that determines when maintenance is needed based on the actual equipment condition and data on past performance
  • Pressure-Relief Device (PRD) - a safety device installed on tanks, pipes, and component systems to prevent damage due to overpressure
  • Preventive Maintenance - any planned maintenance designed to extend equipment life and avoid unscheduled maintenance outages. The goal is to prevent equipment failure rather than react to it.
  • Reactive Maintenance - the practice of waiting until an equipment failure occurs and then repairing the equipment
  • Reliability-Centered Maintenance - a systematic approach to evaluate a facility's equipment and develop a cost-effective approach to maintaining its reliability, by focusing attention on the higher-priority components first
  • Risk - the statisical chance of danger from an event; an evaluation of the severity and likelihood of an event
  • Safety Authority - a person or group of people recognized as safety experts in a particular field. The safety authority may be personnel appointed by your institution (e.g., a hydrogen safety committee) or they may be external consultants hired to review your safety plans.
  • Safety Culture - The assembly of characteristics and attitudes in organizations and individuals that establishes, as an overriding priority, that safety issues receive the attention warranted by their significance. It is the product of workers, managers, institutional values, attitudes, perceptions, competencies, and patterns of behavior that determine the commitment to, and the proficiency of, an organization's health and safety management.
  • Scheduling - deciding when the job will be done and which trained personnel will do it
  • Scope of Work - a series of actions or directions that accomplish a particular goal
  • Severity - the extent to which an event causes injury or damage
  • Standard Operating Procedure - an established sequence of steps to be followed when operating a piece of equipment or a system
  • Stop Work - provides workers the right, without reprisal, to decline to perform an assigned task because of a reasonable belief that the task poses an imminent danger or other hazard, coupled with a reasonable belief that there is insufficient time to seek effective redress through the normal reporting and abatement process. Establishes the authority and responsibility for workers to stop work when they discover that employees are exposed to conditions of imminent danger or to other hazards.
  • Stressors - parameters outside the design envelope (e.g., vibrations, friction, misalignment)
  • Subject Matter Expert - a group of Subject Matter Experts for work involving hydrogen may include: fire marshal, fire protection engineer, pressure safety engineer, explosive safety engineer, plant engineer, air quality engineer, electrical safety engineer, industrial hygienist, and ES&H coordinator
  • Tagout - placement of a prominent warning device (e.g., a tag) on an energy isolating device
  • Tangent - the straight unconvoluted portions at the end of the bellows
  • Tube Trailer - In the U.S., a truck-trailer chassis designed to transport large horizontal tubes of compressed hydrogen gas. In Europe, tube trailers can be designed for vertical cylinders.
  • Ullage Volume - space between the liquid level and the top of the vessel
Liquid Hydrogen Properties and Behaviors

Some basic properties and behaviors of liquid hydrogen are highlighted on this page. For more information on hydrogen properties, see Hydrogen Compared with Oth...

Some basic properties and behaviors of liquid hydrogen are highlighted on this page. For more information on hydrogen properties, see Hydrogen Compared with Other Fuels.

  • Hydrogen exists as a liquid at -423°F. Materials stored at this low temperature can cause cryogenic burns or lung damage, so personal protective equipment (PPE) is mandatory.
  • Hydrogen undergoes a rapid phase change from liquid to gas, so ventilation and pressure relief devices are built into cryogenic hydrogen systems to ensure safety.
  • The volume ratio of liquid to gas is 1:848. If you picture a gallon of liquid hydrogen, that same amount of hydrogen, existing as a gas, would, theoretically, occupy 848 gallon containers (without compression).
  • Even in dry climates, a liquid hydrogen spill will create a white cloud of condensed water vapor due to the cryogenic temperature affecting the humidity in the surrounding air. This low-temperature water vapor is heavier than air, so the cloud will remain localized and may move horizontally. As the hydrogen warms, it will dissipate and quickly rise.

Photo: Liquid Nitrogen Leak
A liquid hydrogen release will look similar to this liquid nitrogen release.
(Photo courtesy of Scott Stookey)

Hydrogen Applications

Industry has safely used hydrogen for decades in the following applications:

  • Petroleum refining
  • Glass purification
  • Semiconductor manufacturing
  • Aerospace applications
  • Fertilizer production
  • We...

Industry has safely used hydrogen for decades in the following applications:

  • Petroleum refining
  • Glass purification
  • Semiconductor manufacturing
  • Aerospace applications
  • Fertilizer production
  • Welding, annealing and heat-treating metals
  • Pharmaceuticals
  • As a coolant in power plant generators
  • For hydrogenation of unsaturated fatty acids in vegetable oil

Photo: Fuel Cell Diagram
(Photo courtesy of DOE)

New markets are emerging for industrial trucks (e.g., forklifts) and passenger cars powered by hydrogen fuel cells. Indoor and outdoor hydrogen fueling stations are being built in support of these vehicles. A fuel cell is a device that combines hydrogen with oxygen from the air in an electrochemical reaction to create electricity, which can power an electric motor and propel a vehicle. Fuel cells are twice as energy-efficient as combustion engines, and the hydrogen used to power them can come from a variety of sources, including renewable energy resources. A hydrogen fuel cell emits only heat and water, without producing any air pollutants or greenhouse gases.

PowerEdge C Series Forklift
PowerEdge C Series Forklift
(Photo courtesy of Nuvera Fuel Cells)

Private companies and government agencies (e.g., Department of Defense) with large warehouses/distribution centers are starting to adopt fuel cells to power their materials-handling equipment. Some of the companies that are deploying fuel cell industrial trucks are Walmart, Whole Foods, Bridgestone Firestone, Coca Cola, Central Grocers, Nestle Water, Fed Ex, and Genco. The hydrogen gas is stored outside and the dispensers for refueling the industrial trucks are located indoors.

Nine of the major auto manufacturers are developing fuel cell vehicles (FCVs) powered by gaseous hydrogen. There are approximately 300 FCVs on the road today, mostly in California, Michigan, Florida, and New York. There are about 60 outdoor hydrogen fueling stations in the U.S., with the majority of them located in Southern California. Some of the FCVs currently on the road are shown in the photos below.

Honda Carity FCX Toyota FCHV-adv Chevy Fuel Cell EV
Honda Clarity FCX
(Photo courtesy of DOE)
Toyota FCHV-adv
(Photo courtesy of Toyota)
Chevy Fuel Cell EV
(Photo courtesy of GM)

Stationary hydrogen fuel cells are used for:

  • Uninterruptible power supply for hospitals and data centers
  • Backup power for regional emergency shelters
  • Power for telecommunications in remote locations
Honda Carity FCX Toyota FCHV-adv Chevy Fuel Cell EV
Data Center Application
(Photo courtesy of Chevron Texaco)
Stationary Fuel Cell
(Photo courtesy of Plug Power)
Telecommunications Tower
(Photo courtesy of ReliOn)
Hydrogen Storage Systems

Gaseous Storage Systems

Cylinders - Hydrogen cylinders should be stored outside at a safe distance from structures, ventilation intakes, and vehicle routes, even while in use. Best practices call for compressed hydrogen b...

Gaseous Storage Systems

Cylinders - Hydrogen cylinders should be stored outside at a safe distance from structures, ventilation intakes, and vehicle routes, even while in use. Best practices call for compressed hydrogen bottles supplying a manifold to be located outside, with brazed/welded lines to connect to indoor equipment.

Cylinder Storage Photo
Outside Cylinder Storage
(Photo courtesy of PNNL)

Vessels - Storage vessels for compressed hydrogen gas should be designed, constructed, tested, and maintained in accordance with applicable codes and standards.

Liquid Storage Systems

Liquid hydrogen is usually stored in horizontal or vertical cylindrical tanks. Spherical tanks are sometimes used for larger volumes. Tanks are vacuum-insulated and contain redundant pressure-relief devices as a safety precaution to prevent over pressurization.

Hydrogen Storage Tank Photo
Liquid Hydrogen Storage Tank
(Photo courtesy of NREL)

Controls for Hydrogen Systems

Purging

  • One should always assume that hydrogen is present and verify that the system has been purged to the appropriate level when performing maintenance on a hydrogen system.
  • Likewise, one should always assume that air is p...

Purging

  • One should always assume that hydrogen is present and verify that the system has been purged to the appropriate level when performing maintenance on a hydrogen system.
  • Likewise, one should always assume that air is present and verify that the system has been purged to the appropriate level when reintroducing hydrogen into a system.

Pressure Relief System

  • Pressure equipment should be fitted with a pressure relief device (PRD), such as a rupture disc or a relief valve.
  • The PRD should be vented to a safe outside location.

Venting

  • Hydrogen storage facilities should be provided with adequate ventilation for both normal operating conditions and emergency situations.
  • Vent lines for hydrogen (including pressure relief lines and boil-off from cryogenic systems) should be vented to an appropriate exhaust system or a safe outside location.
  • The vent should be designed to prevent moisture or ice from accumulating in the line.
  • Unused hydrogen should be disposed of by venting or possibly flaring.
Hydrogen Hazards

This subsection contains information about hydrogen leaks, flames, and explosions. This information is not intended to dissuade you from working with hydrogen, but to make you aware that constant vigilance is necessary when working with or around...

This subsection contains information about hydrogen leaks, flames, and explosions. This information is not intended to dissuade you from working with hydrogen, but to make you aware that constant vigilance is necessary when working with or around hydrogen. In fact, hydrogen is just as safe as gasoline or any other commonly used fuel, it's just different. If you understand the differences, you will understand how to work safely with hydrogen.

Hydrogen Safety Panel

The Hydrogen Safety Panel was created to address concerns about hydrogen as a safe and sustainable energy carrier. Our principal objective is to promote the safe operation, handling, and use of hydrogen and hydrogen systems across all installations and applications. We believe this objective can be achieved through a variety of hydrogen safety efforts and activities, and that success will be measured by how effectively we are able to help:

  • identify and address safety-related technical data gaps
  • make design, construction, and operations personnel aware of relevant issues and best practices that affect safe operation and handling of hydrogen and related systems
  • convince design, construction, and operations personnel to give sufficient priority to safety in their daily, ongoing work.

The Hydrogen Safety Panel contributes to this objective by:

  • participating in safety reviews
  • providing safety planning guidance
  • reviewing project designs and safety plans
  • sharing safety knowledge and best practices
  • presenting and recognizing safety as a priority
  • participating in incident investigations.

The Panel’s approach is to focus on engagement, learning, and discussion rather than on audit or regulatory exercises, and to build on, rather than duplicate, the efforts of others such as the good work being done by codes and standards development organizations.

If you have interest in utilizing the expertise of the Panel, contact the program manager at 509-371-7894 or by email at hsp@h2tools.org

Compatibility of Materials

A Sandia National Laboratory Resource

Guidance on materials selection for hydrogen service is needed to support the deployment of hydrogen as a fuel as well as the development of codes and standards for stationary hydrogen use, hydrogen vehicles, refueling stations, and hydrogen transportation. Materials property measurement is needed on deformation, fracture and fatigue of metals in environments relevant to this hydrogen economy infrastructure. The identification of hydrogen-affected material properties such as strength, fracture resistance and fatigue resistance are high priorities to ensure the safe design of load-bearing structures.

To support the needs of the hydrogen community, Sandia National Laboratories is conducting an extensive review of reports and journal publications to gather existing materials data for inclusion in the Technical Reference for Hydrogen Compatibility of Materials. Additionally, Sandia is working internationally with collaborators to acquire newly generated data for inclusion in the Technical Reference. SAND2012-7321 is an archival report issued by Sandia National Laboratories representing the reference information compiled as of September 2012. Individual sections of this report may be updated or added periodically at this website.

Plain Carbon Ferritic Steels
Sub Metal Type Designation Nominal composition Revision Section
C-Mn Alloys
Fe–C–Mn
5/07
1100
Low-Alloy Ferritic Steels
Sub Metal Type Designation Nominal composition Revision Section
Quenched & Tempered Steels
Cr-Mo Alloys
Fe–Cr–Mo
12/05
1211
Quenched & Tempered Steels
Ni-Cr-Mo Alloys
Fe–Ni–Cr–Mo
12/05
1212
High-Alloy Ferritic Steels
Sub Metal Type Designation Nominal composition Revision Section
High-Strength Steels
9Ni-4Co
Fe–9Ni–4Co-0.20C
1/05
1401
Ferritic Stainless Steels
Fe–15Cr
10/06
1500
Duplex Stainless Steels
Fe–22Cr–5Ni+Mo
9/08
1600
Semi-Austenitic Stainless Steels
Fe–15Cr–7Ni
3/08
1700
Martensitic Stainless Steels
Precipitation-Strengthened
Fe–Cr–Ni
3/08
1810
Martensitic Stainless Steels
Heat Treatable
Fe–Cr
6/08
1820
Austenitic Steels
Sub Metal Type Designation Nominal composition Revision Section
300-Series Stainless Alloys
Type 304 & 304L
Fe–19Cr–10Ni
5/05
2101

Hydrogen Conversion Calculator

You may use this calculator to do simple conversions between four popular phase points of hydrogen

  • Liquid at boiling point (-252.87°C at 1 atm).
  • Gas at Normal Temperature and Pressure (NTP = 20°C at 1 atm).
  • Gas at standard conditions (15.6°C at 1 atm).
  • Gas at standard conditions (0°C at 1 atm).