Hydrogen Safety Lecture Notes PDF

Okay, here's the conversion of the images into a structured markdown format, as requested. ### Lecture 18. Hydrogen Safety * Properties of Hydrogen * Hydrogen Hazards & Prevention * Hydrogen Facility Related Safety ### Hindenburg Disaster The infamous Hindenburg disaster (May 6, 1937) *...

Okay, here's the conversion of the images into a structured markdown format, as requested. ### Lecture 18. Hydrogen Safety * Properties of Hydrogen * Hydrogen Hazards & Prevention * Hydrogen Facility Related Safety ### Hindenburg Disaster The infamous Hindenburg disaster (May 6, 1937) * $H_2$ is a very unique gaseous element * $H_2$ leaks fast through small orifices * It is highly volatile and flammable * It is labeled as a dangerous substance * The Hindenburg disaster ended its application in transportation * 37 Casualties, 2/3 on board survived * The fire did not start with $H_2$, but with the flammable skin of the airship * It was the propulsion fuel (diesel fuel), not $H_2$, that made the most damage ### HYDROGEN HAZARDS? A Hazard: Event or Condition that Can Result in Exposure to Harm or Loss. * The Primary Issues For Hydrogen Are: * Combustion Hazards * Pressure Hazards * Low Temperature Hazards * Hydrogen Embrittlement Hazards * Health Hazards ### HYDROGEN PROPERTIES * **General Properties** * $GH_2$: Flammable, Nontoxic, Noncorrosive * Asphyxiant, Colorless, Odorless, Tasteless * Lightest Gas (15x less dense than air) * $LH_2$: Noncorrosive, Colorless Liquid * **Physical Properties** * Several Isotopes and Molecular Forms * Physical Forms Considered for Storage: Gas, Liquid, and Slush * **Cryogenic Properties** * NBP 20.3 K * $LH_2$: Condenses/Freezes all Gases Except He * Liquid Density: 14x less dense than water * Liquid Thermal Expansion: 23.4x of water * Gas Above Critical Temperature (33 K) ### SAFETY RELATED PROPERTIES * Equivalent Gas Volume Factor 845.1 times (@ NTP for NBP Liquid) * Pressure (Liquid expansion in a fixed volume) 172 MPa * Small Molecular Size 1.8 angstroms * Passes Through Openings too Small for Helium * Low Viscosity * Through Porous Materials * Penetrates Softgoods * Penetrates Intermolecular Spaces and Grain Boundaries in Metals * High Diffusivity \[Diffusion Coefficient - 0.061 $cm^2$/s in NPT air] * High Buoyancy \[up to 9 m/s]/Promotes Forced Convection * Flame is Invisible in Ambient Light/Produces Little IR * Unless Impurities are Present \[Carbon, Sodium give Color] ### HOW TO ADDRESS HAZARDS GENERAL STRATEGIES * Work to Minimize Severity * Minimize Quantities to Only What's Needed * Apply Area Control, PPE, & Good Housekeeping * Use Detectors, Warning Devices * Follow Operational Requirements * Use Safe, Proven, Principles & Practices * Prevent Fuel-air Mixtures, Remove sources of ignition * Use Defensive Practice * Use Situational Awareness * Control Through Organizational Policies & Procedures * Use Approved Procedures & Checklists * Review (Design, Safety, Hazards, Operations) * Follow Approved Maintenance & Quality Control Programs ### Detailed Hydrogen Hazards Analysis Process The image shows a flowchart. The process begins with defining the scope of analysis and selecting team members. The next step is compiling component/system information. After this, a decision is made on the component analysis strategy, which is followed by determining component hazards scenarios. The process then branches into two parallel lines of analyses: 1. Component by Component: * Assess possible combustible mixture formation * Assess possible ignition mechanisms * Assess possible combustion mechanisms (Fire, Deflagration, Detonation) * Analyze possible secondary effects * Assess Reaction Effects 2. Team analysis The processes converge at "Complete Report" | Component/ Operational Mode | Failure Modes | Flammable Mixture Formation | Ignition | Fire Deflagration Detonation | Secondary Effects | Overall Effects | | -------------------------------------------: | :------------ | :--------------------------- | :------- | :----------------------------- | :---------------- | :-------------- | | Valve # --- Rating | 0-4 | 0-4 | 0-4 | 0-4 | N/R | A-D | ### Combustion Hazards * Combustion: Fire, Deflagration, Detonation * Requires Mixing with an Oxidizer * Basic Combustion Properties * Flammability Limits In NTP Air 3.9 - 75.0 vol % * Flammability Limits In NTP Oxygen 3.9 - 95.8 vol % * Detonability Limits In NTP Air 18.3 - 59.0 vol % * Detonability Limits In NTP Oxygen 15 - 90 vol % * Minimum Ignition Energy in Air 0.017 mJ * Autoignition Temperature 858 K (1085°F) * Quenching Gap In NTP Air 0.064 cm * Flame Velocity 2.70 m/s (8.9 ft/s) * Flame Emissivity 0.10 ### Combustion Hazards The image is a bar graph that shows the flammable range of air for Methane, Propane and Hydrogen. * Methane's flammable region goes from 5 to 17. * Propane's flammable region goes from 2.1 to 9.5. * Hydrogen's flammable region goes from 4 to 75 ### Combustion Hazards Comparison of Properties Commonly Used Fuel Gases | | Hydrogen | Methane | Propane | | :--------------------------------- | :------- | :------ | :------ | | Density, kg $m^{-3}$ at NTP | 0.084 | 0.65 | 2.01 | | Ignition limits in air, volume% at NTP | 4.0 to 77| 4.4 to 16.5 | 1.7 to 10.9 | | Ignition temperature, °C | 560 | 540 | 487 | | Min. ignition energy in air, MJ | 0.02 | 0.3 | 0.26 | | Max. combustion rate in air, $ms^{-1}$ | 3.46 | 0.43 | 0.47 | | Detonation limits in air, volume% | 18 to 59 |6.3 to 14 | 1.1 to 1.3 | | Stoichiometric ratio in air | 29.5 | 9.5 | 4.0 | Conclusion: All things considered, $H_2$ is no more dangerous, and in some respects it is rather less dangerous than other commonly used fuels. $H_2$ has a wide range for detonation, its flame is invisible, but its lowest density makes it dissipate very fast. ### BASIC COMBUSTION PRACTICE The image displayed a fire triangle: * The fire triangle is labelled "Fire Tangle" * The sides are labelled FUEL, OXYGEN, and IGNITION, and are coloured red. * Fuel side is referred to Hydrogen * Oxygen side is referred to Oxygen/Air * Ignition side leads to circle containing: * Electric Spark * Electric Arc * Heat ### Combustion Hazards Prevent formation of a combustible mixture * Prevent leaks and spills of $H_2$ from a $H_2$ system * Keep external air from entering a $H_2$ system * Prevent $H_2$ or air from leaking from one part of a system into another part * Prevent contamination from entering a $H_2$ system with * the $H_2$ * a pressurization gas ### Combustion Hazards Prevent formation of a combustible mixture * Avoid contaminating a H₂ system by * an insufficient purge process * a contaminated purge gas * Purge air from a H₂ system prior to introducing H₂ into the system * Purge H₂ from a H₂ system prior to introducing air into the system * Maintain adequate ventilation * Use proper materials ### Combustion Hazards Eliminate ignition sources * Electrical (e.g. static, sparks, lightning) * Mechanical (e.g. friction, galling, fracture) * Thermal (e.g. match, cigarette, welding) * Chemical (e.g. catalysts, reactants) ### Pressure Hazards Potential exists for creation of extremely high pressure in a closed volume * Equivalent volume gas @ NTP/volume liquid @NBP = 845 * Pressure to maintain NBP liquid density in NTP gas = 172 MPa (24,946 psi) * Heat of vaporization = 445.6 J/g (small heat input will vaporize LH₂) ### Pressure Hazards * Pressure relief devices must be used in any volume in which $LH_2$ or cold $H_2$ gas can be trapped * Cryopumping can create subatmospheric pressure ### Pressure Hazards * Pressure Hazards Arise from the Need to Concentrate Hydrogen * Significant Stored Energy (Cryogenic or High Pressure) * Overpressure, Shockwaves, and Shrapnel, when Suddenly Released * Possible Causes * Liquid to Gas Phase Change * Overfilling * Pressurization System Failure, Relief System Failure, or Inadequate Venting * Fire or Overheating from an External Source ### Low Temperature Hazards $LH_2$ will solidify any gas except He (NBP $H_2$ = 20.3 K; NBP He = 4.2 K) * Contaminant solidification * Liquid air can form on uninsulated surfaces (oxygen enriched to ~50%) * Liquid air can be trapped in foam insulation (within gaps and within foam cells) ### Low Temperature Hazards * Low temperature embrittlement of containment materials and nearby materials * Use appropriate materials * Contact with a cold surface can result in cryogenic burn (frostbite) * Insulate cold surfaces * Use appropriate personal protective equipment ### Low Temperature Hazards * Dimensional changes because of contraction * For temperature change from 300 K to 20 K: * Stainless steel will contract ~ 0.3% * PTFE will contract ~ 2.1% * Many plastics become extremely brittle, even cracking when cooled to 20 K * Such materials cannot be used for seals, valve seats, etc. ### Embrittlement Hazards * $H_2$ Dissociates and Atomic Hydrogen Penetrates Metals Causing a Decrease in Material Strength * Mechanical properties can be significantly reduced * Tensile strength * Ductility * Fracture toughness * Crack behavior * Failures have occurred unexpectedly ### Embrittlement Hazards H2 embrittlement commonly addressed by: * Material selection * Conservative design stress (avoid yielding) * Increased material thickness * Welding technique * Surface finish ### Embrittlement Hazards Examples of material susceptibility: * Extremely embrittled * 410 SS, 1042 steel, 17-7 PH SS, 4140, 440C * Severely embrittled * AISI 1020, 430F, Ti-6Al-4V * Slightly embrittled * 304 ELC SS, 305 SS, Be-Cu alloy 25, Titanium * Negligible embrittled * 310 SS, 316 SS, 1100 Al, 6061-T6 Al, OFHC copper ### Health Hazards * Fire burn * Direct contact with flame * Thermal energy radiated from flame * UV exposure * Cryogenic burn (frostbite) * Asphyxiation * Hydrogen * Purge gas (He, N₂) * Hypothermia ### Health Hazards * Exposure to Flame * Direct Contact with Flame (2nd Degree Thermal Burns → image of burn) * Thermal Energy Radiated from Flame (Flash burn) * UV Exposure * Cryogenic Burn (Frostbite) (3rd Degree Cryogenic Burns → image of frostbite) * Hypothermia * Asphyxiation * Hydrogen * Purge Gas (N2, He) * Overpressure → | Maximum Overpressure (kPa) | (psi) | Effect On Personnel | | :------------------------- | :---- | :-------------------- | | 7 | 1 | Knock Personnel Down | | 35 | 5 | Eardrum Damage | | 100 | 15 | Lung Damage | | 240 | 35 | Threshold For Fatalities | | 345 | 50 | 50% Fatalities | | 450 | 65 | 99% Fatalities | ### H2 COMBUSTION ANALYSIS LEMENTS * Anticipate Failures that Result in Hydrogen Release * Know What Mixtures can Form and Under What Conditions * Be Aware of the Effects of Confinement * Identify Potential Ignition Sources * Understand Combustion Modes: Fire, Deflagration, & Detonation ### H2 COMPONENTS ---- GENERAL * Joints, Connections, Valves, Pressure Relief Devices, Filters, Thermal Insulation, Vacuum Subsystems, Detectors, etc... * Components, including softgoods, must be compatible with the operating conditions * Materials of Construction Must be Compatible with Hydrogen * Dimensional Changes Must Be Accounted for Where Large Temperature Gradients Occur * Where Appropriate, Energized Components Must be Compatible with Flammable Atmospheres * Volumes that Contain Hydrogen Shall have Adequate Instrumentation and Controls to Ensure that Operation is within Acceptable Limits ### HYDROGEN COMPONENTS * Joints and Connections * Welding Recommended, Soft-Solder Not Permitted * Threaded with Sealant Ok for GH2, not LH2 * Bayonet Connections used with LH2 * Under 2" OD Flared, Flareless, and Compression Joints Ok * Use Demountable Joints Only When Necessary * Valves should have provisions to prevent trapping LH2 * Relief Devices * Required for Cryogenic Systems * Redundancy & Redundancy in Types Commonly Required * Limit Pressures to MAWP and Size for Adequate Flow Capacity * Output Should not Impinge on Adjacent Components or Personnel and Should not be Restricted or Impeded * Are Required on Lower Pressure Regions and Vacuum Volumes ### FACILITY SUBSYSTEMS CONSIDERATIONS * Storage Systems - Sited per 29CFR, Designed ASME BCPV or DOT regulations * Piping - Designed, Fabricated, & Tested per ASME B31.3 * Venting, Flaring, and Dispersion: CGA G-5.5 * Air and Precipitation Shall be Prevented from Entering a Vent System * Vents Should be Located to Prevent Hydrogen from Impinging on Ventilation Ducts or Other Equipment * Flaring Typically Used for Quantities > 0.5 lb/sec * Disposal Factors Include: Quantity & Extent of Combustible Cloud, Thermal Radiation Hazards, Surrounding Site Conditions ### FACILITY SUBSYSTEMS CONSIDERATIONS * Buildings - Designed to Minimize Injury & Damage in Event of a Fire or Explosion (See 29CFR 1910.103) * Avoid Collection Points, Maintain Adequate Ventilation * Provide Explosion Venting, 2 Hour Fire Resistance Rating * Inert Gas Subsystems - Consider Positive Means of Shutoff ### FACILITY SUBSYSTEMS CONSIDERATIONS * Fire Protection Subsystems: Include Automatic Shutdown, Sprinklers, Deluge systems, Water Spray Systems ### FACILITY SUBSYSTEMS CONSIDERATIONS * Electrical Support Equipment Considerations * Explosion Proof or Purged Equipment * Bonded and Grounded * Lightening Protection * Provide Adequate Illumination * Transportation - per 49CFR ### $LH_2$ Transfer Operations * Transfer via * Pump * Pressure differential * Maintain flow rate within minimum and maximum limits * Cooldown process must be controlled * Prevent over-stressing * Eliminate pipeline bowing ### HYDROGEN SAFETY SUMMARY * Hydrogen Use is Important, but There are Hazards/Risks * A Core Body of Knowledge Exists and Hydrogen can be Used Successfully * Hydrogen can be Used Safely by Thinking, Planning, Training, and Being Prepared * Use Conservative Approach * Recognize Hazards and Limitations * Search for Hazards * Don't take chances or shortcuts