Confined Space Operations Training
AIRCRAFT FUEL CELL ENTRY SAFETY
Presentation Outline • • • • • • •
Introduction Hazard Assessment Ventilation Air Monitoring PPE Entry Team Roles Communication
• Tools and Equipment • Training • Emergency Response • Entry Permit and Checklist
I.
Introduction: What and where are aircraft fuel cells?
Introduction: Fuel Cell Structure • Usually located within wings • Complex internal architecture • Small access doors
Introduction: Who enters aircraft fuel cells, and why? • Airplane manufacturing workers, for: – Assembling structure – Sealing – Coating – Installing components
• Airplane maintenance workers, for: – Inspection, maintenance, and repair of above
Introduction: Applicability Not covered in this presentation: • Aircraft using other than commercial jet fuel • Bladder or foamed fuel cells • Assembly of new aircraft • Entry into other spaces on airplanes • Entry not aboard airplanes • Flight safety issues
II. Hazard Assessment • • • • • •
Physical Safety Hazards Ergonomic Hazards Jet Fuel Flammability Hazards Jet Fuel Exposure Hazards Other Atmospheric Hazards Miscellaneous Hazards
Physical Safety Hazards
• Difficult Entry/Exit • Working at Heights • Low Head Clearance • Entanglement • Moving airplane components • Moving airplanes
Ergonomic Hazards
• Awkward postures • Limited mobility • Resting on uneven surfaces • Repetitive motions • Vibration
Jet Fuel Hazards: Composition of Jet Fuel A • Mixture of middle range petroleum distillates (C9-16) similar to kerosene • May include varying low levels of other more complex petroleum hydrocarbons • Additives: Antioxidants, metal deactivators, corrosion inhibitors, static dissipaters, thermal stabilizers, biocides, and fuel system icing inhibitors • Other jet fuels: JP-4, JP-5, and JP-8
Jet A Hazards: Flammability Combustibility Parameters
(too rich to burn) 4.7%
Upper Explosive Limit
47000 ppm
LEL: 0.6% EXPLOSIVE RANGE
UEL: 4.7% Vapor Pressure: <5 mm Hg Flash Point:
100-106oF
0.6%
Lower Explosive Limit
6000 ppm
(too lean to burn) 0%
0 ppm
Explosive Range Concentrations for Jet Fuel Vapor in Air at Ambient Temperature and Pressure
Jet A Hazards: Short-Term Toxicity • Skin Contact: Drying and irritation • Eye Contact: Moderate irritation • Inhalation: – Respiratory irritation – Short-term central nervous system effects such as headache, dizziness, nausea, impaired coordination, and fatigue – Inhalation of high concentrations of vapor or aerosol may lead to chemical pneumonitis, a lung condition similar to pneumonia
Jet A Hazards: Long-Term Toxicity • Solvent dermatitis • Other systemic effects have been and still are under study: – Nervous system effects – Immune system effects – Respiratory system effects – Liver and kidney effects – Reproductive system effects
Jet A Hazards: Exposure Limits
• No single consensus standard at this time • Options include: – ACGIH TLV for Jet Fuels/Kerosene = 28.6 ppm – NRC, USN, USAF for Jet Fuel = 52 ppm – OSHA PEL for Stoddard Solvent = 500 ppm (all are 8-hour TWA)
• Check with your local occupational safety and health jurisdiction for an appropriate worker exposure limit concentration for jet fuel
The New ACGIH TLV: Kerosene/Jet Fuels • 200 mg/m3, 8 hr TWA (~28.6 ppm) • As total hydrocarbon vapor • Skin notation • A3 Confirmed animal carcinogen • “based on the vapor inhalation studies with rodents”
Other Atmospheric Hazards: Oxygen •
•
•
Oxygen Deficiency – Asphyxiation hazard – Causes: Introduction of inert gases, entrant’s respiration – Lower safety limit typically 19.5% Oxygen Enrichment – Fire Hazard – Upper safety limit typically 23.5% Investigate any variation from ambient
Other Atmospheric Hazards: Hazardous Material Usage • Used inside: – Solvents -Sealants – Coatings -Test agents – Particulate from sanding, grinding, etc.
• Used outside: – Same classes of products as above – Vehicle exhaust – Introduced by ventilation system
Other Hazards: Ignition Sources • Airplane electrical components – In tank
-Outside
• Electrical equipment taken inside – Lighting
-Tools and test eqpt.
• Static discharge – Tools and textiles -Grounding
• Hot work
Other Hazards: Physical Exposures
• • • •
Noise Heat and cold Radiation High or low air pressure
Other Hazards: Entrant Factors to Consider • Physical size • Claustrophobia • Certain health conditions, due to: – Difficulty of rescue – Potential for chemical exposure – Ergonomic stresses
• Employees who regularly perform fuel cell work should receive pre-assignment and periodic health evaluations.
III. Ventilation • • • • • •
Supply vs Exhaust Types of Air Movers Selecting Air Movers Ducts Pre-Entry Ventilation During-Entry Ventilation Set-Up
Ventilation: Supply vs. Exhaust Exhaust Ventilation Fuel Cell
Exhaust Air to
Exhaust Duct
Wing Opening to Air Duct Adapter Passive Air Flow into Wing
Air Mover
Supply Ventilation Fuel Cell
Passive Air Flow out of Wing
Wing Opening to Air Duct Adapter
Supply Duct
Supply Air from Air Mover
Push-Pull Ventilation Fuel Cell
Exhaust Air to
Exhaust Duct
Wing Opening to Air Duct Adapters
Supply Duct
Air Mover
Supply Air from Air Mover
Figure 7: Types of Fuel Cell Ventilation
Ventilation: Air Mover Types Blowers and Venturis
Ventilation: Air Mover Selection Criteria • • • • • • •
Flow Rate Static Pressure Explosion Proof Power requirements Heating/Cooling Portability Physical Size
Ventilation: Flexible Ductwork • • • • • •
Helical vs Collapsible Conductivity Flexibility Length Diameter Inspection
Ventilation: Pre-Entry vs. During-Entry • Pre-Entry – Starts when tank is opened – Ventilates entire tank – Helps evaporate residual fuel – Dilutes fuel vapor concentration to safe entry levels – Venturis often used to exhaust
• During-Entry – Focused at entrant’s location – Must dilute vapors from solvents or paints – Blowers often used to supply air or as part of push-pull system
Ventilation Configuration
8-Inch Duct
Air Blower
Air Blower
A ir B lo w e r
8 -In c h D u c t
Open Access Door Closed Access Door Worker in Tank Wing Opening Adapter
8-Inch Duct
IV. Air Monitoring • Instrument types • Instrument criteria • Pre-Entry vs DuringEntry • Procedure • Oxygen • LEL • ppm fuel vapor • Other contaminants
Air Monitoring: Instrument Types • Combustible Gas Indicator (CGI) – OK for LEL – Use conversion for jet fuel
• Photoionization Detector (PID) – Accurate for ppm – Can direct-read jet fuel
Monitoring Instrument Criteria • • • • • • • •
Oxygen at 0.1% LEL At 1% ppm at 10 (if used) Real time Easy to read Adjustable Alarms Explosion proof Portable
• • • • • • • •
Rugged Fuel Resistant Pump and probe 8-hour battery Easily Calibrated Conversion factors Temp and pressure Radio shielded
Monitoring: Pre-Entry vs. During-Entry • Pre-Entry
• During-Entry
– Done from outside – Measures O2 & fuel vapor concentration – Check representative areas as accessible – Ascertains if it is safe to enter – Determines respiratory protection
– Done from inside or outside – Sampled at representative locations – Must measure fuel, O2, and any other hazards – Verifies that conditions remain safe – Frequency varies per changeability of hazard
General Monitoring Procedure
• Check battery • Calibrate (CalCert once per year) • Check/record/program conversions • Set alarms as appropriate • Measure in order: O2, LEL, ppm • Measure appropriate areas
Monitoring: Interpreting Results • Oxygen – Consider reduced pressure effects – Investigate any variation from ambient
• LEL – Alarm at 10%
• PPM – Alarm if Exposure Limit exceeded
• Other Contaminants – Use appropriate conversion – Consider mixtures
V. Personal Protective Equipment • Hand Protection • Coveralls • Eye Protection • Ear Protection • Respirators
PPE: Gloves • • • • • • •
Nitrile effective for jet fuel Select specific for other materials Breakthrough time Thickness Flexibility Dexterity Durability
PPE: Coveralls, etc • • • • • •
De-puddle tank prior to entry Cotton coveralls usually worn Static-free Use other materials for specific hazard Heat stress Hats and booties
PPE: Eye and Ear Protection • Safety Glasses with side shields for most jobs • Chemical splash goggles or full facepiece respirators for certain jobs • Ear protection for riveting, ventilation • Plugs preferable to muffs
PPE: Respirator Selection • • • •
Use organic vapor cartridge respirator Do not exceed LEL Half-mask vs full facepiece Air purifying vs air supplying
PPE: Air Purifying Respirators • OV cartridge for fuel, solvents • OV/P100 for spray paint, particulates • Limited use life • Not for IDLH or low O2 • Usually preferred by entrants
PPE: Air Supplying Respirators • Highest protection factors • Needs Grade D air source • Can provide cooling, avoid fogging • Loose fitting hood only option for beards
VI. Entry Team Roles
• Entrant • Attendant • Detector Operator (usually the attendant)
• Authorizer (usually team leader)
• Emergency Responder
Roles: Entrant • • • • •
Enters! Wears required PPE Employs safe work practices Communicates with attendant Evacuates if unsafe conditions or symptoms occur
Roles: Attendant • • • •
Monitors well being of entrant Watches for unsafe conditions outside Prevents unauthorized entry Directs exit if unsafe conditions or symptoms occur • Summons emergency services • Never enters the space • Usually operates the detector
Roles: Authorizer • Takes overall responsibility for entry • Verifies that all safe entry requirements are met • Signs permit and checklist • Usually supervisors, leads, or other specifically identified experienced employees • May also serve as attendant or detector operator
Other Roles • Detector Operator • Emergency Responder
VII. Communication • Constant capability • Initiated by either entrant or attendant • Types: – – – – –
Voice Other sound Visual Tactile Electronic • Hard wired • Wireless
VIII. Tools and Equipment
• • • • •
Signage Locks & Blocks Hand tools Wipers/Brushes Waste Containers
Tools and Equipment (cont.)
• • • •
Lifts Entry Stands Ladders Combinations
Tools and Equipment (cont.)
• Lighting • Electrical equipment • Pneumatic equipment • FOD control
Tools and Equipment (cont.) • Prohibited: – smoking materials, matches, lighters – food or drinks – chewing tobacco – metal buttons or belt buckles – loose fitting jewelry – watches, pagers – portable telephones and radios (except communication radios as required)
IX. Training
• • • •
Who What When How
Training: Who
• • • • •
Entrants Attendants Authorizers Detector Operators Emergency Responders
Training: What • Definitions • Hazards • Signs of entrant distress • Entrant self rescue • Roles and responsibilities • Communication
• Atmospheric monitoring • Ventilation • PPE • Tools & Equipment • Emergencies • Permits and logging
Training: When • Initial – Prior to assignment
• Refresher – At set intervals, i.e. annual
• Remedial – When inadequate knowledge is demonstrated
Other Required Training • • • • • • •
Hazard Communication Respiratory Protection Control of Hazardous Energy Sources Hearing Conservation Use of PPE Fall Protection Aircraft Process Certifications
X. Emergency Response • • • • • •
In-house vs local jurisdiction Advance planning Qualifications of responders Summoning of emergency services Emergency priorities Practice
Emergency Equipment
• Self Contained Breathing Apparatus • Extrication tools • Life support equipment • Firefighting equipment
XI. Entry Permit & Checklist • Purpose – Systematic checklist – Designates roles – Provides documentation
• Appendices – Entry log – Air monitoring data
• Posting • Retention