10 Preliminary hazards analysis
A preliminary hazard analysis (PHA) is the first step in a formalized risk analysis or assessment. PHA is largely qualitative.
Sample PHA procedure
- Identify resources to be protected: personnel, facilities, equipment environment
- Identify and observe levels of acceptable risk that have been predetermined
- Define the extent of the system to be assessed, including physical boundaries, operating phases.
- Detect system hazards. Identify targets threatened by each hazard.
- Use engineering judgment
- Examine and inspect similar facilities or systems
- Examine system specifications
- Review codes and regulations
- Review safety studies based on relevant analogues
- Review relevant historical documents
- Consider external influences, such as weather, environment, personnel
- Consider all mission phases
- Consider common causes; i.e., common failure modes
- Consider all energy sources
- Assess worst case scenario
- Severity of a hazard varies as a function of targets and operational modes
- Establish probability intervals
- The probability for a given hazard varies as a function of exposure time, target, population, operational modes
- Assess risk for each hazard using a risk assessment matrix
- Categorize each risk and develop countermeasures
- Prioritize countermeasures
- Design change
- Engineered safety systems
- Safety devices
- Warning devices
- Procedures and training
- Re evaluate the system with the new countermeasures installed.
- Determine if countermeasures introduce new hazards or diminish system performance.
Hazard Checklist
Mechanical
Properties of machine parts or workpieces
- Shape
- Relative location
- Mass and stability (potential/kinetic energy)
- Inadequacy of mechanical strength
Accumulation of energy inside the equipment
- Elastic elements (springs)
- Liquids and gases under pressure
- The effects of vacuum
- Crushing hazard
- Shearing hazard
- Cutting or severing hazard
- Entangling hazard
- Drawing-in or trapping hazard
- Impact hazard
- Stabbing or puncture hazard
- Friction or abrasion hazard
- High pressure fluid injection or ejection hazard
Electrical
- Contact of persons with live parts (direct contact)
- Contact of persons with parts which have become live under faulty
- conditions (indirect contact)
- Approach to live parts under high voltage
- Electrostatic phenomena
- Thermal radiation or other phenomena such as the projection of molden
particles and chemical effects from short circuits, overloads, etc.
Thermal
- Burns, scalds and other injuries by a possible contact of persons with
objects or materials with an extreme high or low temperature, by flames or
explosions and also by radiation of heat sources - Damage to health by hot or cold working environment
Thermodynamic
- Overpressure
- Underpressure
- Over-temperature
- Under-temperature
Noise
- Hearing loss (deafness), other physiological disorder (e.g., loss of balance,
loss of awareness) - Interference with speech communication, acoustic signals, etc.
Vibration
- Use of hand-held machines resulting in a variety of neurological and
vascular disorders - Whole body vibration, particularly when combined with poor postures
Radiation
- Low frequency, radio frequency radiation, micro waves
- Infrared, visible and ultraviolet light
- X and gamma rays
- Alpha, beta rays, electron or ion beams, neutrons
- “Sharks” with “lasers”
Materials/Substances
- Hazards from contact with or inhalation of harmful fluids, gases, mists,
fumes, and dusts - Fire or explosion hazard
- Biological or microbiological (viral or bacterial) hazards
- Flammables (ignition, fire, explosion/detonation)
- Chemicals (toxicity, corrosion, off-specification)
- Pollutants (emissions, effluents, ventilation)
Environmental
- Avalanche
- Epidemic
- Flooding
- Freezing temperatures
- Lightning
- Seismic activity
- Snow and ice
- Storm
- Volcanic eruption