10 Preliminary hazards analysis

A preliminary hazard analysis (PHA) is the first step in a formalized risk analysis or assessment. PHA is largely qualitative.

Additional lecture slides

Traditional Hazard Analysis

Example PHA for a warehouse

Sample PHA procedure

1. Identify resources to be protected: personnel, facilities, equipment environment
2. Identify and observe levels of acceptable risk that have been predetermined
3. Define the extent of the system to be assessed, including physical boundaries, operating phases.
4. Detect system hazards. Identify targets threatened by each hazard.
   1. Use engineering judgment
   2. Examine and inspect similar facilities or systems
   3. Examine system specifications
   4. Review codes and regulations
   5. Review safety studies based on relevant analogues
   6. Review relevant historical documents
   7. Consider external influences, such as weather, environment, personnel
   8. Consider all mission phases
   9. Consider common causes; i.e., common failure modes
   10. Consider all energy sources
5. Assess worst case scenario
   1. Severity of a hazard varies as a function of targets and operational modes
   2. Establish probability intervals
   3. The probability for a given hazard varies as a function of exposure time, target, population, operational modes
6. Assess risk for each hazard using a risk assessment matrix
7. Categorize each risk and develop countermeasures
8. Prioritize countermeasures
   1. Design change
   2. Engineered safety systems
   3. Safety devices
   4. Warning devices
   5. Procedures and training
9. Re evaluate the system with the new countermeasures installed.
10. 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

1. Crushing hazard
2. Shearing hazard
3. Cutting or severing hazard
4. Entangling hazard
5. Drawing-in or trapping hazard
6. Impact hazard
7. Stabbing or puncture hazard
8. Friction or abrasion hazard
9. High pressure fluid injection or ejection hazard

Electrical

1. Contact of persons with live parts (direct contact)
2. Contact of persons with parts which have become live under faulty
3. conditions (indirect contact)
4. Approach to live parts under high voltage
5. Electrostatic phenomena
6. Thermal radiation or other phenomena such as the projection of molden
   particles and chemical effects from short circuits, overloads, etc.

Thermal

1. 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
2. Damage to health by hot or cold working environment

Thermodynamic

1. Overpressure
2. Underpressure
3. Over-temperature
4. Under-temperature

Noise

1. Hearing loss (deafness), other physiological disorder (e.g., loss of balance,
   loss of awareness)
2. Interference with speech communication, acoustic signals, etc.

Vibration

1. Use of hand-held machines resulting in a variety of neurological and
   vascular disorders
2. Whole body vibration, particularly when combined with poor postures

Radiation

1. Low frequency, radio frequency radiation, micro waves
2. Infrared, visible and ultraviolet light
3. X and gamma rays
4. Alpha, beta rays, electron or ion beams, neutrons
5. “Sharks” with “lasers”

Materials/Substances

1. Hazards from contact with or inhalation of harmful fluids, gases, mists,
   fumes, and dusts
2. Fire or explosion hazard
3. Biological or microbiological (viral or bacterial) hazards

• Flammables (ignition, fire, explosion/detonation)
• Chemicals (toxicity, corrosion, off-specification)
• Pollutants (emissions, effluents, ventilation)

Environmental

1. Avalanche
2. Epidemic
3. Flooding
4. Freezing temperatures
5. Lightning
6. Seismic activity
7. Snow and ice
8. Storm
9. Volcanic eruption