Example IEC 61508 Safety Case: Learning from accident data


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Data on rebreather accidents is needed by all involved with rebreathers, for developing safety cases and for business assessment.

The database published here comprises 4 categories of information:

  1. Comprehensive database of fatal rebreather accidents.
  2. Tools and example data enabling the significance of accidents to be assessed statistically.
  3. Training Material on rebreather accident investigation and associated data.
  4. Summary of incidents and accidents for training purposes.

Please report any new accidents or serious incidents to the Coordinator at Deep Life

excelXLS


Rebreather Fatal Accident Database to 4th September 2014, with analysis (602KB)),

The public extract of the database of Rebreather Fatal Accidents and analysis, listing of 322 confirmed sports rebreather fatal accidents. Manufacturers can use this data to improve designs, instructors can use it to improve training, and divers can learn from it too. This list deviates from previous practice in that it contains names of all divers where these are in the public domain, to enable the accuracy of the list to be verified more easily. The main lessons for divers are:

BEFORE DIVING:
  1. Never go solo rebreather diving: on Open Circuit a diver generally knows immediately when a failure has occured - this is not the case on a rebreather - diving a rebreather without a buddy is extremely hazardous.
  2. Do all predive checks, and never dive a rebreather that you know to be faulty in any way.
  3. Check oxygen cells every 3 months with a cell checker, and look after them.
  4. Always follow your training: short cuts and ignorance kill.
  5. Always change your scrubber within the manufacturer's stated endurance for the dive profile you are diving with either a Micropore EAC, Draeger Divesorb or Molecular Products Sofnolime - do not use other scrubber materials, particularly do not use medical absorbant.
  6. Always replace your O2 cells after a year of service,or within 18 months after manufacture - whichever comes first.
  7. Always have eCCR electronics serviced annually even though manufacturers generally do not require this. Essential safety corrections are made during annual servicing.
WHEN DIVING:
  1. Pre-breathe for at least 3 minutes to check your PPO2 is under control
  2. Look at your PPO2 on entry,
  3. Look at your PPO2 at least every minute on initial descent,
  4. Look at your PPO2 at least every 4 minutes on the bottom,
  5. Look at your PPO2 continuously during ascent.
  6. !! Never ascend on a rebreather if you cannot see your PPO2. !!
  7. Always use rebreathers as pure oxygen units when near the surface.
  8. Always watch for CO2 problems: increasing breathing rate, fear or discomfort.
  9. !! When a diver aborts a dive, for any reason, the buddy MUST stay with him. It is the time when the diver will likely most need a buddy. Abandoning a diver aborting a dive may be manslaughter!!
IF REBREATHER SHOWS AN ALARM OR MALFUNCTIONS:
  1. Inject Make-up-gas (DIL) manually, then think.
    Hypoxia kills without warning, so flushing should be an automatic reaction drilled into you when a problem occurs. If you suspect hypercapnia (excess CO2) then bail out first, you will not be able to later.
  2. Do NOT ascend.
  3. Do NOT continue on RB without injecting gas manually.
  4. If in doubt, bail out. If you do not know your PPO2, then you must bail out immediately: your life depends on it.

excel


Risk Analysis Toolkit with Sports Rebreather Database. Updated to 9th May 08
The toolkit enables different types, models and versions of rebreather to be compared for safety based on observed accidents. The spreadsheet also provides tools for the assessment of rebreather accident risk and potential liability. Excel macros must be enabled to use this toolkit.

A database for the sports rebreather market is provided as an example, from which is calculated the global sports rebreather market size, revenue, accident risk and liability to net margin. The database is also used to illustrate how safety can be quantified, comparing the risk of using mCCR versus eCCR as one example and the changes to particular rebreather models as another. Changes may including training and use.

Note: Commercial, Military and Professional rebreathers have a much lower risk, and data on these is provided under Non-Disclosure to companies working with Deep Life Ltd.


acrobat reader

Rebreather Accident Analysis: a short tutorial guide (59KB)
A short tutorial guide on the main steps in investigating a rebreather accident, for use as forensic training material.


Effect of water ingress on the breathing resistance of scrubbers using granular CO2 absorber (175KB)
Forensic report on the effect of water ingress on breathing resistance in a typical granular scrubber. Report enables packing to be assessed in rebreathers recovered after an accident where the equipment is flooded.

acrobat reader

How Rebreathers Kill People (68KB)
Incident reports showing some of the critical failures in rebreather design, and the actions that need to be taken to address them.