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The Diving Seminar Bergen, 2007 Standards Requirements for Rebreathers. Dr. Alex Deas, PhD, FIEE. Importance of safety standards. More than 150 sports divers have died on rebreathers ‡ 32 due to natural causes, marine life and general diving hazards

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Importance of safety standards

  • More than 150 sports divers have died on rebreathers ‡
  • 32 due to natural causes, marine life and general diving hazards
  • Remainder (118) died because the rebreather failed to:
    • Keep the oxygen levels (PPO2) within set limits
    • Keep the diver’s carbon dioxide levels within set limits
    • Keep the water out
  • None of those (118) deaths would have occurred if the rebreather concerned met just two of the safety standards (EN14143/U101 + EN61508) Ignorance by manufacturer of how to do it properly + attitude of “How do we avoid doing what the standard requires?”
  • The three rebreathers that are closest to meeting the safety standards have had no fatal accidents

‡From the Central Database of Rebreather fatalities, public extract of which is on and http://www.rebreatherworld.comNote: 26 of the 150 accidents have scant data, so are assigned in the same proportion as the accidents for which there is sufficient data to identify root cause.


Regulations affecting rebreathers

  • EEC Personal Protection Equipment (PPE) Directive, 89/686/EEC
  • EN14143:2003 Diving Rebreathers . Harmonised PPE Standard
  • EN61508:2004 Safety of Electrical & Programmed Systems
  • Restriction of Hazardous Substances Directive (RoHS) 2002/95/EC
  • EEC EMC Directive 2004/108/EC
  • EEC Low Voltage Directive (LVD) 2006/95/EC
  • EEC Machinery Directive 98/37/EC and Directive 2006/42/EC
  • NORSOK U-100 2006 Manned Underwater Operations
  • NORSOK U-101 1999 & 2007 update. Diving Respiratory Equipment
  • NORSOK S-002 Safety at Work
  • NORSOK S-005 Machinery Working Environment
  • DNV-OS-E402 2004 Offshore Standard for Diving Systems
  • IMCA AODC 035 (Electrical), plus DO12 (SS in O2), plus D001 (Battery housings)
  • OSHA 29 CFR Part 1910 Subpart T: Commercial Diving Operations
  • + 25 others.

Two different classes of standards

  • Both types of standards have the same motive:
    • To ensure risks are reduced to acceptable levels
  • Some define safety by setting the performance required:
    • EN14143:2003 Rebreather Diving Equipment
    • NORSOK U101:1999 Rebreather Diving Equipment
    • IMCA AODCs, e.g. AODC 35 for electrical safety underwater
  • Some define safety by setting the safety objective:
    • EN61508:2004 Safety of Electrical and Programmed Systems
    • CE PPE Directive: Personal Protective Equipment Directive 89/686/EEC
    • Norwegian Safety at Work Regulations

Performance type standards

  • EN14143 and NORSOK U101 are very similar in coverage
  • U101 considers deeper diving than EN14143 and is more stringent (requires many more data points at all depths, and generally higher performance).
  • These standards set limits for characteristics such as:
    • Work of Breathing (must not be worse than Open Circuit SCUBA)
    • Scrubber Endurance
    • Hydrostatic Imbalance
    • PPO2 Control
    • CO2 Monitor Accuracy
    • Gas temperatures
    • Breathing hose mechanical strength
  • These tests are things any competent company would measure anyway when developing a new rebreather.

Safety by objective

  • The CE PPE Directive requires the manufacture to prove the equipment is safe and fit for purpose.
  • Compliance with a Harmonised Standard is deemed to meet PPE Compliance
  • EN14143 is the CE Harmonised Standard for rebreathers and sets minimum performance levels
  • EN14143 requires compliance with EN61508
  • EN61508 is a completely different category of safety standard to EN14143: it does not consider performance, but the Safety Integrity Level (SIL) that is required by the application.
  • EN61508 is very much more onerous than any other standard.

EN61508: Onerous & Pervasive

  • As soon as any safety system has any programmed, electrical or electronic element, then EN61508 is invoked.
  • When EN61508 is invoked, it applies to the WHOLE system not just to the electronics because it has end-to-end scope.
  • That means the scrubber, the plastics (off-gasing), hoses, ergonomics: everything is covered.
  • This means that mechanical parts need HAZOPs, & safety studies that would not be demanded if there is no programmed, electrical or electronic element.

Applying EN61508 to a rebreather

  • StatoilHydro-Technip Personal Diving Equipment Project is the first commercial rebreather to have EN61508 applied.
  • In fact, it is the first diving project to have it applied.
  • Unique publicly spirited attitude of StatoilHydro and its partners in this programme, has created a genuine safety wave which is sweeping through rebreather companies
  • The project has overflowed into the recreational dive industry. At current rates of rebreather take up, this project will save the lives of 22 recreational rebreather divers per year. These usage rates are growing.

Objective was to create a solid platform for commercial diving achieving a much higher level of diver efficiency, operational cost savings and mobility but making a quantum leap upwards in safety at the same time: “have your cake and eat it”.


EN61508 Step 1: SIL Assessment

  • SIL 1: Defect will cause an injury in 10^6 hrs (a million hours)
  • SIL 2: Defect will cause a loss of limbs or sight in 10^7 hrs
  • SIL 3: Defect will kill a few people in 10^8 hrs
  • SIL 4: Defect will kill > 20 people in 10^9 hrs (a billion hours)

The assessment of rebreathers (

  • Mass produced rebreather assessed at SIL 4.
  • Low volume rebreather assessed at SIL 3
  • Communications to diver assessed as SIL 1, treated as SIL 2

SIL 1 (Mira shower) SIL 2 (industrial guillotine) SIL 3 (safety interlock) SIL 4 (Aircraft control)


EN61508 Step 2: Safety Process

  • Covers the entire product life cycle
  • Strong emphasis on specification and verification
  • Training requirements for Project Leader and designers
  • Accident studies, accident investigation capabilities
  • HAZIDs and HAZOPs involving clients, users, designers
  • MTBF and MTBCF, for proof of electronic reliability
  • Higher SIL levels require a mathematical proof of safety (formal specification and formal modelling)
  • Independent audit
  • Openness. Publication of all safety, compliance and verification documents.

Benefiting the entire industry

  • Decision to disclose the most fundamental safety techniques rather than patent them
  • Five most basic safety innovations from this programme already adopted or being adopted by other rebreather manufacturers
  • It has established a central database of rebreather fatal accidents, for the first time
  • It has provided a detailed case study of how to apply all the standards in full, to the letter
  • It has created the commercial diving rebreather on display here. The intent is this will be available widely, providing increased safety and reduced operating costs to the entire commercial dive industry