IEC 61508 Safety Case: Rebreather FMECAs

The FMECA files supporting the Open Safety family of rebreathers: all variants of the Incursion Multi-Mode Rebreather, Umbilical Supplied Rebreather, and its two sports rebreathers.

The FMECAs below comprising nine volumes in total: V1 to V9, with V9 being the compliance check.

FMECA V6 in particular is a key industry resource created by the project, that is applicable to all rebreather developments by all manufacturers. FMECA 4, 6 and 7 form an essential checklist before releasing any rebreather into manned trials or into the market.

Fault Study Turbulent CO2 Bypass in Rebreather One-Way Valves(1.6MB)
Updated 14th Mar 2011 with extra material. An important fault mode that affects pliable valves, causing higher inhaled CO2 levels for the diver, and distortion of scrubber endurance test data if the fault is present or stimulated by the test. The report includes evidence that the fault is not present in the Open Safety ALVBOV.
Fault Study Effect of Flooding on Breathing Resistance in Granular Scrubbers (180KB)
Republished 2006 report, Effect of water ingress on granular scrubbers. As little as 50g of water causes considerable increases in work of breathing.
FMECA Volume 1: Top Level (308KB)
Last updated 29th May 2009, covering the Open Safety (OSEL) Umbilical, Incursion and OR_Apocalypse rebreather models.
FMECA Volume 2: MTBF and MTBCF of Electronics (52k)
Last updated 29th May 2009.
FMECA Volume 2a: Supporting Excel File of Calculation (248k)
FMECA Volume 3: Electronics (201KB)
FMECA Volume 4: Mechanical Components (4.5MB)
The FMECA of the mechanical component of Open Safety's family of rebreathers. Last updated 21st Au August 2018.
FMECA Vol 4 Appendix A: CO2 Sensor Window Analysis (1.6MB)
FMECA Volume 5: Software and Firmware (568KB)
FMECA covering firmware and software in the Open Revolution rebreathers and rebreather monitors. This covers both primary FMECA and also correct by construction features to avoid failures from design or programming errors.
FMECA Volume 6: Top Down Rebreather Faults (1.6MB)
The top down failure modes, including all failures that could create a safety issue during a dive. This document covers all types of rebreathers, and faults on any rebreather type. Last updated 10th September 2019.
FMECA Volume 7: Rebreather Fault Tree Analysis (22.1MB)
The top down failure modes for a rebreather in the form of a Fault Tree Analysis. Last updated 10th July 2009
FMECA Volume 8: Rebreather Communications (Umbilical Divers Only) (22.1MB)
FMECA for the umbilical diver's rebreather communications, telemetry and thermal balance control system. Last updated 10th July 2009