QMI Atmospheric Sensor (Q10)

The earliest recorded oil mist fires and crankcase explosions dates back to the genesis of diesel engine development, when Rudolf Diesel himself mentioned the problem in his early writings.

However, it was in 1947, following the MV Reina Del Pacifico disaster in which 28 people died, that the dangers of oil mist gained greater attention, though it wasn’t until the early 1960s that the first crankcase oil mist detector was introduced.

The need to monitor the accumulation of oil mist in an engine’s crankcase and machinery spaces was further recognized when classification reports estimated that between 1990 and 2001 some 700 engines were written off as a consequence of oil mist-based crankcase fires or explosions. P&I Clubs went further claiming that up to 65% of all ship fires were the result of pressurized fuel and lubricating/hydraulic oil droplets collecting in the atmosphere of machinery spaces.

QMI Atmospheric Sensor (Q10)

  • The QMI Atmospheric Sensor detects accumulation of oil mist in machinery spaces.
  • Alarms are set at 0.05mg/l to provide adequate warning of a potential fire/explosion hazard. Atmospheric oil mist leaks can ignite immediately.
  • Sensors can be placed in air flow channels or near to ventilation systems and known points of failure.
  • Smoke generators can be provided to assess direction of air flows and turbulence.

This fine, highly flammable mist of between 1 and 10µm is produced at surface temperatures of between 200°C and 600°C, while droplets greater than 50µm are typically produced from pinhole leaks in a pressure line.

In an open machinery space, oil mist or spray of any droplet size must be treated as a potential fire risk and appropriate detection systems should be in place to safeguard ships’ crew and equipment before it becomes a MAIB incident.

The principle used in the early oil mist detection systems – obscuration light absorption – is still used by most manufacturers of oil mist detection systems to this day. The technology involves the extraction of the oil mist from selected points within the crankcase which is then transferred in sequence via discrete pipes to a central detector, usually mounted on the engine, with a facility for remote reading at a centralised panel.

However, these systems have a very slow response time which, in some cases, raises alarm after engine seizure or explosion has actually taken place.

When the lenses become obscured a false alarm can occur.

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