Shell Pernis 11.2t Ethylene Oxide Leak

Shell Pernis 11.2t Ethylene Oxide Leak

The Dutch Safety Board has reported (in Dutch) on the leak of 11.2 tonnes of ethylene oxide from a overhead pipe at the 550 hectare Shell Pernis oil refinery on 30 December 2013. The leak was detected by a site worker at what is Europe’s largest refinery, surrounded by 500,000 inhabitants.

Shell Pernis Refinery (Credit: Steven Lek CC BY-SA 4.0)

Shell Pernis Refinery (Credit: Steven Lek CC BY-SA 4.0)

Ethylene oxide is toxic, carcinogenic, ignites easily and may explode.  The DSB say their investigation shows that Shell was not prepared for such a leak of that size.  The adjacent port had to be evacuated due to the level of airborne contamination, and a water curtain used had the side effect of increasing the ground contamination.

The spill occurred because the insulated pipework joints has degraded internally over 18 years.  The DSB say that Shell had assumed a 40 year design life and that the joints would be maintenance free for 20 years.

Following the spill, Shell has taken a series of measures. The joints have been replaced by flanges which can be routinely inspected.  Shell now uses technical means to detect leaks in a timely manner and emergency procedures have been revised.

Shell Pernis Refinery (Credit: Steven Lek CC BY-SA 4.0)

Shell Pernis Refinery (Credit: Steven Lek CC BY-SA 4.0)

Not The Only Leak

Shell had suffered leaks of the same chemical in 2007 and 2009.  During the completion of this report, the DSB launched an investigation into the emission of another 25 tonnes of ethylene oxide at a sister plant at Shell MoerdijkIt is alleged that this leak, following a repair in November 2015, was only discovered 2.5 months later.

We have also previously reported on an earlier explosion there: Shell Moerdijk Explosion: “Failure to Learn”

UPDATE 10 August 2016: It is reported that the UK Health and Safety Executive (HSE) have issued an Improvement Notice to Shell in the UK on its Clipper Southern North Sea complex of five bridge linked platforms, after one of their inspectors warned that:

…“significant changes” to the Clipper installation meant there was risk of loss of containment from corrosion under insulation (CUI).

In one instance, a four inch condensate line had to be shut down after it was discovered the thickness of the wall was just 2.6mm – a significant decrease on its nominal measurement of 11.1mm.

A notice from the HSE also said “certain hydrocarbon containing lines” were three years behind their planned inspection date while certain lines had not been inspected for more than 12 years.

But further:

It was also found Shell had reduced its CUI inspection and repair programme staffing in March from 24 persons to eight people, which reduced the “ability to execute inspection and repairs in a timely manner”.

In the 2008 book Resilience Engineering Perspectives, Volume 1: Remaining Sensitive to the Possibility of Failure, John Wetherall writes:

…one hallmark of a resilient organisation is that it is prepared not only for its own failures those of which it can learn from others – the more resilient it is, the ‘bigger’ are the lessons it has learnt from others.

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