Failure of an ortho-cresol storage tank 16 January, 2003 Rotterdam The Netherlands

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1 Failure of an ortho-cresol storage tank 16 January, 2003 Rotterdam The Netherlands Accidental contamination Chimical products farm Ortho-cresol Soil contamination Heating coil Corrosion Weld THE INSTALLATIONS IN QUESTION The site involved is a liquid chemicals storage. Two jetties enable loading and discharging operations between ships and the terminal. The storage tank was built in 1968 according to the standards of a big petroleum group. It is isolated and internally and externally coated. It is heated with a 2 diameter steam-coil which is 119m-long. THE ACCIDENT, ITS BEHAVIOUR, ITS EFFECTS AND CONSEQUENCES The accident On January16 th, a ship is discharging ortho-cresol into tank 208. At am, the tank fails and t of ortho-cresol flow out of it on about 3 ha. As a consequence, a vapour cloud rises toward the Vlaardingen urban area located in the vicinity. This substance is corrosive, toxic and causes offensive smells at low concentrations. The consequences There is no one injured. The authorities take charge of the terminal. Neighbouring companies have to stop their activities. Furthermore, in the city of Vlaardingen, the sirens are operated, public transport is stopped and the authorities ask people to shelter in place that is to keep windows and doors closed. The River Nieuwe Maas traffic is interrupted and rail-traffic in Rotterdam - Hoek van Holland is stopped as well. Sheet updated: October 2006 Page 1

2 European scale of industrial accidents By applying the rating rules of the 18 parameters of the scale made official in February 1994 by the Committee of Competent Authorities of the Member States which oversees the application of the SEVESO directive, the accident can be characterised by the following 4 indices, based on the information available. The parameters that comprise these indices and the corresponding rating method are available at the following address: The level 5 of the index concerning the quantity of dangerous materials released (in the meaning of the SEVESO Directive) expresses the 1,700 t of ortho-cresol (dangerous material listed as toxic in the SEVESO Directive) released during the tank destruction (parameter Q1). The level 2 given to the human and social consequences is due to the confinement and the interruption of the public transport (parameters H7 and H8). The level 1 given to the environmental consequences qualifies the 17,000 t of soil that have been contaminated because of the accident. As the economic consequences of the accident are unknown, this level could not be evaluated. ORIGIN, CAUSES AND CIRCUMSTANCES OF THE ACCIDENT Facts No one was near the tank at the moment of the accident. No witnesses of actual tank-failure testimony was available but factual elements were recovered: The outer shell of the tank vibrated; A cloud (described as a steam cloud) was seen around the top of the tank; A large wave (launched by the dike) was seen. It was also noticed that the liquid streamed at a high velocity through an intersecting street towards pump room 1; Hose in pump-room 1 moved fiercely; Sudden increase in steam consumption was noticed. Scenario According to these facts around the incident, it had been possible to set up the following scenario: First, there was a failure of the steam coil in the tank due to: o o Different material thickness over 10 cm-length (remind: total length is 119 m); Corrosion of the steam coil but visually noticeable; Sheet updated: October 2006 Page 2

3 o Inspections recently carried out: in 2001, a pressure test and ultrasonic measurements had been done. Steam pressure rose to 7 bar; steam expanded in the tank, involving turbulences inside it and developing pressure waves. At this time, the tank was 96%-full pression. Due to weakest spot in the hoop, the tank failed because of a bad quality of one of the welds. In fact, the tank was able to withstand the extra pressure caused by expansion of vapour but not the pressure waves. The tank fails in a few seconds and the product flows through the bund. Sheet updated: October 2006 Page 3

4 The tank turns on its side and the roof ripped off and moved onto the bound. Ortho cresol spread over 3 ha. Conclusions of the investigation Photos DR Direct operational activities are excluded as cause. It is clear that the accident is due to the failure of the steam-coil. Indeed, 10 cm piece of coil is from thinner material and is internally corroded. Tank could take the overpressure caused by the expansion of steam but it collapsed due to dynamic pressure. Furthermore a weak weld was found in the third ring of the hoop. Sheet updated: October 2006 Page 4

5 ACTIONS TAKEN The first priority was to clean-up the site, reduce the stench in the surroundings and also to communicate with population. Thus, the following operations were carried out : Empty surrounding tanks and clean up outside bund : the liquid is stored in iso-containers. Engines, such as power shovel, have been necessary to remove the solidified product ; Photo DR Create access to remains and strip remains in order to enable the inspection of these parts of the tank by a technical investigation service. A selection of evidences had to be carried out ; Removal of remains of tank. Moreover, other 6 storages were dismantled. Decontaminated area The total amount of contaminated soil is tons. Photo DR The picture above gives an idea of the site 4 months after the accident. Sheet updated: October 2006 Page 5

6 LESSONS LEARNT Preventive measures Most of them are listed here under: Measures on the steam-heating: Improvement of the inspection methods for steam-coils, Consider the use of other heating medium, Reduction of steam pressure. Investigation by environmental control agency at other locations. Reconsideration of regulations used. Sheet updated: October 2006 Page 6