URV Chairs
ENRESA-URV Industrial Safety Chair
Accidents described in the Case Histories
Below we describe some examples of simple accidents that have occurred, taken from “Case Histories”.
Static Electricity
Explosion during a tanker loading operation
Two workers were loading a tanker with vinyl acetate. One of the operators was on the roof of the tanker, the other on the ground. A few seconds after the operation began, the tank exploded. The worker on the roof of the tanker was thrown to the ground suffering a cerebral fracture and multiple burns, from which he died shortly afterwards.
The accident investigation revealed that the explosion was caused by a spark, generated by static electricity, from the metal strip on the tank filling hose. The strip was not earthed and it is likely that using the (non-metallic) hose contributed to the event.
Explosion in a centrifuge
A centrifuge is used to separate a liquid from a solid. A soft mixture with 90% methylcyclohexane and 10% toluene was fed from a chemical reactor to a centrifuge. A worker observed the result when the centrifuge exploded. The lid came off with the explosion and a huge fire occurred. The worker suffered burns on the hands.
The load line from the reactor to one metre of the centrifuge was made of steel coated in teflon. This final section was made of rubber up to a short line of steel, also cased in teflon, which came out of the centrifuge.
The accident investigation revealed that the flammable atmosphere was caused by the entry of air in the centrifuge and that the cased centrifuge caused the ignition owing to an accumulation of static electricity and the resulting discharge.
Chemical Reactivity
Explosion of a bottle of isopropyl ether
A chemist in a laboratory needed ether. He found a half litre glass bottle. He tried to open it but could not; the screw top appeared to be stuck. He held the bottle against his stomach with one hand and unscrewed the top with the other. Just at the moment the top came undone, the bottle exploded, destroying his stomach and blowing off some of his fingers. The victim died after a couple of hours, but was sufficiently conscious to explain the accident in a coherent manner.
It was proven that the explosion was due to the rapid decomposition of the peroxides that had formed in the ether during storage. The most likely hypothesis is that some of the peroxides had crystallised in the thread of the cap, and exploded when the man tried to remove it.
When such ethers age, in particular isopropylic ether, they form peroxide and ether and these react even more, obtaining highly unstable derivatives such as triacetone peroxide.
Decomposition of nitrobenzene sulphonic acid
A reactor with a capacity of one cubic metre underwent a violent explosion that launched it through the roof of the building. It ended up on the roof of an adjoining building. The reactor was designed to contain 250 litres of sulphuric acid and nitrobenzene sulphonic acid, which it was believed would decompose at 200ºC.
The investigation revealed that the mixture had been maintained for 11 hours. A leak in the vapour serpentine tube heated the mixture up to 150ºC. Tests carried out after the accident demonstrated that the highly exothermic decomposition began at 145ºC.
Organic oxidation
Some workers were preparing an organic oxidation reaction. They were applying vapour to an external serpentine tube to heat a mixture of an organic product with sulphuric acid up to 70ºC. The heating process was taking longer than usual. An operator went to look for a thermometer. He disconnected the agitator and the vapour entry point. After approximately one hour the worker was now ready to measure the temperature through an inlet. He started up the agitator and the solution in the interior was suddenly expelled in a violent manner, soaking the workers who died as a result of the accident.
The results of the investigation reveal that the agitator should not have been switched off since the refrigeration was not effective and local hot spots occurred. Furthermore, materials became segregated and stratified, so that when the agitator was switched on the hottest chemical products mixed with each other and reacted violently.
Historical record of accidents
- Accidents described in the “Case Histories"
- Accidents caused by design errors (described by J.A Davenport)
- Historical record of catastrophes