If there is one industry in which the threat of explosions is evident, it is the oil and gas industry, not only for the fact that it is a business dealing exclusively with highly volatile materials, but that it can be the focus of all manner of terrorist threat. Many buildings in the industry are vulnerable to attack and accessible by water making them relatively easy targets.
This article deals with a very simple matter within the realms of safety – the containment of glass fragments in the event of an explosion. Also considered is the treatment of existing installed glazing as the specification for glazing in new-build situations will be made with cognisance of regulations and the duty to provide as much safety for people as possible.
When it comes to existing glazing, the opposite is most likely the case because it is very rare to find anyone in an organisation with knowledge of what kind of glass is installed. In more than 30 years in the business, one leading installer of fragment retention window film has yet to come across an organisation that has a record of installed glass. The first advice to anyone with responsibility for the fabric of a building or the safety of others is to have the glass recognised and recorded. There is good reason for this, because in the event of an explosion, Home Office figures predict that up to 90% of injuries and fatalities will be caused by fragments of flying glass. Ordinary annealed glass will shatter into sharp irregular shards of glass, whilst toughened glass, like car side-windows, will break into small blunt pieces.
Oil companies have been aware of the dangers of glass in the event of an explosion for some time and at least one, Mobil Oil, has a global policy to apply window film to its buildings. BP has been vigilant in having installed film tested even within the product’s guaranteed life expectancy.
The Nature of Explosions
The nature of explosions and the reaction of glass also needs to be taken into consideration when making safety preparations. When an explosion occurs, glass in the direct line of the explosion will be subject to an air blast loading and, depending on the distance, is likely to be forced into the building at high velocity. Indeed, glass fragments from shattered windows can travel at 30 metres per second. However, the force generated by an explosion will not just affect the side of buildings facing the blast, because the reverberation of energy around buildings will often result in glass failure away from the direct line. In the case of the NatWest Tower attack in 1993, half of all panes of glass on the side away from the explosion failed. Those involved in glass safety are also aware of the fact that, following the first positive energy wave, a second negative phase ensues whereby the vacuum created by the explosion can suck stressed glass back out where it can potentially fall on people below and outside the building.
The energy waves generated by industrial explosions are often of a lower pressure but longer duration than those generated by explosives and gas explosions, for instance, can be up to three times longer in duration than a detonated terrorist bomb. This extended duration could ultimately result in glass failure over a wider area. Conversely, common building materials like brick and concrete are more likely to withstand the lower pressure, longer duration type of explosion, which again, for those in the oil and gas businesses, focuses safety on glazing.
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Health & Safety
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