The shift of oil and gas exploration, extraction and processing to offshore deep sea locations has numerous implications for those entrusted with protecting life and assets from fire. For refineries, terminals, pipelines and chemical plants onshore, there are similar concerns, because hydrocarbon fires, no matter where they occur, can reach excessively high temperatures in a matter of minutes.
Structural steel under load loses over 20 percent of its strength at 950 F (500 C), and over 50 percent of its strength by 1,100 F (600 C), depending on the width of the steel piece. A simple hydrocarbon pool fire rages at that temperature within 5 minutes; jet fires experience a rapid rise in less than 1 minute. Among the concerns with any fire event is protecting fire responders and occupants, as well as preventing the escalation of fire, blocked escape routes and outright structural collapse.
The fires most people think of are cellulosic, i.e., their fuel source is wood, carpeting or drywall and the temperature rise is more gradual. When the fuel source is hydrocarbon-based – involving gasoline, crude oil, liquid gases or solvents – certain scenarios can lead to the potential collapse of interior and exterior steel structures.
- Most common is the pool fire, resulting from the ignition of spilled cargo under normal ambient conditions. If there is a coating already protecting the steel, these fires do not erode that coating to any significant degree.
- A jet fire occurs from a leak of highly volatile liquids or gases in a high-force, pressurized situation such as a riser, pipe or vessel. These fires are very erosive of the incumbent coating.
- A cryogenic spill on liquefied natural gas (LNG) vessels and support structures could, in a matter of seconds, lead to cold-induced brittle fracture, simply from the thermal shock of going from ambient temperatures to -260 F (-162 C).
- A blast or explosion can lead to a fire if, as an example, it causes the rupture of an adjacent structure or vessel leading to the release of inventory, producing a pool fire.