Damage to petrochemical facilities during earthquakes: Fid-Bau Portal

Damage to petrochemical facilities during earthquakes

Ozbey, M. Cem / Sari, Ali

Large earthquakes are rare events in even seismically active regions, just like accidental explosions or strong hurricanes. Although the effects of a large earthquake and a strong hurricane are widespread in a region, earthquakes differ from hurricanes as they cannot be predicted before they happen. Accidental explosions are similar to earthquakes in the sense that they cannot be predicted ahead of occurrence. However, earthquakes have some additional consequences that may contribute to the extent of the damage and loss when compared to accidental explosions. Considering the fact that probability of having a large magnitude earthquake is higher than having an accidental explosion at a petrochemical facility in Western U.S., being prepared for a large magnitude event is more important than being prepared for an accidental explosion. Just because a large earthquake did not struck a populated region in Western U.S. in the last hundred years, does not mean that seismic hazard is not present for the region. Some of the additional consequences of large earthquakes when compared to accidental explosions are: Loss of electrical power, damage to water supply pipelines, limited outside help due to overall demand for manpower and extensive loss of life and injuries in the area, blocked access roads, multiple affected sites within a facility, lack of communications, fleeing personnel in search for their families, hazard from adjacent facilities, large aftershocks. As Tupras refinery was designed according to U.S. codes and built by a U.S. company, also considering the similarities between the North Anatolian and San Andreas Fault systems; the damage experience in Tupras can take place in many petrochemical facilities in Western U.S. It should be also noted that the financial looses will be higher for a U.S. facility, considering the relatively-high cost of recovery and possible law suits due to environmental pollution. Also, as Tupras was the most important industrial facility in the region and other chemical facilities did experience relatively low damage, all the local and outside fire fighting efforts were concentrated in Tupras. This may not hold true for a petrochemical facility in Western U.S., where limited fire fighting capabilities can exist for a relatively long period of time. The biggest portion of the fire in Tupras was started by the ignition of Naphtha in some of the floating roof tanks. Sloshing caused by seismic waves ignited the oil inside Naphtha floating roof tanks and caused fires that lasted for days during numerous earthquakes, the earliest being the 1964 Niigata earthquake and the latest being the 2003 Tokachi-Oki earthquake. This shows that, unfortunately, no lessons were learnt from the previous earthquakes in a 40-year period. During sloshing, the floating roof is shaken vigorously by the earthquake together with the uneven settlement of the tank caused by the ground liquefaction, which resulted in ignition of the oil by sparks generated by the collision between the floating roof and the side wall. The sparks were generated by the metal touch sealing between the floating roof and the side wall. To prevent ignition during sloshing, soft touch sealing composed of synthetic rubbers or urethane foams should be used instead of the metal touch sealing. In addition, basic foundation of tanks should be sufficiently improved especially in the areas of ground liquefaction. The improved basic foundation suffers little damage from the uneven settlement.