PSI - Issue 20

Marina Zakharova / Procedia Structural Integrity 20 (2019) 108–112

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Marina Zakharova / Structural Integrity Procedia 00 (2019) 000 – 000

1. Introduction Increase in industrial safety of hazardous objects in the conditions of the Arctic demands comprehensive account of climatic factors, specific to this area, on risk parameters. In the conditions of the Arctic, the defining external factors are the low temperature of atmospheric air and abnormal weather conditions which are characterized by powerful long temperature inversions in combination with calm. These external parameters of the environment have an impact both on the frequency of accidents, and on development of accidents. In the Siberian region of the Arctic, anti-cyclonic circulation develops in the winter. In these areas very low air temperatures, small overcast, an insignificant amount of precipitation and light or moderate breezes are noted. Aver age temperatures of the coldest winter month, January, ranges from −45 to −50 °C. The minimum temperatures in these areas sometimes drop to −55 ….−60 °C. As a result of strong cooling of a surface in these areas, inversions of air temperature are constant. For elements of technical systems situated in the North, the defining external factor is represented by low temperatures of atmospheric air, which impair the basic physical and mechanical properties of structural materials and increase the possibility of their brittle fracture. To studying of a problem of ensuring cold resistance and brittle fracture probability assessment of structural elements are devoted by Ivanov et al. (2010), Matvienko and Bolshakov (2012), Bolshakov (2012), Bol’shakov and Andree v (2014), Matvienko et al. (2015), Bol’shakov and Andreev (2016), Bol’shakov and Zakharova (2016). 2. Risk analysis of accidents in reservoirs at low temperatures By results of the analysis of accidents in the reservoirs which occurred at low temperatures the main reasons for brittle fracture are established. Fault tree of brittle fracture of reservoirs is developed in fig.1. According to the analysis of reservoir fractures at low temperatures, brittle fracture is implemented only at existence and joint manifestation of the following factors: existence of defects, emergence of additional tension and decrease in crack resistance of material. Accidents are accompanied by the discharge of a large amount of oil products, which pose a serious threat to the environment. A specific feature of the Arctic regions is the presence of permafrost. During spills, oil gets deep into to a zone of thawing and continues to spread laterally over this zone, being exposed to very slow transformation. Duration of self-recovery of the soil at the average level of pollution in the conditions of the North is estimated by different researchers from 10 to 15 years.

Brittle fracture of reservoirs

and

emergence of additional tension

existence of defect

decrease in crack resistance

or

or

or

through cracks, fistulas

ageing

steel of poor quality

uneven rainfall bases of reservoirs

external action

low temperatures

influence of ambient temperature

untimely technical diagnostics

Fig.1. Fault tree of brittle fracture of reservoirs at low temperatures