Collision consequence estimation model for chemical tankers

Abstract

Chemical tanker traffic constitutes a hazard for the environment; large chemical spills caused by, for example, shiptanker collisions can have catastrophic effects in similar manner to oil spills. For this reason, it is important to have a generalized spill model for chemical tankers, so that the spill size for a given geographical area can be assessed. The spill volume can be used as an indicator of risk in the given area. Furthermore, such a model can be used to analyze the possible effects of potential risk-mitigating measures such as requiring wider double hulls for chemical tankers. In this article, a spill model is proposed, which for a given collision scenario can model the penetration, spill probability, and size caused by a ship striking a chemical tanker. This is done using finite element method, MATLAB, and statistical metamodels with ship particulars extracted mainly from automatic identification system data from the Gulf of Finland.

Uncertainty in maritime risk analysis: Extended case study on chemical tanker collisions

“…For all struck tankers, t = 1, 2, …, T , in collision candidate situations in the ij th square; N sim is the total number of simulation runs, each representing 1 year of traffic in the GoF; P ct is the relevant causation factor; DW T t is the DWT of the t th struck tanker; N total is the total number of tanks per tanker (= 20) and N t tanks breached is the number of tanks breached in tanker t , which is calculated based on the spill model provided by Sormunen et al 28…”

“…Besides providing an uncertainty analysis and discussion, the study also offers two suggestions for improvement based on results previously presented by Sormunen: 26 first, using a more refined spill model, as presented by Sormunen et al; 28 and second, adapting GoF-specific causation factors based on a Bayesian network model presented by Hänninen and Kujala 29 for a ship traffic simulation conducted by Goerlandt and Kujala. 30 Furthermore, this article presents and applies an empirical distribution for the relationship between a ship’s initial speed and its collision speed.…”

“…The causation factors have been extracted specifically for the purposes of this study by adapting Hänninen and Kujala’s 29 method. The finite element (FE)-based model is described in detail in Sormunen et al 28 (see also Ehlers 31 ). By combining these different factors, it is possible to obtain the expected collision frequency, spill size and probability for any given area and time span in the GoF.…”

“…Once the collision frequency is known, this information can be combined with a collision consequence model to obtain the risk, which is expressed in terms of spill sizes in cubic metres. The discrete spill size estimation model used here is presented in more detail by Sormunen et al 28 This model needs the following input variables:…”

“…The collision consequence model used here is the one presented by Sormunen et al, 28 which analyses the effect of different bulb sizes and double hull widths on collision damage. The model is based on finite element method (FEM) results regarding the relationship between the collision energy, the striking ship bulb size, the double hull width of the truck tanker and the resulting perpendicular penetration depth into the side structure of the tanker.…”