Statement :
The Belgian Royal Decree for the navigation at sea of inland vessels allows short trajectories in coastal waters, between two Belgian ports, given that certain safety requirements are met. This is a very useful approach to tackle lacks in the inland waterways network with temporal and economic scales orders of magnitude lower than the ones associated with a renewal of the waterways infrastructure. While the study is focused on Belgian coastal water, the general concept of the probabilistic sea-keeping analysis can be applied to any other area of interest where an extension of the operational range of inland vessels could benefit the total efficiency of waterborne transport.
Abstract :
The Belgian Royal Decree of 2007 [1] allows inland vessels meeting certain requirements to perform a non-international sea journey. In order to allow an inland vessel at sea, the Royal Decree stipulates stability requirements as well as the need to perform a full probabilistic analysis to assess the behaviour of the vessel in waves. The risk analysis is exempted for tankers and closed hatch vessels sailing up to 1.2 m significant wave height. For such vessels, deterministic requirements on the freeboard replace the probabilistic analysis of vertical relative motions.
After ten years of practice, the need to evaluate the performances of the Royal Decree arose, in particular with respect to inland container and bulk cargo vessels, for which the deterministic exemption is not applicable. In the present work, four reference vessels are selected as representative examples of existing container/bulk cargo vessels based on an extensive study on the current European inland fleet. For each of the four reference vessels, the possible range of loading conditions is investigated and three significant conditions are selected. Finally, the Royal decree requirements regarding stability and vertical relative motions are analysed in detail for each vessel and loading condition.
Based on the results of the analysis, a new set of deterministic requirements for the distance between the free water surface and stipulated reference levels is proposed. These rules are applicable to all types of inland vessels and could replace the existing exceptions for tankers and closed hatch vessels. Therefore, all types of inland vessels could obtain a certificate to sail in significant wave heights up to 1.2 m based only on deterministic requirements. This goes hand in hand with the new regulation imposed by Bureau Veritas, which allows all types of inland vessels to obtain a certificate for sailing between 0.6 and 2.0 m significant wave height, using the IN(x) notation. [2].
As for stability, the actual requirements in the Royal Decree mirror the ones prescribed for ocean going vessels by the International Code for Intact Stability. The present analysis points out that such requirements are too strict to be met by standard inland vessels. Therefore, new stability rules are proposed which impose similar values for dynamic stability reserves, but up to the low flooding angles attained by inland vessels. Moreover, the environmental loads considered in the Weather Criterion, designed for heavy beam seas at ocean storm conditions, are replaced by lower figures, more appropriate for the met-ocean conditions expected along the coastal trajectory.
[1] Belgisch Staatsblad (2007) “Koninklijk besluit betreffende binnenschepen die ook voor niet-internationale zeereizen worden gebruikt”. BS, 16.03.2007, N. 2007 – 1187, p. 14699-14711
[2] Bureau Veritas (2014) “Rules for the Classification of Inland Navigation Vessels – November 2014 Edition”.