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문제 정의
- The DP vessel is known for its feature to maintain a certain position on the sea or accurately follow a path due to the nature of its works, and there are around 7,000 or more DP vessels around the world. This study aims to implement the FSA for the safe operation of DP vessels.
- This study calculated the expenses incurred to reduce the risk of LOP incidents of DP vessels. In addition, in case of NCAF, expenses incurred for protection of human life, values of vessel and cargo at the time of total loss, crew and repair expenses, etc.
제안 방법
- Next, the Bayesian Network was applied to quantitatively examine the probability of PRS errors. In order to classify 117 PRS-related DP LOP incidents by the occurrence of failure in the MS Excel file, this study created a flow chart, ran the Excel file on the GeNIe, and examined the prior probability of DP LOP incidents as in Fig. 2. The leftmost factors indicate 10 kinds of errors by the PRS, and six factors represent the types of PRS used on the DP vessels.
- In order to confirm the frequency of reduced occurrence of drive off, operation abort and time loss in the DP simulation upon application of each of the RCOs, the DPO was set to make an Offshore Supply Vessel (OSV) approach a semi-submersible drilling rig. The approaches were made, by 25 times each, from places 250m apart from each side of the drilling rig as shown Fig.
- In order to confirm the reduced risk level through the application of RCOs, this study checked the reduced risk level by applying DP simulation to A1, B1, C1 and E1. As D1 and F1 were not installed in the model DP vessel of a simulator, this study were not able to apply D1 and F1.
- Second, the F-N curve based on the analysis of frequency and Bayesian Network demonstrated that parts of drive off and time loss were beyond the reasonably tolerable risk of LOP incidents caused by PRS errors. In order to reduce risks to reasonably tolerable scope, this study proposed the RCO to install more than two types of PRS on every DP vessel. The effect of the proposed RCO was examined in simulation, and it was found that the average risk reduction stood at 17%.
- Next, the Bayesian Network was applied to quantitatively examine the probability of PRS errors. In order to classify 117 PRS-related DP LOP incidents by the occurrence of failure in the MS Excel file, this study created a flow chart, ran the Excel file on the GeNIe, and examined the prior probability of DP LOP incidents as in Fig.
- So far, this study conducted the FSA from Steps 1 to 4, and based on the FSA on the PRS of the DP vessels in Step 5, this study make the following recommendations to mitigate risks of DP LOP incidents caused by PRS.
- The FSA implementation requires the analysis of all incidents that occurred for a certain period of time. This study analyzed prior probability and conditional probability of PRS errors on the drive off, time loss and operation abort of the DP vessels based on the application of the Bayesian Network. This enabled the quantitative analysis on the DP LOP incidents that occurred during a certain period of time, and we would like to propose effective methods to prevent DP LOP incidents in the areas with high frequency.
- This study conducted the FSA on PRS errors, the main cause of DP LOP incidents identified in previous studies, for safe operation of DP vessels, and the results are as follows.
- This study have proposed the RCOs to control risks of LOP incidents caused by PRS errors through experts’ brainstorming as provided in Table 12 based on the standards mentioned in the IMO’s FSA.
이론/모형
- To be granted the experts’ consent through brainstorming and determining priority of the proposed items, this study applied the expert concordance matrix as stated in MSC 83/INF.
성능/효과
- As a result, the probability of LOP incidents caused by PRS errors is shown to be 48% for time loss, 41% for drive off and 14% for operation abort. In addition, in case of PRS, DGPS errors turned out to be the highest at 54%, the causes thereof were shown to be a signal weak or fail at 21% and hardware failure of PRS devices at 19%.
- First, 117 DP LOP incidents caused by PRS errors were analyzed based on the Bayesian Network, and the conditional probability of PRS in drive off was found to be 57.0% for the DGPS, 31.7% for the HPR, and 19.6% for the Microwave system. Moreover, it was verified that the main causes of such errors were signal weak or fail, hardware failure, external influences, etc.
- Fourth, in the process of FSA implementation, it was found that the Bayesian Network could be useful in risk analysis. Further, simulations were found to be useful tools to prove effectiveness of the proposed RCOs.
- As a result, the probability of LOP incidents caused by PRS errors is shown to be 48% for time loss, 41% for drive off and 14% for operation abort. In addition, in case of PRS, DGPS errors turned out to be the highest at 54%, the causes thereof were shown to be a signal weak or fail at 21% and hardware failure of PRS devices at 19%.
- Second, the F-N curve based on the analysis of frequency and Bayesian Network demonstrated that parts of drive off and time loss were beyond the reasonably tolerable risk of LOP incidents caused by PRS errors. In order to reduce risks to reasonably tolerable scope, this study proposed the RCO to install more than two types of PRS on every DP vessel.
- In order to reduce risks to reasonably tolerable scope, this study proposed the RCO to install more than two types of PRS on every DP vessel. The effect of the proposed RCO was examined in simulation, and it was found that the average risk reduction stood at 17%. Moreover, as a result of brainstorming, it was found that training of PRS type specific may reduce the risk of LOP incidents by about 30%.
- Third, after applying the amount of reduced risks to the F-N curve, this study found that drive off and time loss were within the scope of tolerable boundary of ALARP. Moreover, it was confirmed in the cost-benefit assessment of the proposed RCOs that installing more than two types of PRS and providing training of PRS type specific were also reasonable in terms of cost-benefits.
- 1, moved to the Tolerable if ALARP part. Through the above, this study was able to confirm that installation of more than two types of PRS on every DP vessel and training about the relevant equipment would be able to bring resonable amount of reduction in the risk of incidents of drive off, operation abort and time loss on DP.
후속연구
- The cause analysis of the Loss of Positioning (LOP) of DP vessels conducted in precedent studies showed that the major cause of DP LOP incidents for the decade was an error in the Position Reference System (PRS), accounting for 117 cases(Chae, 2015). Based on such findings, this study aims to examine the probable impact of PRS errors on DP LOP incidents by conducting the FSA to 117 DP LOP incidents caused by the PRS, presents propose the risk control options (RCOs) to prevent DP LOP incidents, and proposes the ways to mitigate hazard based on cost-benefit assessment.
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