parameters such as lime saturation (LSF) and coating (CF) factors as shown in Figure 14. LSF is a measure of the lime content of kiln feed. In essence, the higher the LSF, the greater the percentage of un-combined lime which will require additional heat energy to burn. While it is recommended to maintain substantial LSF values, it is crucial to control the amount of free lime due to its ability to continuously trap moisture and cause cracks in cement structures. Looking at Figure 14(a), LSF values within the six weeks preceding K1 brick incident constantly exceeded the target values. The CF shown in Figure 14(b) is a measure of how well K1 refractory bricks in the burning zone are protected by the layer of coating formed by molten clinker. For CF, the target of 26-30 was not maintained. plant’s The success of FTAs is a function of the familiarity of the failure investigation team, which is perhaps the reason why there is a brainstorming element to most FTAs. RBDs on the other hand provide a means of further exposing the interactions between the various causal elements so that system vulnerabilities can be easily identified. For each the resultant fault trees (Figures 10-12), an equivalent RBD (Figures 15-17) was also developed based on the rules defined by Labib and Harris [27]. In addition to the individual RBDs, a global RBD that integrates the individual equivalent RBDs is also shown in Figure 18 so that the interface between the different classes of failure causes can be easily visualised. The integrated RBD depicts a very fragile interaction between the different events, owing to the significant number of associated series structures. The causal factors in the RBD are mostly related to the poor culture of maintenance and operations in the plant, although it can also be argued that a more recent K1 burner pipe design with deflection measurement capabilities will aid the early detection of misalignment. 5. Recommendations from the failure investigation team A significant number of the current investigation team members were also involved in the initial failure investigation using the Apollo method. However, unlike the earlier exercise that purely dwelled on external factors (outward-looking) such as brick design and therefore recommended the usual action of refractory brick replacement, the current investigation based on FTA and RBD provided more insights about inherent lapses in the maintenance, operation and quality practices within the plant. Therefore, Table 2 provides an action plan
parameters such as lime saturation (LSF) and coating (CF) factors as shown in Figure 14. LSF is a measure of the lime content of kiln feed. In essence, the higher the LSF, the greater the percentage of un-combined lime which will require additional heat energy to burn. While it is recommended to maintain substantial LSF values, it is crucial to control the amount of free lime due to its ability to continuously trap moisture and cause cracks in cement structures. Looking at Figure 14(a), LSF values within the six weeks preceding K1 brick incident constantly exceeded the target values. The CF shown in Figure 14(b) is a measure of how well K1 refractory bricks in the burning zone are protected by the layer of coating formed by molten clinker. For CF, the plant’s target of 26-30 was not maintained. The success of FTAs is a function of the familiarity of the failure investigation team, which is perhaps the reason why there is a brainstorming element to most FTAs. RBDs on the other hand provide a means of further exposing the interactions between the various causal elements so that system vulnerabilities can be easily identified. For each the resultant fault trees (Figures 10-12), an equivalent RBD (Figures 15-17) was also developed based on the rules defined by Labib and Harris [27]. In addition to the individual RBDs, a global RBD that integrates the individual equivalent RBDs is also shown in Figure 18 so that the interface between the different classes of failure causes can be easily visualised. The integrated RBD depicts a very fragile interaction between the different events, owing to the significant number of associated series structures. The causal factors in the RBD are mostly related to the poor culture of maintenance and operations in the plant, although it can also be argued that a more recent K1 burner pipe design with deflection measurement capabilities will aid the early detection of misalignment. 5. Recommendations from the failure investigation team A significant number of the current investigation team members were also involved in the initial failure investigation using the Apollo method. However, unlike the earlier exercise that purely dwelled on external factors (outward-looking) such as brick design and therefore recommended the usual action of refractory brick replacement, the current investigation based on FTA and RBD provided more insights about inherent lapses in the maintenance, operation and quality practices within the plant. Therefore, Table 2 provides an action plan
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