Evaluation of Models and Accept Criteria for Technical Condition of Ship Systems and Equipment

Abstract

Maintenance is today an increasing part of the shipping industry. The demand for safer operations, lower emissions and low downtime is constantly increasing. As a result of this more complicated and complex system is developed and the focus on maintenance and efficient operations is becoming more and more important. As a result of this, models such as the TCI concept has been invented.

The TCI concept is based on condition monitoring of the combustion process in the cylinder and the involved equipment. The objective is to detect slowly developing deviations in parameters related to efficiency, safety and environmental condition of the propulsion function. This is done through monthly measurements by the crew and sent to the TeCoMan database for processing. There the measurements are normalized for engine load and ambient conditions to be able to compare the results with reference values collected from the sea trial and equipment manufacturer. The measurements is then transformed to TCI’s which can be explored by the crew and administrators in the TeCoMan program. The TCI value reflect the severity of the performance and will decide what actions needs to be taken, and makes it possible for the crew and administrators to plan the maintenance

The problem with the TCI model has been the "noisy" behaviour for the different parameters and the goal for this thesis has been to address this problem. Data from the TOCC project has been used throughout the project, one series of seven ship and one series of four ships. A in- depth study and a sensitivity analysis to study the influence of the correction factors has been done, where the mean effective pressure, cylinder pressure and the scavenging air pressure are the factors that were found to have the biggest influence.

To identify the reason for the noisy behaviour each ship was studied to find the root cause. For the series with seven ships, erroneous measurements for both the parameters itself and the correction factors, are the main factor for the variations in the efficiency TCI’s. This errors results in large deviations for the corrected values and thus low TCI values. For the degradation it is the scavenging air filter pressure drop and fuel pump index which have the lowest TCI’s. For the scavenging air filter the low performance is due to the varying measurements done by the U-tube manometer. For the fuel pump index the corrected values are wrong due to a fuel flow of 0m3/h. For the second series the large variations in both the measured parameters and the parameters used for correction, such as mean effective pressure and cylinder power, are the cause for the low TCI’s for both the efficiency and the degradation.

With defined limits for the parameters based on expert opinions a large portion of the erroneous measurements would be eliminated. Also adjustment of reference and correction values for each ship due to individual differences could enhance the TCI performance. For the second series the routines for the different measurements needs to be improved. Good procedures and trained workers will help to keep the variations at a minimum. For unstable parameters lower weighted sum can be used to decrease the influence to aggregated systems.