Estudio de las poblaciones microbianas

Ship repair can be described as a typical make-to-order operational system. The process of repairs, starting from taking the order up to the delivery of the vessel, is very complicated.

- 46 -

Ship yards, even the ones that are specialized on ship repair and maintenance, often make ad-hoc plans for the repair activities and hence use their resources inefficiently. In managing such complex operations requires the utilization of effective project planning and scheduling in all phases of the repair process including the management of human, material, facility and all reusable resource factors. What is even more challenging but also crucial is the alignment of all different resource factors such that they are used most efficiently in a collective manner. Without having such alignments among the resource factors cause workers or equipment to wait idle until the prerequisite activities are accomplished during the repair process.

Before the computers were used for planning and scheduling activities in shipyards, managers planned and scheduled their operations manually with using some basic charts. After the development and introduction of scheduling methods like Critical Path Method and Program Evaluation and Review Technique, shipyards started to apply such methods in their daily operations and experienced improved utilization of their resources. However, such methods have never been effective enough to guide the management of complex problems. In order to resolve the problems related with resource constraints more advanced techniques like branch and bound algorithm, zero-one programming and genetic algorithms have been introduced and used widely in the industry. But their effectiveness in addressing Resource Constrained Scheduling Problems has also been limited.

Effective management of resources is crucial and it is regarded as one of the most important success factors in almost any project, regardless of the size and complexity of the project. For a shipyard, the profitability and successful delivery of projects are very much dependent on the utilization of the shipyard’s resources.

As it is the case in any typical operation in a shipyard, in repair and maintenance activities there are different stakeholders involved all aimed to achieve one ultimate goal. Some of these stakeholders are;

 The shipyard company

 The ship-owner / operating company  Suppliers – Sub-contractors

 Classification societies

These different groups would come together either to plan and implement some maintenance activities that could prevent the breakdowns before they happen. This is called preventive maintenance and it does not only prevent the breakdowns but also many costs that could realize if such actions are not taken. In another case, the stakeholders might also be involved in projects to repair a ship which already had certain problems. This is

- 47 -

called as corrective maintenance and it is needed when a certain equipment or component of the ship fails and this leads to (or might have the potential to lead to) a downtime in ship’s operation. The cost of this maintenance is much higher than the cost of preventive maintenance.

There is a causal relationship between these two types of maintenance activities. Through preventive maintenance activities, the aim is to eliminate all the incidents which might cause a corrective maintenance. In other words, if there is not a proper and effective preventive maintenance management, then there will be more corrective maintenance activities that will be needed in soon time. In this case, overall repair and maintenance costs will increase and ship operator will lose a significant amount of time in the operational life of the ship.

Whether the maintenance activity is preventive or corrective, the partners that are involved in the process needs to exchange information while each has to do their own tasks in the proper way. However, the process is very complex just as the shipbuilding operations (Chryssolouris et al. 2001);

 One day operation loss has huge economical loss for the ship-owner. All the data about the ship repair / maintenance needs to be exchange quite quickly. At the same time, this should be done in a consistent way.

 It is not easy to anticipate the required maintenance activities at the very beginning of the process. Even identifying the required work takes important amount of time. The breakdown may be caused by or may have caused problems that are related with other parts or components of the ship.

 There are many parts that are involved in this process. Some will be repaired and some will be renewed. These parts are not supplied by one single company. There are different suppliers that will be involved in the process and all needs to follow the tight schedule and the shipyard is responsible for their follow-up.

Process starts when the shipyard receives a request from the ship-owner for the maintenance or repair activity. After the project is initiated, based on previous experiences and specific needs for the requested maintenance activity, shipyard starts planning the activities to carry out. Then, shipyard communicates with several internal and external suppliers and places orders for some parts and components. After the ship is in the yard for inspection, they gain more information about the required activities and shipyard orders more components from their suppliers and might request work from some of their sub- contractors. Throughout this process, a lot of communication takes place and the accuracy

- 48 -

and speed of the communication is extremely binding for the successful delivery of the project.