Decreasing Demurrage Time by Increasing Port Service Level and Utilities Considering Crane Formation Using Discrete Simulation

Maritime logistics has a great influence on large-scale economic development. Maritime logistics has the largest logistics flow in Indonesia. Economic development can be seen by how much logistics flow in an area. The distribution of logistics using sea transportation must be controlled effectively and efficiently so that the flow of material does not stop or be disrupted. Teluk Lamong Terminal is the only green smart terminal in Surabaya, so there are many requests for ships to lean on the pier. The method of this research is to conduct a survey and collect information about the main activities of loading and unloading ships docking at the pier, the number of cranes used, the current crane formation (before improvement) and problems in the operation of containers. After that, create a simulation model that will be developed using Simulation Software that has inputted entities, activities, and model resources according to their actual activities. Scenario results improvements 1 to 4, the selection of crane formations in serving container ship loading and unloading is the most effective in scenario 3, namely by setting 3 cranes to serve 1 berthing ship and 2 cranes to serve 1 berthing ship. In scenario 3 with the simulation results obtained that the ship’s effective time at the dock was 9.19 hours and the demurrage time for container loading and unloading was 13.79 hours. Furthermore, crane utilization value is in scenario 3 with the results obtained from the simulation of 18.21%.


Introduction
Maritime logistics has the largest logistics flow in Indonesia.Economic development can be seen by how much logistics flow in an area.Surabaya is the capital city of East Java which has a dense logistics flow.The distribution of logistics using sea transportation must be controlled effectively and efficiently so that the flow of material does not stop or be disrupted.However, several ports in the city of Surabaya have not been fully managed properly.Teluk Lamong Terminal is the only green smart terminal in Surabaya, so there are many requests for ships to lean on the pier.According to Tama, M.I., et al (2020), at the operational level, uncertainty is very high.For example, the arrival of ships, the arrivals of trucks, the volume of boxes or containers to be transported.According to data from the Central Statistics Agency, loading and unloading activities increase from year to year at the port of Surabaya (2014)(2015)(2016)(2017)(2018).Operational data can be seen in table 1.
1 mahyaindra@untag-sby.ac.idTherefore, it is necessary to increase the service level at the port.If this activity is not reviewed, there will be a lot of queues of ships willing to carry out the loading and unloading process and result in high demurrage times.Through research to overcome these problems, simulations were made from the events of the queue of ships docking to loading and unloading.In addition, it is necessary to arrange the arrangement of the crane which is the main tool or facility to support loading and unloading activities.According to Arkat, J., et al (2016), the adventages of using dock facilities are reduced warehousing costs, maintenance costs, labor costs, and shorter delivery times.Besides that, warehousing costs can be reduced if the movement of goods faster than usual and affect the inventory volumes to be minimized (Konur, D. and Golias, M.M., 2017).
Several studies consider routing decisions for these vessels in minimizing costs and routes.But not to the point of increasing the service level and utility of the tools used (Chopra, H.B. and Patel, P.G., 2015).The research was conducted at the only Green Smart Terminal in Surabaya, East Java, Indonesia.This container terminal is a new port that was built with the concept of an eco-green port and also uses environmentally friendly equipment (using electricity) to run all its operations.In addition, this terminal has increased loading and unloading queues, so there must be some equipment that must be adjusted.Equipment adjustments can be in the form of adjusting the arrangement of the crane formation on the dock.This is an important decision to improve and icrease productivity on port.Distribution and transportation have the function of delivering products from the location where the product is produced to the place where the product is used to create high service (Pujawan and Mahendrawati, 2017).

Green Smart Terminal
Teluk Lamong Terminal is a multipurpose terminal or international logistics owned by PT Pelabuhan Indonesia III (Persero) located in the waters of the Madura Strait at Tambak Osowilangon, Surabaya.This terminal is designed to exceed the density limit for logistics traffic at the Surabaya Container Terminal (TPS), part of the Tanjung Perak Port which exceeds the maximum capacity.Teluk Lamong Terminal has become a strategic port on an international scale.In 2021, the number of visits has increased from 2020 in the same semester, which was 20.97%.Teluk Lamong Terminal is committed to realizing an environmentally friendly terminal by effectively managing environmental impacts through efforts to prevent pollution, conserve energy and contribute to environmental conservation.Teluk Lamong terminal is integrated through an innovative application system in an effort to support the smooth and efficient loading and unloading process.

Smart Port.
Teluk Lamong Terminal which is part of the Indonesian Port (Pelindo) is currently starting to implement internet of things (IoT) based technology for the port world.This is done as part of the effort to transform port automation to smart ports and to meet the need for technology optimization in all aspects of operational activities.Meanwhile Information Communication Technology Senior Manager of TTL, Hadi M Lukmantyo said that TTL already has a master plan to develop their information technology, and this year, TTL has developed technology through Enhancement Terminal Operation System (TOS) which manages the entire port loading and unloading system.In the development process, one of the technologies integrated with TOS is IoT and global positioning system (GPS).The application of both aims to speed up the job assignment process to the truck fleet by identifying the location and status of truck loads in real time.Not only that, Teluk Lamong Terminal is also installing a Radio Frequency Identification (RFID) reader system in each block.The purpose of the RFID installation is to accelerate the operation of the on-lift off truck fleet at the stacking yard.

Jetty.
Jetty structures are generally located in deep sea.To achieve this depth and to have an economic structure, it is preferred to have pile supported structure.Structure becomes flexible with significant number of lateral loads, so care should be taken by designer to select type pile and accommodate pile arrangement in such a way that structure become safe to utilize the berth (Chopra and Patel, 2015).

Crane.
Container lifting equipment from this ship is the main support for port work.He described the crane made by Konecranes, Finland, capable of lifting 35 containers per hour per crane.The difference with the old type, this tool also relies on an electric-powered drive, while the previous series uses diesel.This supports that this port has implemented a green port solution.Containers are standard units that have been designed for simplicity and functionality which add value to storage (Rodrigue and Paul, 2013).

Methodology
The method of this research is to conduct a survey and collect information about the main activities of loading and unloading ships docking at the pier, the number of cranes used, the current crane formation (before improvement) and problems in the operation of containers.After that, create a discrete simulation model, this model operation of a system is represented as a chronological sequence of events (tama et al, 2020).Every event happens instantly in time and marks a change in status in the system.Discrete event simulation is an experimental approach that is often used; allows a high level of detail to be modelled because assumptions about buffer space, processing time distribution, or priority delivery can be modelled that will be developed using Simulation Software that has inputted entities, activities, and model resources according to their actual activities.Discrete event simulation, the system is modeled through a series of queues and activities (Choi and Donghun, 2013).

Conceptual Model
Making this conceptual model starts from the first ship arriving then seeing the status of the ship's queue whether there is a queue or not, if there is no ship it can go to the dock and can carry out the process of loading and unloading containers.In making the conceptual model there are several loading and unloading activities described below:

Simulation Model
After making the system conceptual model then create a simulation model using discrete simulation software that can describe a real system condition.Discrete event simulation has been widely used in logistics and supply chain management (Tako and Robinson, 2012).The data that has been obtained is then processed and entered the arena software to obtain a discrete simulation model.Some of the data needed includes the allocation of the number and formation of cranes in serving container loading and unloading, ship arrival schedules, the number of containers unloaded and loaded, the length of time for loading and unloading operations per ship and other data.According to Yuan, Z., et al (2010), creating a discrete event simulation model using software simulation can analyze several material problems in the harbor's terminal.According to Dewa, M. and Chidzuu, L. (2013), discrete event simulation is an experimental approach that is often used; allows a high level of detail to be modelled because assumptions about buffer space, processing time, or priority dispatch can be modelled.

Model Verification and Validation
The model will be tested at the level of verification, this aims to test the justification and reliability of the model according to observations from the relevant resources.Particularly importnant errors include flow control or entity creation, failure to release resources, arithmetic, and statistical errors (Rosetti, 2015).Furthermore, the model was validated by using the two-sample variance hypothesis test in the Ttest with a significance level of 95%.If the model is not verified or validated, then the model will be reformulated.The hypothesis is shown below and Vallidation results can be seen in table 2.
0 : The model simulation data variance is equal to the real data variance. 1 : The model simulation data variance is not equal to the real data variance.

Present Condition
The model will be developed (improvement) through the simulation that has been made, there are 4 alternative scenarios.The results of these alternatives will be compared to see which scenarios are feasible to use/apply.The response variables used for comparison are service level and crane utility.
Response variables are shown in Table 3 as below and present condition as shown in Figure 2.

Scenario Creation
Ships anchored at the dock will be regulated by the number of equipment to be used in container loading and unloading activities.The current situation is that the total length of the domestic dock is 450 m, the number of crane equipment at the domestic dock is 5 units and the total available container trucks are 50 units.Scenarios can be shown in Table 4 as below and Figure 3.

Effective Time
Effective time is the time used to carry out loading and unloading activities while the ship is in berth.The effective time calculation is from the first time the container is unloaded using a crane until the last container is loaded onto the ship.The results of the effective time of each scenario in carrying out container loading and unloading activities are shown in Figure 4. .

Demurrage Time
Demurrage time is the length of time a container ship docks at the pier, which is calculated from the start of the ship's berth at the pier until the ship leaves the pier.The faster the berthing time, the dock utility increases and the more ships can berth.When the ship docks while at the pier, the results of the scenario are shown in Figure 5.

Crane Utilities
Crane utility is an indicator of equipment utilization in handling container loading and unloading at the wharf.The more utilization of the equipment, the higher the utility of the tool.For the utility crane simulation results based on the scenarios that have been made, the results are as shown in Figure 6.

Conclusion
Scenario results improvements 1 to 4, the selection of crane formations in serving container ship loading and unloading is the most effective in scenario 3, namely by setting 3 cranes to serve 1 berthing ship and 2 cranes to serve 1 berthing ship at the wharf.

Table 1 .
Operational Data Loading and Unloading

Table 2 .
Validation Results

Table 3 .
Response Variables