Grijper activiteiten in een bulk import terminal

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Delft University of Technology

FACULTY MECHANICAL, MARITIME AND MATERIALS ENGINEERING

Department Marine and Transport Technology Mekelweg 2 2628 CD Delft the Netherlands Phone +31 (0)15-2782889 Fax +31 (0)15-2781397 www.mtt.tudelft.nl

This report consists of 67 pages and 5 appendices. It may only be reproduced literally and as a whole. For commercial purposes only with written authorization of Delft University of Technology. Requests for consult are only taken into consideration under the condition that the applicant denies all legal rights on liabilities concerning the contents of the advice.

Specialization: Transport Engineering and Logistics

Report number: 2013.TEL.7780

Title:

Grab handling activities in a bulk

import terminal

Author:

B.B. de Keyzer

Title (in Dutch) Grijper activiteiten in een bulk import terminal

Assignment: research - design

Confidential: no

Initiator (university): prof.dr.ir. G. Lodewijks Initiator (company): ir. D. Mooijman (EMO) Supervisor: ir. T. van Vianen

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Delft University of Technology

FACULTY OF MECHANICAL, MARITIME AND MATERIALS ENGINEERING

Department of Marine and Transport Technology Mekelweg 2 2628 CD Delft the Netherlands Phone +31 (0)15-2782889 Fax +31 (0)15-2781397 www.mtt.tudelft.nl

Student: B.B. de Keyzer Assignment type: Research - Design

Supervisor (TUD): Ir. T. van Vianen Report number: 2013.TEL.7780 Supervisor (Company): Ir. D. Mooijman (EMO)

Specialization: TEL Confidential: no

Creditpoints (EC): 15

Subject: Unloading Vessels – spare grab activities

In import dry bulk terminals, sea-going vessels are mostly unloaded by grab unloaders, see for an example figure 1. Grab unloaders move in parallel direction of the quay to the next vessel to unload. Each grab unloader is equipped with several grabs, because the grab type is material type related and grab unloaders have spare grabs. Nowadays, if a crane moves to another vessel, it will bring its’ spare grab with him and put it on the quay in the direct area, to prevent that the grab breaks down and the crane is not able to use immediately the spare grab.

The idea of this assignment is to investigate if the spare grab actions effective unloading time can be saved.

 Investigate literature if methods are published about spare grab actions

 Investigate and describe the spare grabs actions (by visiting and analyzing practical data of the EMO terminal in Rotterdam).

 Generate alternative methods and evaluate the alternatives

It is expected that you conclude with a recommendation for further research opportunities based on the results of this study.

The report should comply with the guidelines of the section. Details can be found on the website. The professor,

Prof. dr. ir. G. Lodewijks

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Grab handling activities in a bulk import terminal

Bj¨orn de Keyzer

Transport Engineering and Logistics,

TU Delft

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Abstract

Materials such as coal or iron ore are transported over the world in bulk carriers. These bulk carriers are unloaded in so called bulk import terminals. A common practice at these terminals is to unload the vessels with grab unloaders. The capacity of these grab unloaders determines the unloading time of the bulk carriers. The grabs on the unloaders are subject to wear, from the abrasive properties of the bulk material, but also from the shocks in the wires during hoisting. Due to this wear, a grab can break during unloading, resulting in delays for the bulk carrier. To obtain practical data on grab handling, the situation at the Europees Massagoed en Overslagbedrijf (EMO) is analysed. EMO has data from four unloaders on four berths, but it is possible to split the terminal in two sections with two unloaders on two berths. A calculation sheet is developed for two unloaders on two berths to calculate the delays per subfunction during unloading and the total delay per vessel. In order to find a better storage solution for the grabs and spare grabs and reduce the delays during unloading, five concepts for grab handling are proposed:

• Randomly store grabs on the quay, without taking spare grabs to the vessel • Grab storage on the back supports of the unloader

• Shielded grab storage between two berths

• Shielded grab storage at the midships of every berth • Central grab storage with a grab mover

The grab handling times for these concepts are evaluated using the same calculation sheet as the present situation at EMO. In order to choose the best concept, not only delays but other criteria such as the number of grabs, storage capacity between the supports of the unloader, safe working regulations and cost are weighted as well in a multi criteria analysis. In 2013, the situation at EMO has changed to five unloaders. Now it can occur that three unloaders work on one vessel. Therefore the calculation sheet for the best two concepts is adapted for the third unloader on one vessel. The same multi criteria analysis is performed for the new situation. In both the cases of two and three unloaders on one vessel, the delays due to grab handling during unloading can be reduced. The shielded grab storage at the midships of every berth proves to be the best concept.

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Introduction

In this report, an analysis is performed on grab handling in a bulk import terminal. The delays due to grab breakdowns are influenced by the way the grabs are stored in the terminal, as will be shown in the next chapters. In this chapter, an introduction to bulk materials will be given in Section 1.1, followed by the transport process of large scale bulk transport in Section 1.2. Then the problem definition will be given in Section 1.3, with the goal of this research. Finally, at the end of this chapter, in Section 1.4 a graphical overview of the contents of this report will be given.

1.1 Bulk material

Bulk materials are transported in large quantities as unpacked cargo. Bulk materials exist in solid or fluid form, but in this research only bulk solid materials will be considered. Examples of bulk solid materials can be sand, coal and iron ore, but even consumption goods such as grain or salt are transported in bulk. First, the most important properties of bulk solid materials will be discussed in Section 1.1.1, secondly markets for different bulk materials will be discussed in Section 1.1.2.

1.1.1 Properties

The definition of bulk solid materials is as follows: A bulk solid material is any assembly of dis-crete solid components or particles of whatever size range, substantially in contact or near contact with immediate neighbors. Important properties of bulk solid materials are the bulk density and the angle of repose, which is defined as the critical angle beyond which the material flows freely, see Figure 1.1. These two properties are dependent on other properties of the bulk solid material, such as the particle size, particle shape and moisture of the material. The angle of repose, density and particle size of some common bulk solid materials are given in Table 1.1. For some bulk materials, degradation can be a problem. Degradation is the decline in quality or value of the bulk material. It can occur in several ways, for example if the material breaks during transport or if the moisture content becomes too high.

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Figure 1.1: Angle of repose α[15]

Material Angle of repose [◦] Bulk Density [kg/m3_] _{Particle size [mm]}

Sand 20 - 35 1600 - 1800 0.5 - 2 Gravel 30 - 50 1500 - 2000 3 - 50 Coal 35 - 38 800 - 1400 >0 - 100 Iron ore 35 - 40 1500 - 7000 >0 - 150 Grain 25 - 30 600 - 800 5 - 10 Salt 30 - 35 2000 - 2250 1 - 5

Table 1.1: Common dry bulk materials and their main properties [10]

1.1.2 Markets

The location for supply and demand of different bulk solid materials often do not coincide. For example in the coal market, the largest suppliers are Indonesia, Australia and Russia, while the largest consumers are China, Japan and South Korea, as can be seen in Table 1.2. Another ex-ample is the iron ore market. The largest iron ore suppliers are Australia, Brazil and India, while the largest consumers are China, Europe and Japan, as can be seen in Table 1.3. As a conse-quence, large scale transport is needed between suppliers and consumers of the different bulk solid materials.

Top 3 coal exporters Top 3 coal importers

Supply [M T ] Demand [M T ]

Indonesia 309 China 190

Australia 284 Japan 175

Russia 124 South Korea 129

Table 1.2: Top 3 coal exporters and importers in 2011 [3]

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Top 3 iron ore exporters Top 3 iron ore importers

Supply [M T ] Demand [M T ]

Australia 414 China 642

Brazil 324 Europe 145

India 87 Japan 133

Table 1.3: Top 3 iron ore exporters and importers in 2011 [12, 14]

Figure 1.2: Typical layout of a bulk export terminal (Dalrymple Bay Coal Terminal, Australia) [5]

1.2 Large scale bulk transport

Large scale transport of bulk solid materials often occurs by ship. At the origin of the bulk solid material, bulk carriers are loaded in bulk export terminals. The bulk carriers sail to the destination where the material is unloaded in bulk import terminals. There is a distinct difference between the layout of bulk import and export terminals, as will be shown in Section 1.2.1 and 1.2.3. The properties of bulk carriers will be discussed in Section 1.2.2.

1.2.1 Bulk export terminals

Bulk export terminals are specialized for loading bulk carriers. Figure 1.2 shows a typical layout of a bulk export terminal. A buffer of bulk solid material is kept in storage on shore, to ensure that a ship can be loaded when it arrives. In most cases, stacker reclaimers (see Figure 1.3(a)) retrieve the bulk material from the storage and send the material via conveyor belts to the bulk carrier. Due to depth restrictions, the loading jetty for large ships is located several hundreds of meters in the sea. The conveyor carrying the bulk material runs over a bridge to the jetty, where the material is transferred to a loader. A bulk loader is basically a conveyor that extends to the vessels hatches and the bulk material is dumped in the holds, see Figure 1.3(b).

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(a) Stacker reclaimer [8] (b) Bulk carrier loader [9]

Figure 1.3: Bulk export terminal equipment

Type Length [m] Draft [m] DWT [T ]

Mini Bulk Carrier 100 - 130 <10 3000 - 23999

Handysize 130 - 150 10 24000 - 35000 Handymax 150 - 200 11 - 12 35000 - 50000 Supramax 150 - 200 11 - 13 50000 - 61000 Panamax 200 - 230 13 - 15 61000 - 80000 Capesize 230 - 270 17 80000 - 199000 Suezmax 230 - 270 20 125000 - 180000

Very Large Bulk Carrier >270 >20 >180000

Table 1.4: Properties of common seagoing vessels [7]

1.2.2 Bulk carriers

Bulk carriers vary in size, depending on their application. Carriers for intercontinental transport are the largest, other sea going carriers are smaller and for inland transport over water barges or small bulk ships are common. The most important properties of common seagoing carriers are summarized in Table 1.4. The final destination of the bulk solid material often cannot receive the large seagoing vessels, because of depth restrictions of the harbor. Therefore bulk material is transshipped to smaller vessels for inland transport in bulk import terminals.

1.2.3 Bulk import terminals

Bulk import terminals have a distinctly different layout than bulk export terminals. For unloading bulk carriers, heavier equipment is used and thus a strong quay is required instead of a jetty to support the weight of the unloaders. A typical layout of a bulk import terminal is shown in Figure 1.4. Bulk unloaders, either continuous or grab type unloaders, take the bulk material from the hatches of the vessel and transfer it onto conveyors. The conveyors take the material to stacker reclaimers, which dump the bulk material onto piles in the storage. By looking at several large bulk import terminals around the world, it can be said that grab type unloaders are most common. Two types of grab unloaders can be seen in Figure 1.5, Figure 1.5(a) shows a lemniscate crane and Figure 1.5(b) shows a bridge unloader. The two cranes are different in their movements, but the operation of the grab is similar with both cranes. The grab is the actual part of the unloader

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Figure 1.4: Typical layout of a bulk import terminal (Europees Massagoed- en Overslagbedrijf, The Netherlands) [5]

that is in contact with the bulk material. Two types of grabs are common: the scissors grab and the clamshell grab. These grabs are shown in Figure 1.6. Both grabs perform well with a wide range of bulk materials, but the scissors grab has limited vertical movement of the grab shells while closing or opening. This is an advantage when clearing material from the bottom of the holds [11]. As presented in Section 1.1.1, different bulk materials have different densities. To prevent overload on the unloader, but to be close to the maximum working load as well, different sizes of grabs are used for different types of bulk material.

1.3 Problem definition

The grabs fulfill an important role in bulk import terminals. Due to the direct contact with differ-ent bulk materials and shocks during operation, grabs are susceptible to extensive wear. To obtain practical data for this research, the situation at Europees Massagoed- en Overslagbedrijf (EMO) will be investigated. From practice at EMO, a grab can breakdown due to wear on the clamshells and due to wear of the closing wires in the grab. Wear in the clamshells is visible before the grab breaks down, and can be fixed in time. Wear in the closing wires occurs suddenly, which can lead to delays during unloading, because the grab cannot be used until it is fixed. To prevent long down times during unloading, spare grabs are available in case of a grab breakdown. These are located on the quay. The storage location of the grabs on the quay mainly determines the delays due to changing a grab after grab breakdown.

1.3.1 Goal of this research

In this research, the present grab handling process at EMO is investigated to determine the time lost by grab changes after a grab breakdown. Other concepts are proposed and investigated, in

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(a) Lemniscate crane [1] (b) Bridge type crane [4]

Figure 1.5: Two types of grab type unloaders

(a) Scissors grab (b) Clamshell grab

Figure 1.6: Two types of grabs for coal and iron ore [11]

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order to find a better storage solution for the grabs and spare grabs and reduce the delays during unloading. This will be performed with a detailed calculation sheet of the unloading process.

1.4 Report overview

A graphical overview of the contents of this report is given in Figure 1.7.

Introduction

• Bulk materials

• Large scale bulk transport • Problem definition

Situation at EMO

• Unloading at the EMO terminal • Grab handling process • Data analysis

Calculation sheet of unloading

• Description of the calculation sheet • Parameters

• Output for the present situation at EMO • Verification of the calculation sheet

Two cranes on two berths

• Concepts

• Time consumption of concepts • Limitations

• Best concept

Three cranes on two berths

• Concepts

• Time consumption of concepts • Best concept

Conclusions and recommendations

• Conclusions • Recommendations

Figure 1.7: Graphical overview of report contents

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Chapter 2

Situation at EMO

This chapter gives an overview of the unloading process at EMO, the process of grab handling and an analysis of the data obtained from EMO. Section 2.1 gives an introduction to EMO, the layout of the terminal, the unloading process and grab breakdowns at EMO. Section 2.2 gives an exact overview of all the grab actions during unloading, grab breakdown and grab relocation on the quay. In Section 2.3, a statistical analysis is performed of the data obtained from EMO, to create a representative data set of the EMO terminal.

2.1 Unloading at the EMO terminal

For this research, the present situation at Europees Massagoed- Overslagbedrijf (EMO) is evalu-ated. The EMO terminal mainly handles two types of bulk material, iron ore and coal. Common vessels at the EMO terminal are Panamax (61.000-80.000 tons) and Capesize (80.000-199.000 tons).

2.1.1 Layout of the terminal

The typical layout of a bulk import terminal is already presented in Chapter 1, in the further coarse of this research, the focus will be on the unloader section of the bulk import terminal. At EMO this section consists of a quay of 1275m with 4 unloaders (Dutch: Brug 1 to Brug 4, in short BR1 to BR4) and 4 berths. BR1 and BR2 have a capacity of 50 tons, Br3 and BR4 have a capacity of 85 tons. The first stockpile (T1) of the storage is located between the supports of the unloaders. This stockpile is used for the storage of grabs and equipment, and functions as emergency bulk material storage in case the capacity of the conveyors or the other stockpiles is insufficient due to breakdowns. In that case, grabs stored on the quay need to be relocated to a safe location, away from the bulk material. This can be a time consuming and therefore expensive operation. An overview of the EMO terminal is given in Figure 2.1. BR1 to BR4 are the unloaders, present in the current situation. Unloader BR5 is added in 2013. As can be seen in the figure, the location of stockpile 1 (T1) is underneath the unloaders. The other stockpiles are connected to the unloaders via conveyors.

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Figure 2.1: Unloader section of the EMO terminal [6]

2.1.2 Unloading process

In most cases at EMO, a bulk carrier is unloaded with two cranes. BR1 and BR2 work as a pair on berth 1 and 2, while BR3 and BR4 work as a pair on berth 3 and 4. Therefore the unloading quay can be split up into two sections, both with two unloaders on two berths. When a bulk carrier is being unloaded at one berth, a second ship can already be moored at the second berth. If the first ship is finished unloading, the pair of cranes moves to the second vessel and vice versa. If the second vessel carries a different type of bulk material, the grab is changed to a grab appropriate for the type of bulk material that needs unloading. In order to minimize delays if a grab breaks down, both cranes carry the grab needed and the matching spare grab with them to the next berth.

2.1.3 Grab breakdown

Each pair of cranes has at least 4 grabs for iron ore and 4 grabs for coal. This is due to regular breakdowns of the grabs, from practical data at EMO typically 1 or 2 breakdowns per vessel. The main cause of a breakdown is a worn or even broken closing cable in the grab, which results in a grab that does not close properly and thus spilling of the bulk material. In the event of a grab breakdown, the grab is replaced with a spare. To prevent long downtime due to a grab breakdown, the unloaders carry both the grab type needed and its spare to the vessel to be unloaded, and place it halfway at the berth, at midships. In practice, a broken grab can be fixed within one hour by 3 technicians of EMO.

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2.2 Grab handling process

During unloading of bulk carriers, there are different situations where grab handling is needed. In ideal circumstances, cranes unload vessels continuously without breaking down. However, breakdowns happen regularly as will be shown in Section 2.3. To minimize delays during oper-ation, the distance that a crane travels and the number of grab handlings should be kept as low as possible. With a maximum crane speed of 25 m/min, travelling the length of a berth costs at least 12 minutes and (de-)coupling a grab costs 5 minutes. In this research, three situations are identified:

• Unloading of vessels • Grab breakdown

• Relocating grabs on the quay

In the following sections, each situation will be explained according to the present operation method at EMO.

2.2.1 Unloading of vessels

The exact process of unloading a bulk carrier is shown in Figure 2.2. There are two starting points, the first starting point is used if the next vessel requires a different type of grab, the second starting point is used if the same grab can be used. The general structure is build of pairs of a crane driving action and a grab action (coupling or decoupling). If a grab change between vessels is required, the crane moves to the location where it can store its grab and decouples it. Then the crane drives towards the required grab for the next vessel and couples it. The next action is a consequence of the working method at EMO, the crane drives to the spare grab it may need during unloading, couples it to its closing cables, drives to the midships of the bulk carrier to be unloaded and decouples the spare grab. Finally, the loop at the end of the scheme represents the actual unloading of the holds of the ship. When all holds are cleared, the process of unloading a ship ends and starts over with the arrival of the next bulk carrier.

2.2.2 Grab breakdown

Grab breakdowns occur on a regular basis, as will be shown in Section 2.3. That is the main reason why cranes at EMO carry their spare grab with them to the bulk carrier they are unloading. If the grab breaks down, the lost time will be kept minimal. Changing a grab at a breakdown is integrated as a subprocess in the unloading process in Figure 2.2. Again the structure of the process is build up of pairs of driving and a grab action. In case of a breakdown, the crane drives to a location on the quay where there is enough space to repair the grab and places the grab on the quay. Then the crane drives to its spare grab, located midships, couples the grab and drives back to the hold to continue unloading.

2.2.3 Relocating grabs on the quay

At times it can occur that the conveyors at the terminal are occupied, while a bulk carrier needs to be unloaded. To prevent long waiting times for the vessel, EMO has a stockpile located between the supports of the cranes, called T1 (see Appendix A). To use T1, all grabs on the quay must be

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Changing grab

Moving spare grab

Unloading vessel

Drive to hatch to be unloaded

Detach spare grab Drive to target spare

grab

Attach target spare grab to closing cables Drive to midships of vessel to be unloaded Start unloading new vessel

Drive to grab storage

Drive to target grab Attach target grab

Unload hatch Finish unloading Yes Detach grab All hatches unloaded? No Grab

breakdown? Yes Drive to grab storage Detach grab

Drive to spare grab Attach spare grab

Hatch empty? No Yes No Right grab attached? No Move spare grab? Yes No Yes

Figure 2.2: Process of unloading a bulk carrier 15

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Store current grab

Grab relocation

Re-attach current grab

Relocation of grabs needed

Drive to grab

storage location Detach grab

Drive to grab to be relocated Attach grab Drive to grab storage location Detach grab All grabs relocated? No

Drive to target grab

Yes

Attach target grab

Drive to unloading location

Continue unloading

Figure 2.3: Process of relocating grabs on the quay 16

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stored in a safe location away from the bulk material to be stored on T1. If the grabs are spread over the quay, it is a costly operation to move them, both in time and in money. This is illustrated in the overview of Figure 2.3. Before a crane can begin moving grabs on the quay, it has to store its grab. The loop that follows is executed for every grab that needs to be relocated. It consists of driving to the grab, coupling it, driving to the storage location and decoupling the grab. When all grabs are moved, the crane drives back to its original grab, couples it, drives back to the hold and continues unloading. In practice, this relocation cycle can be made more efficient by relocating two grabs at each time. The second grab is attached to the crane in the same way as the spare grab is attached in Section 2.2.1. By using that method, some driving time is saved.

2.3 Data analysis

EMO has extensive log files of the performed grab changes. For this research, the grab change data from 2010 will be used, among with the wire rope replacement data sheets of 2009-2010. The latter is used to check the accuracy of the first data set. In 2009-2010 a total of 349 grab changes were performed, with 176 grab changes for unloader 1 and 2 (BR1+2), and 173 grab changes for unloader 3 and 4 (BR3+4). The grab change times range from -2 minutes to 195 minutes, which shows that the data set is not very accurate. To create a workable data set, a statis-tical analysis with α = 0.05 is performed to determine the outliers of the data set. This analysis is performed for each pair of unloaders, BR1+2 and BR3+4. The results of the statistical analysis are shown in Table 2.1. As can be seen in the table, the number of vessels unloaded remains the same, while the number of grab changes decreases after the statistical analysis. Therefore the average number of grab changes per vessel decreases as well. Note that the data set contains only these vessels where a grab change is performed. Vessels without grab breakdown during unloading are not registered in the data set, but with approximately 1.5 breakdowns per vessel it is assumed that most vessels are included in the data set. Because the statistical analysis removes mostly the high outliers, as is shown in Figure 2.4, the average grab change time decreases sub-stantially. Grab changes are caused by broken closing wires. To further check the grab change data, it is compared to the number of wire replacements. An overview of this comparison is given in Table 2.2. The table shows a difference between the number of grab changes and the number of wire replacements, both before and after the statistical analysis. This is caused by the fact that in some cases more than one wire is replaced after a grab change. Exact data is not available of those cases. For the further coarse of this research, it is assumed that the filtered data set is representative for the EMO terminal.

BR1+2 all BR1+2 filtered BR3+4 all BR3+4 filtered

Vessels unloaded 126 126 115 115

Grab changes 169 161 170 162

Average grab changes per vessel 1.3 1.3 1.5 1.4

Average unloading time [hr:min] 57:48 57:48 60:41 60:41

Average grab change time [hr:min] 0:19 0:15 0:25 0:21

time as percentage of unloading 0.71% 0.56% 1.03% 0.81%

Table 2.1: Data set of 2009-2010 before and after statistical analysis

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Figure 2.4: Outliers of the data sets of BR1+2 and BR3+4

BR1+2 all BR1+2 filtered BR3+4 all BR3+4 filtered

Grab changes 169 161 170 162

Wire replacements 189 189 211 211

Difference 13 28 38 49

difference as percentage 8% 17% 22% 30%

Table 2.2: Data set of 2009-2010 before and after statistical analysis compared to wire replace-ments

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2.4 Summary

In this chapter an overview is given of the unloading process at EMO, with a focus on grab handling. For this report, the quay of EMO is divided in two sections each with two berths and two cranes. The following chapters will focus on the section with berth 3 and 4 and two 85 tons unloaders (BR3 and BR4). The unloading process is described and the influence of a grab breakdown is analysed. For the current situation at EMO, unloaders carry a spare grab to the midships of the vessel that needs unloading. In case of a grab breakdown, the unloader travels to its spare grab and exchanges it for the broken one. The broken grab will be fixed on the location on the quay where the unloader decoupled it. Between vessels carrying different types of bulk material, a change of the main grab is required to prevent too heavy or too light loads on the crane. At EMO, the grabs are stored randomly along the length of the quay on T1. In case storage on T1 is required, the grabs have to be moved to a safe location away from the bulk material. In order to determine the impact of grab breakdowns on the unloading process, operational data from EMO is used. This data contains delays during unloading of vessels due to a grab change after a grab breakdown. Because the data points in this set are spread over a wide range, a statistical analysis is performed to exclude the outliers. The filtered data set is cross checked with closing wire data and assumed to be representative for the EMO terminal.

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Chapter 3

Calculation sheet of the unloading

process

In this chapter a calculation sheet is created and evaluated using the data set from EMO. In the next chapters, this sheet will be used to analyse new concepts for grab handling. Section 3.1 describes the details of the calculation sheet. The input parameters are discussed in Section 3.2 and the output of the sheet is presented in Section 3.3. In Section 3.4, the values of the output are compared with the data set from EMO.

3.1 Description of the calculation sheet

For the analysis of the time consumption of different subfunctions during grab handling, a cal-culation sheet is created in the form of a spreadsheet. The structure of the sheet follows the structure of the scheme introduced in the previous chapter in Figure 2.2. It is divided in three sections: change grab, move spare grab and unload vessel. Each section consist of a sequence of grab handling times and driving times. The calculation sheet is presented in Figure 3.1. The goal of the sheet is to calculate the time consumption of different subfunctions of grab handling per vessel. Driving times are calculated with the average speed of the crane and the driving distance. Actual handling of the grab, such as coupling and decoupling, is determined by an activities. Three activities are defined:

1. coupling or decoupling the grab

2. coupling or decoupling the grab with boom lift action

3. coupling or decoupling the grab with waiting time for grab transport

The relevance of including time for boom lift actions and waiting for grab transport will be further explained in Chapter 4. At the end of each section, the total time of the section is multiplied by the number of times it occurs during unloading of one vessel. At the bottom of the sheet, the total time consumed by grab actions is calculated by adding all sections and subtracting the time that a crane needs to move one berth length. Due to this subtraction, the outcome of the calculation sheet is the actual time needed for grab handling only.

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distance [m] activity code duration [min] distance [m] activity code duration [min] Drive to storage 0,0 0,0 Detach grab 0,0 0,0 Drive to grab 0,0 0,0 Attach grab 0,0 0,0 Drive to hatch 0,0 0,0 Frequency [-] 0,0 0,0 Drive to grab 0,0 0,0 Attach grab 0,0 0,0 Drive to storage 0,0 0,0 Detach grab 0,0 0,0 Drive to hatch 0,0 0,0 Frequency [-] 0,0 0,0 Drive to storage 0,0 0,0 Detach grab 0,0 0,0 Drive to grab 0,0 0,0 Attach grab 0,0 0,0 Drive to hatch 0,0 0,0 Frequency [-] 0,0 0,0 Subtotal 0,0 0,0

Standard crane move 0,0 0,0

Total grab actions 0,0 0,0

Without grab change With grab change

C h an ge g ra b M o ve s p ar e Un lo ad v e ss el

Figure 3.1: Calculation sheet of unloading a bulk carrier

3.2 Parameters

Several parameters influence the outcome of the calculation sheet. An overview of these param-eters is given in Table 3.1. The quay length and number of berths determine the berth length that is used in the calculation sheet. The average gantry speed is used to convert driving distances to times. This speed is actually lower than the maximum driving speed, because of the short driv-ing distances and acceleratdriv-ing and deceleratdriv-ing. The (de-)couple time, boom lift time and grab mover response time determine the duration of each grab action. All parameters but the gantry movement between grabs and the grab mover response time are based on data provided by EMO. The gantry movement between to grabs positioned next to each other is estimated to be 15 m on average, based on the width of the grabs. The grab mover response time is estimated by adding 2 (de-)coupling actions and 5 minutes response/driving time at 10 km/h.

3.3 Output for the present situation

With the parameters as defined in Section 3.2, the calculations are performed for the present situation. The distance between a crane and its spare grab is at the present situation on average a quarter of a berth length, because the spare grabs are moved to the midships of the berth. No boom lift or grab mover are needed in case of a grab change, so only (de-)coupling times are used. The spreadsheet section ”unload vessel” is multiplied by the number of grab defects. The calculation sheet for the present situation is presented in Figure 3.2.

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Parameter Value Unit

Quay length 640 m

Number of berths 2

Gantry speed 16 m/min

Gantry movement between grabs 15 m

(De-)couple time 5 min

Boom lift time 5.4 min

Grab mover response time 15 min

Number of grab defects per vessel 1.4

Table 3.1: Input parameters for the calculation sheet, for details see Section 3.2

distance [m] activity code duration [min] distance [m] activity code duration [min]

Drive to storage 0,0 80 5,0 Detach grab 0,0 1 5,0 Drive to grab 0,0 15 0,9 Attach grab 0,0 1 5,0 Drive to hatch 0,0 0,0 Frequency [-] 0 0,0 1 15,9 Drive to grab 80 5,0 15 0,9 Attach grab 1 5,0 1 5,0 Drive to storage 320 20,0 320 20,0 Detach grab 1 5,0 1 5,0 Drive to hatch 80 5,0 80 5,0 Frequency [-] 1 40,0 1 35,9 Drive to storage 80 5,0 80 5,0 Detach grab 1 5,0 1 5,0 Drive to grab 15 0,9 15 0,9 Attach grab 1 5,0 1 5,0 Drive to hatch 80 5,0 80 5,0 Frequency [-] 1,4 29,3 1,4 29,3 Subtotal 69,3 81,2

Standard crane move 320 20,0 320 20,0

Total grab actions 49,3 61,2

Without grab change With grab change

C h an ge g ra b M o ve s p ar e Un lo ad v e ss e l

Figure 3.2: Calculation sheet of the present situation at EMO

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3.4 Verification of the calculation sheet

To compare the output of the calculation sheet with the data provided by EMO, only the section ”unload vessel” can be used. The delays due to grab actions, other than during unloading of a ves-sel, are not available. However, if the output of the section ”unload vessel” shows no significant differences with the data provided by EMO, then it can be assumed that the output of the other two sections is valid as well, because the method used and the magnitude of the input are compa-rable. The output of section ”unload vessel” is 29.3 minutes for 1.4 grab change, see Figure 3.2. This results in a grab change time of 20.9 minutes per grab change. Compared to the 21 minutes from the data from EMO (see BR3+4 filtered in Table 2.1), it can be concluded that the input used for the calculation sheet is correct for the operations needed for grab changes. While there are no significant differences between driving distances and grab changes for the section ”unloading vessel” and the other sections, it is concluded that the entire calculation sheet is representative for the situation in reality.

3.5 Summary

In this chapter, a calculation sheet is developed to analyse the subfunctions of grab handling in detail. This calculation sheet will be used later in this report to compare the delays due to grab handling between several new concepts. The consists of several subsequent driving and grab handling actions, following the scheme in Figure 2.2 of the previous chapter. Most parameters used in the calculation sheet are derived from the situation at EMO. With these input parameters, an analysis is performed on the present situation. To check if the calculation sheet represents the situation in practice, the output is compared to the filtered data set from the previous chapter. No significant differences appeared, so it is concluded that the output of the data set represents the situation in practice.

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Chapter 4

Grab handling with two cranes on

two berths

In this chapter, the situation with two unloaders on two berths will be discussed. This is the same scenario as the present situation at EMO. In Section 4.1, new concepts for grab storage on the quay will be proposed in order to reduce delays due to grab handling. In Section 4.2, the grab handling times for the different concepts will be calculated using the calculation sheet presented in Chapter 3. Time consumption is not the only restriction for determining the best concept, therefore other limitations will be discussed in Section 4.3. In Section 4.4, the different criteria will be compared in a multi criteria analysis, and the best concept will be chosen.

4.1 Concepts

The concepts in this section are based on minimizing delays due to crane travel or grab handling actions, compared to the present situation at EMO. Figure 2.2 and 2.3 are used to identify subpro-cesses of unloading where crane travel or grab actions can be reduced. At each concept, normal crane operation with grab breakdowns and relocation of grabs due to storage on T1 will be dis-cussed. Every concept is clarified with a picture, where the two types of grabs are drawn in red and green and a shielded storage as a grey box with blue boundary.

4.1.1 Deposit grabs random at the quay

This concept is similar to the present situation at EMO. With this concept all the grabs are located randomly along the quay. When a grab is no longer needed, it is placed on the nearest open spot on T1. The difference with the present situation is the fact that the spare grabs are not moved when the cranes travel between vessels. This concept is illustrated in Figure 4.1.

Normal operation

If a grab change is needed between two vessels, no extra travel time is needed for a grab change between vessels. When travelling between berths, the crane exchanges grabs when it passes the right grab.

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In this concept, the spare grab is not brought to the vessel that is unloaded. Because of the large number of grabs stored along the quay, there should always be a right type of spare grab near the vessel if needed. The time needed for moving spare grabs is therefore minimized.

If a grab change is needed due to grab breakdown, the crane detaches the grab on the nearest open spot on T1. Then the crane travels to the nearest grab of the type needed, attaches it and drives to the hatch that needs unloading.

Relocating grabs

A problem can occur when the storage capacity of T1 is needed. Because the grabs are located randomly along the entire length of the quay, grabs need to be relocated before bulk material can be stored at T1.

Figure 4.1: Grabs stored random along the quay

4.1.2 Grab storage on the crane

The concept of storing grabs on the crane instead of on the quay reduces the number of grab actions as well as crane travel during operation of the crane. For this concept to work, the cranes need to be adapted, so that the grabs can be stored on the structure of the crane. In this section, the reduction of time of this concept will be discussed. This concept is illustrated in Figure 4.2. Normal operation

If a grab change is required between vessels, no extra travel time is needed to the location of the new grab. Only delays due to decoupling and coupling grabs need to be taken into account. When the grabs are stored on the crane, moving spare grabs to the new location of the crane is no longer needed.

If a grab breaks down during unloading, the spare grab is on the crane, so again travel time is saved and only (de-)coupling time needs to be taken into account.

Relocating grabs

With this concept, grabs are no longer stored on T1. If the storage capacity of T1 is needed, bulk material can be unloaded to T1 directly, because the grabs are not on T1, but on the cranes.

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Figure 4.2: Grab storage on the crane

4.1.3 Grab storage between two berths

This concept uses special storage areas where the grabs can be stored. The storage areas are on T1, but they are shielded from the bulk material stored on T1. The storage areas are located between two berths. Spare grabs are stored in the storage areas. By doing so, the delays due to taking the spare grab to the vessel are reduced. This concept is illustrated in Figure 4.3.

Normal operation

If a grab change is required between vessels, the travel time to the new grab is minimized, because the crane passes the storage always when changing between vessels. During that change between berths, the crane stops, changes to the other type of grab and continues the travel to the next berth. Only grab change time is taken into account.

Delays due to moving the spare grab are reduced to zero, because the spare grabs are left in the storage areas.

If a grab breaks down during unloading, the spare grab needs to be retrieved from the storage area. Compared to the present situation, some extra crane travel can be needed to get the spare grab.

Relocating grabs

By using shielded storage areas for the grabs, bulk material can be directly stored on T1 if needed. No delays occur due to relocating grabs with this concept.

Figure 4.3: Shielded grab storage between berths

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4.1.4 Grab storage at midships

This concept is based on the present situation, where a spare grab is brought with the crane to the vessel that is unloaded. That spare grab is stored at midships position on the quay. In this concept, halfway each berth a shielded storage is created, with enough space for an entire set of grabs and spare grabs. Each crane takes its main grab from its ’own’ grab storage and cranes share the spare grab at the berth they are operating on. By operating this way, time is saved both for crane travel and grab actions. This concept is illustrated in Figure 4.4.

Normal operation

As for the previous concept of a grab storage between two berths, no extra travel time is needed for a grab change between vessels. With travelling between berths, the crane passes its grab storage where it can exchange the grabs.

Delays due to moving the spare grab are reduced to zero, because the spare grabs are left in the storage areas.

If a grab breaks down during unloading, the spare grab needs to be retrieved from the storage area. Compared to the present situation, the same amount of crane travel can be expected to get the spare grab.

Relocating grabs

By using shielded storage areas for the grabs, bulk material can be directly stored on T1 if needed. No delays occur due to relocating grabs with this concept.

Figure 4.4: Shielded grab storage at midships of berths

4.1.5 Grab mover and central grab storage

A totally different concept is a grab mover and a central grab storage. All the grabs are stored in a central area. This storage area does not need to be within reach of the cranes. Transport of grabs between the storage and the cranes is done with a special grab mover. This concept reduces the crane travel and grab actions. This concept is illustrated in Figure 4.5.

Normal operation

If a grab change is needed between vessels, the crane travels to its destination hatch. At that location, the right grab is brought in with the grab mover and the other grab is transported back

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to the central grab storage.

Delays due to moving the spare grab are reduced to zero, because the spare grabs are left in the storage areas. Only the response time of the grab mover has to be taken into account.

If a grab breaks down during unloading, the spare grab needs to be retrieved from the storage area. This is done by the grab exchanger, which travels faster than the crane. Although travel distances may be longer, compared to the present situation, the time needed to exchange grabs could be reduced due to the higher speed of the grab mover.

Relocating grabs

By using a special storage area outside T1 for the grabs, bulk material can be directly stored on T1 if needed. No delays occur due to relocating grabs with this concept.

Figure 4.5: Central grab storage with grab mover

4.2 Calculation sheet of the concepts

This section will evaluate the time consumption due to grab handling for the different concepts. First, different causes of delays will be discussed, secondly the input parameters for the calcula-tion sheet and third the output of the sheet for the different concepts will be given.

4.2.1 Causes of delays

Structures on the bulk carrier limit the crane in its travel due to height restrictions. The wheel-house and mast at the bow of the ship are often higher than the boom of the crane. To pass these structures, the crane has to lift its boom, which takes 5.4 minutes for the 85 tons bridge cranes at EMO (see Appendix B). This causes delays, to prevent this during the unloading of a vessel, the working area of the crane is limited to the berth length between the mast on the bow of the vessel and the wheelhouse of the vessel. This is illustrated in Figure 4.6(a). In a bulk terminal with several bridge unloaders, the unloaders travel on the same tracks. This poses the problem that cranes cannot pass each other. It limits the cranes travel to the length of the quay between the cranes on either side. This is illustrated in Figure 4.6(b).

4.2.2 Input

The time consumption of the concepts is calculated using the same calculation sheet as the present situation in Section 3.1. The concepts differ in the average distance of crane travel to the spare

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(a) Limitations on crane travel due to structures on bulk carrier

(b) Limitations on crane travel due to other cranes

Figure 4.6: Limitations on crane travel

Concept Distance to spare grab Boom lift Grab mover

Random stored 0.25 × lberth No No

Storage on crane 0 No No

Storage between berths 0.625 × lberth Yes No

Storage at midships 0.25 × lberth No No

Grab mover 0 No Yes

Table 4.1: Overview of the parameters for the different concepts

grab and grab (de-)coupling time. The latter is due to boom lift time or waiting time for the grab mover, as explained in the previous section. Table 4.1 gives an overview of these input parameters. Distances are expressed as fraction of a berth length (lberth). Both the distances of randomly stored grabs and a storage at midships are determined to be on average a quarter of the length of the berth, for two cranes working on one berth. For the concepts of a storage on the crane and a grab mover, no crane travel is required to reach the spare grab. There is however a response time of the grab mover. The distance of the storage between berths is more complicated. There are two scenarios; the grab at one crane breaks down, it travels on average a quarter of the length of the berth to reach the spare grab between berths. In the other scenario, the grab at the other crane breaks down. To reach its spare grab, this crane has to travel on average three quarters of the length of the berth and the other crane has to move a quarter of the length of the berth because cranes cannot pass each other. Assuming the change of these scenarios is equal, the average distance to the spare grab at a storage between berths is 0.625 of the length of the berth length and boom lift is required.

4.2.3 Output

The calculation sheet is evaluated for every concept described in this chapter. For details of the separate calculation sheets, see Appendix D. These sheets contain the input data as described in Table 4.1. The output consists of total grab handling times per concept, as well as grab handling times as percentage of total unloading time, both for the situation with and without grab change before unloading. The output is presented in Table 4.2. For comparison, the present situation is also included in this table. It can be concluded that multiple concepts result in considerable time

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Concept Without grab change With grab change Time [min] % of unloading Time [min] % of unloading

Present situation 49 1.35% 61 1.68%

Random stored 29 0.80% 40 1.10%

Storage on crane 14 0.38% 24 0.66%

Storage between berths 65 1.79% 76 2.09%

Storage at midships 29 0.80% 40 1.10%

Grab mover 28 0.77% 38 1.04%

Table 4.2: Overview of the output for the different concepts

savings. Note that several concepts still save time with a grab change, compared to the present situation without grab change.

4.3 Limitations

Time savings are not the only factor for determining the best concept for grab handling. A number of limitations have to be taken into account. These limitations pose restrictions for the position of the grab storage on the quay, due to limited reach of the crane during operation. The limitations are the number of grabs available, the storage capacity of T1 and the safe working regulations. All these restrictions will be discussed in this section.

4.3.1 Number of grabs

The number of grabs can become a restriction in the design of a new grab storage when there are few available. If there is only one spare grab of each type, the spare grab has to be moved between vessels in order to limit the delays in case of a grab breakdown. If one spare grab is available per berth, that spare grab can be stored at its berth and cranes can share that spare grab. If more spare grabs are available per berth, cranes do not have to move or share the spare grab.

4.3.2 Storage capacity of T1

As stated in previous chapters, the space underneath the cranes is not only used for the storage of grabs, but for storage of bulk material as well. Due to this storage of bulk material, it can happen that spare grabs need to be relocated to keep them separated from the bulk material. This could be a time consuming operation if several grabs need to be relocated. In case of other types of grab storage, the area used for storing the grabs can no longer be used for the bulk material and reduces the capacity of T1 and thus of the entire terminal. To minimize the loss of capacity, the storage should be as compact as possible. This is illustrated in Figure ??.

4.3.3 Safe working regulations

Working with heavy loads and on heights is regulated by laws and by company rules as well [2, 6, 13]. In the regulations for heavy loads is stated that a hanging load or unsecured load at height may never be above an area where people may come. The Dutch law for working at

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heights applies to every working situation at 2.5 meters or higher. If the situation is determined to be at height, special safety precautions should be made, such as safe walkways with handrails and personal fall protection gear.

4.3.4 Cost

Another decision factor is the cost of the concept. The cost are divided in a initial investment and the running cost. The initial investment is used to realize the concept, and it consists of engineering, fabrication and installing. The running cost are used to operate the concept, they consist of manpower, fuel and maintenance.

4.4 Best concept

The best concept is chosen, using a multi criteria analysis with the output of the calculation sheets and the limitations. For comparison, the present situation is included as well. First, the concepts are rated according to a method suitable for the different times or limitations in Table 4.3. The grab handling times are determined by the output of the calculation sheets, as presented in Table 4.2. The number of grabs needed follows the description of the concepts, as presented in Section 4.1. The other criteria are harder to compare, because of the differences between concepts. Therefore, these criteria will not be assigned a value, but a score from - - to ++, where - - is negative and ++ is positive. With the concept of a grab mover, no capacity of T1 is lost, so it gets ++. In the present situation, randomly stored grabs and a shielded grab storage at midships or between berths, some area of T1 is required for grab storage. Because this area is minimal, these concepts get +. A grab storage on the crane reduces the width of the stockpile on T1 over its entire length, reducing the capacity drastically. Therefore the grab storage on the crane gets a - on this criterium. In case T1 is needed for storage, the grabs on the quay need to be located safe from the bulk material. In all concepts, except for the present situation and randomly stored grabs, the grabs are shielded from the bulk material when stored. These concepts get ++, while the concepts that need relocation of grabs get - -. Regulations is a criterium that is a collection of safety rules, such as working on heights and working under a suspended load. Every grab (de-)couple is regarded as working on heights, while working under a crane in operation (for example while repairing a grab)is regarded as working under a suspended load. The less of these actions means a better rating of this criterium for the concept. The present situation and randomly stored grabs require only the minimum of one decoupling and one coupling action to replace a grab. While replacing, the broken grab is located on a safe working location for repairs. However, when grabs need relocation, an extensive amount of (de-)coupling grabs is required. These concepts get 0. The shielded grab storage between berths or at midships is comparable to the previous concepts, only no grab relocation is required. Therefore these concepts get ++. With a grab storage on the crane, replacing a grab is not only working on heights, but also working on a crane in operation. Furthermore, a broken grab is repaired on the quay, so extra grab handling is required. This concepts gets -. The last concept, the grab mover requires three times as much grab (de-)coupling actions as the present situation. The grabs are repaired well out of reach of the cranes, so this concept gets -. The last criterium, as discussed in Section 4.3, consist of two parts: initial cost and operating cost. The present situation and randomly stored grabs have no initial cost and no extra maintenance or personnel cost, therefore getting 0. A wall needs to be built to create a shielded grab storage between berths or at midships, but no extra operational cost is required.

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This results in a slightly worse rating than the previous concepts, resulting in -. A grab storage on the crane requires engineering and fabrication to adapt the crane, resulting in very high initial cost. Operational cost does not increase compared to the present situation, this concept get - -. The grab mover requires high initial cost and extra personnel for operation, so this concept gets - - as well. These ratings are converted to a standardized scale. For the grab handling time and number of grabs, a linear relationship is assumed between the worst and best value. Interpolating yields the standardized values. For grab handling time, no delay (0 minutes) is the best value, the highest time of the concept is the worst value. In case of two cranes, two grabs required is the best case. Four grabs for two cranes is chosen to be average, so six grabs is the worst value. The other criteria are rated using - - to ++, where - - represents 0, - is 0.25, 0 means 0.5 in the standardized scale, + is 0.75 and ++ represents 1. These standardized values are assigned more weight if the property is more important in Table 4.4. The concept with the highest overall score is chosen to be the best concept. Time and cost are weighted twice as heavy as the rest of the criteria, because they have direct impact on the daily performance of the terminal, where the rest of the criteria has less impact. The concept that proves to be the best is a shielded grab storage at the midships of every berth, followed by a central grab storage with grab mover.

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Unit Present situation Random stored Storage on crane Storage between berths Storage at midships Grab mo v er Grab handling time min. 49 29 14 65 29 28 Number of grabs 4 4 4 3 4 3 Capacity of T1 ++/ -+ + -+ + ++ Grab relocation ++/ -++ ++ ++ ++ Re gulations ++/ -0 0 -++ ++ -Cost ++/ -0 0 -T able 4.3: Rating for the dif ferent concepts and limitations, for details see Section 4.4 W eight Present situation Random stored Storage on crane Storage between berths Storage at midships Grab mo v er Grab handling time 2 0.24 0.55 0.78 0 0.55 0.57 Number of grabs 1 0.5 0.5 0.5 0.75 0.5 0.75 Capacity of T1 1 0.75 0.75 0.25 0.75 0.75 1 Grab relocation 1 0 0 1 1 1 1 Re gulations 1 0.5 0.5 0.25 1 1 0.25 Cost 2 0.5 0.5 0 0.25 0.25 0 W eighted av erage 0.40 0.48 0.45 0.50 0.61 0.52 T able 4.4: Standardized multi criteria analysis for the dif ferent concepts 33

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4.5 Summary

In this chapter five concepts for grab handling are proposed:

• Randomly store grabs on the quay, without taking spare grabs to the vessel • Grab storage on the back supports of the unloader

• Shielded grab storage between two berths

• Shielded grab storage at the midships of every berth • Central grab storage with a grab mover

The aim of the concepts is to reduce the number of grab actions and the travel distance of the crane to the spare grabs, thus reducing the delays due to grab handling during unloading. In contrast to the present situation, none of the concepts takes the spare grab with the unloader to the next vessel. Most concepts do not need relocation of the grabs in case storage on T1 is needed. Table 4.5 gives an overview of these aspects. To determine the delays per concept, the same calculation sheet is used as in the previous chapter. For the determination of the best concept, not only reduction of delays is analysed, but other limitations as well. These limitations are the number of grabs needed, reduction of storage capacity on T1, safe working regulations and cost. The concepts are compared using a multi criteria analysis. For comparison, the present situation at EMO is included as well in this analysis. The concept that proves to be the best is the grab storage at midships, followed by the central grab storage with grab mover.

Concept Distance to spare grab Move spare grab Grab relocation

Present situation 0.25 × lberth Yes Yes

Random stored 0.25 × lberth No Yes

Storage on crane 0 No No

Storage between berths 0.25 × lberth No No

Storage at midships 0.25 × lberth No No

Grab mover 0 No No

Table 4.5: Differences between the concepts

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Chapter 5

Grab handling with three cranes on

two berths

In 2013, the situation at EMO has changed to two 50 tons unloaders (BR1 and BR2) and three 85 tons unloaders (BR3, BR4 and BR5). The expectation is that the 85 tons unloaders will be used primarily at berth 3 and 4. Then two scenarios can occur:

1. Berth 3 and 4 are both occupied; two cranes unload the bulk carrier at one berth, the third crane unloads the bulk carrier at the other berth.

2. Only one of the berths is occupied; all three cranes unload the bulk carrier at this berth. In the first case, the calculation sheets of Chapter 4 can be used. Therefore, case one will not be discussed in this chapter. The second case poses a problem, because the cranes can hinder each other in case of a grab breakdown. In case of the grab storage at midships, the outer cranes can’t reach the storage without moving the middle crane, see Figure 5.1(a)- 5.1(c).

5.1 Concepts

In this chapter, not all concepts of the previous chapter will be discussed. An adapted version of the present situation for three cranes, present situation+, and the two best concepts, the grab storage at midships and the grab mover will be evaluated for the case of three cranes at one berth. In the following sections, the influence of the third crane on these concepts will be discussed.

5.1.1 Present situation+

In Chapter 3, the present situation is evaluated. To accommodate the third crane on one berth, the calculation sheet has to be adapted. Assuming that the spare grabs will still be located at midships, a problem occurs when reaching for the spare grab. The middle crane blocks the two other cranes from the grab storage. If one of these two cranes has a grab breakdown, not only that crane, but also the middle crane has to move in order to change the grab, as can be seen in Figure 5.1(a) and 5.1(c). Due to this problem, two cranes are temporarily out of operation, resulting in higher loss of production than with only two cranes on one berth. With the present situation+, only one

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(a) Grab breakdown at crane 1; crane 2 blocks the grab storage at midships

(b) Grab breakdown at crane 2

(c) Grab breakdown at crane 3; crane 2 blocks the grab storage at midships

Figure 5.1: Effect of grab breakdown with three cranes on one berth

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spare grab is moved to the ship to be unloaded. This is done by the middle crane, because it is operating near the midships. By doing so, the number of grabs does not need to be changed. In case T1 is needed for storage, the grabs still have to be relocated as in the original situation.

5.1.2 Grab storage at midships

The concept of a grab storage at midships needs small changes to accommodate the third crane. As the present situation+, the middle crane blocks the two other cranes from the grab storage. If one of these two cranes has a grab breakdown, not only that crane, but also the middle crane has to move in order to change the grab, as can be seen in Figure 5.1(a) and 5.1(c). The number of grabs at each storage does not have to be changed. If two cranes take the appropriate grab and spare grab from the storage at the empty berth and the third crane takes a grab from the unloading berth, still one spare grab is available at the unloading berth.

5.1.3 Grab mover and central grab storage

Because cranes do not need to move with this concept in case of a grab breakdown, but instead the spare grab is brought to the crane, there is no problem that the third crane hinders the other cranes. Unlike the concept of a grab storage at midships, where 4 grabs of each type were already present, the concept of a grab mover needs an extra grab. With two cranes, two grabs and one spare grab of each type was enough. Now with the third crane, three grabs are needed and one spare grab.

5.2 Calculation sheet of the concepts

5.2.1 Assumptions

There is no data available at EMO of operation with three cranes on one berth, so some assump-tions have to be made in order to adapt the calculaassump-tions of Chapter 4:

• The number of grab breakdowns per ship remains the same as in Chapter 4. The same amount of material is unloaded with three grabs instead of two. However, the number of grab loads per ship remains approximately the same, so the wear on the grabs will also remain the same.

• With the concept of a grab storage at midships, in case a grab breakdown occurs at one of the outer cranes, the middle crane always stops unloading in order to move out of the way. • The average crane speed remains the same as in Chapter 4. Although the average distance

to the spare grabs changes, it is assumed that the average crane speed does not change.

5.2.2 Input

Due to the fact that in some cases two cranes need to move for a grab change, with the concept of the present situation+ and a grab storage at midships, the travel distance for these concepts will be longer with three cranes at one berth. This causes extra delays, which represent the extra loss of production. The rest remains the same as Chapter 4. See Table 5.1 for an overview of the input. As explained in the previous section, the average distance to the spare grab increases

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Concept Distance to spare grab Boom lift Grab mover

Present situation+ 0.33 × berthlength No No

Storage at midships 0.33 × berthlength No No

Grab mover 0 No Yes

Table 5.1: Overview of the parameters for the different concepts

Concept Without grab change With grab change

Time [min] % difference Time [min] % difference

Present situation+ 43 +0% 55 +0%

Storage at midships 33 -0.27% 44 -0.30%

Grab mover 28 -0.41% 38 -0.47%

Table 5.2: Overview of the output for the different concepts

due to the third crane. The average distance of the middle crane to the spare grab is zero meters. The average distance of the two other cranes to the spare grab is 0.33 × berthlength and the movement of the middle crane is 0.165 × berthlength. The average distance of all three cranes is

0.33 + 0.165 + 0 + 0.33 + 0.165

3 = 0.33 × berthlength

5.2.3 Output

The calculation sheet is adapted and evaluated for the two best concepts of the previous chapter. For details of the separate calculation sheets, see Appendix E. These sheets contain the input data as described in Table 5.1. The output for the calculation sheets of three unloaders working on one berth is presented in Table 5.2. There is no practical data of unloading times with three cranes per vessel. Therefore grab handling times cannot be compared as a percentage of the unloading times. Therefore the output consists of grab handling times in minutes and as a percentage compared to the present situation+.

5.3 Best concept

As in Chapter 4, the best concept is chosen using a multi criteria analysis with the output of the calculation sheets and the limitations. The concepts are again rated according to a method suitable for the different times or limitations in Table 5.3. Because only a few items are changed for three cranes on two berths, most values remain the same as in Table 4.3. Then these values are converted to a standardized scale and assigned more weight if the property is more important in Table 5.4. The concept with the highest overall score is chosen to be the best concept. The concept that proves to be the best again is the shielded grab storage at the midships of every berth, followed by a central grab storage with grab mover.

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Unit Present situation+ Storage at midships Grab mover

Grab handling time min. 43 33 28

Number of grabs 4 4 4

Capacity of T1 ++/- - + + ++

Grab relocation ++/- - - - ++ ++

Regulations ++/- - 0 ++

-Cost ++/- - 0 -

-Table 5.3: Rating for the different concepts and limitations

Weight Present situation+ Storage at midships Grab mover

Grab handling time 2 0 0.23 0.35

Number of grabs 1 0.5 0.5 0.5 Capacity of T1 1 0.75 0.75 1 Grab relocation 1 0 1 1 Regulations 1 0.5 1 0.25 Cost 2 0.5 0.25 0 Weighted average 0.34 0.53 0.43

Table 5.4: Standardized multi criteria analysis for the different concepts

5.4 Summary

In this chapter, the new situation with three unloaders at berth 3 and 4 of EMO is evaluated. In case two unloaders are working at one berth and the third at the other berth, the outcome of the previous chapter can be used. When three unloaders are working on the same berth, a situation is created where unloaders block each other from reaching the grab storage. Therefore a new analysis is performed for this new situation. Not all concepts are included in this analysis, only the grab storage at midships and the central grab storage with grab mover. For comparison, an adapted version of the present situation to accommodate three unloaders is included as well. Because no practical data is available, this analysis cannot be compared to the situation in reality. For the analysis of delays due to grab changes, the same calculation sheet is used as in the previous chapters. The grab mover needs an extra grab, compared to the situation with two unloaders, the rest of the other limitations remains the same for all concepts. Again a multi criteria analysis is performed. The concept of a shielded grab storage at midships again proves to be the best, followed by the central grab storage with grab mover.

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Grijper activiteiten in een bulk import terminal

Specialization: Transport Engineering and Logistics

Report number: 2013.TEL.7780

Title:

Grab handling activities in a bulk

import terminal

Author:

B.B. de Keyzer

Grab handling activities in a bulk import terminal

Bj¨orn de Keyzer

Transport Engineering and Logistics,

TU Delft

Contents

Chapter 1

Introduction

1.1

Bulk material

1.1.1

Properties

1.1.2

Markets

1.2

Large scale bulk transport

1.2.1

Bulk export terminals

1.2.2

Bulk carriers

1.2.3

Bulk import terminals

1.3

Problem definition

1.3.1

Goal of this research

1.4

Report overview

Chapter 2

Situation at EMO

2.1

Unloading at the EMO terminal

2.1.1

Layout of the terminal

2.1.2

Unloading process

2.1.3

Grab breakdown

2.2

Grab handling process

2.2.1

Unloading of vessels

2.2.2

Grab breakdown

2.2.3

Relocating grabs on the quay

2.3

Data analysis

2.4

Summary

Chapter 3

Calculation sheet of the unloading

process

3.1

Description of the calculation sheet

3.2

Parameters

3.3

Output for the present situation

3.4

Verification of the calculation sheet

3.5

Summary

Chapter 4

Grab handling with two cranes on

two berths

4.1

Concepts

4.1.1

Deposit grabs random at the quay

4.1.2

Grab storage on the crane

4.1.3