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 130 pages and 2 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
Specialization: Transport Engineering and Logistics Report number: 2016.TEL.7995
Title: Investigation for improvement of
the lashing process for containers on deck of seagoing container vessels.
Author: M. van der Heide
Title (in Dutch) Onderzoek naar de verbetering van het vastmaken van containers op diepzee containerschepen.
Assignment: Literature Confidential: no
Initiator (university): ir. W. van den Bos
Initiator (company): J. Stefanoff (PSA Antwerp) Supervisor: Ir. W. van den Bos
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: M. van der Heide Assignment type: Literature Supervisor (TUD): Ir. W. van den Bos Creditpoints (EC): 10
Supervisor (TUD): Prof. Dr. Ir. G. Lodewijks Specialization: TEL
Report number: 2016.TEL.7995 Confidential: no
Subject: Investigation for improvement of the lashing process for containers on deck of seagoing container vessels.
The aim of this research project is to improve the lashing procedure to fix containers to the seagoing container vessel. Currently the lashing procedure is very time consuming and even
dangerous for personnel because of the complex and non-automated procedure with heavy parts and high tension forces. The lashing process depends on several variables like the different available lashing tools, the design of the connection points on the vessel, the accessibility of the vessel etc. In this research an overview of the available lashing methods with an overview of the tools, process time etc. should be made. The different methods should be judged on relevant criteria as safety and overall required time and possible criteria for a new uniform lashing process should be proposed. The report should comply with the guidelines of the section. Details can be found on the website. The professor,
Preface
This literature study is the result of 3 months research in the field of container lashing. During these 3 months, an overview of the current lashing equipment and lashings process is made. The second part of the report is a study in the possibilities for a new lashing method.
This research is done in response to a challenge composed by PSA Antwerp in 2014. Since the introduction of standardized containers in 1955 the container ships are getting bigger and bigger, this resulted in a higher demand on the lashers employed by the ports. So PSA Antwerp wrote a challenge for innovation in lashing equipment.
I would like to thank Ir W. van den Bos (TU Delft) as my supervisor and Joeri Stefanoff (PSA Antwerp) for their time and information.
Marnix van der Heide
Delft,
Summary
Since the introduction of ISO containers in 1955, container freight has rapidly increased. This results in bigger ships and higher demands for cost efficiency. One of the boundary conditions is that the ships need to have the same tun around time in port as the previous generation. This means that more containers from a ship need to be handled in the same time by the port. Containers are lashed to the deck to withstand heavy sea conditions. These lashes are installed by employees of the terminal. This job is dangerous because of lashing equipment laying around and the harsh environment. The job is physically demanding, high tension forces and wrong posture cause many injuries each year.
Currently, containers are lashed using rods and turnbuckles. The rods are connected to the container and the turnbuckle to the ship. Rotating the turnbuckle by hand produces tension in the lashing. Lashings can be installed using the internal or external lashing method. These methods differ in the way the force travels through the container.
PSA Antwerp has written an innovation challenge to find a new and better lashing method. Internal development at PSA Antwerp has already lead to a prototype.
For the design of a new lashing method, technical demands and criteria need to be composed. The criteria will be used to judge new concepts in a multi-criteria analysis. From a study on researches and guidelines about container lashing, the following demands and criteria are com-posed.
Technical demands:
• Compatible with current lashing methods and arrangements • Compatible with all container types and sizes
• A minimum breaking force of 460kN • Usual working load 230kN
• A weight of less then 12kg
• The length is adaptable from 1.5m to 1m Criteria, the new concepts should:
• Be reliable
• Have a non complex design
• Have a Quick and easy installation method • Consist of lightweight components
• Have easy maintenance • Be cost efficient
There are four mechanisms that are currently used in other industries for lashing. The me-chanical mechanisms will probably be the best option for a new concept. The pneumatic and hydraulic have many parts that can wear out and cause the system to leak. This leakage will drop the pressure and so the tension during voyage.
List of Abbreviations
Abbreviation Description
ISO International Organization for Standardization
TEU Twenty-foot Equivalent Unit
PSA Port of Singapore Authority
ULCV Ultra Large Container Ship
QC Quay Crane
NIOSH National Institute of Occupational Safety and Health
List of Figures
1 Increase in container freight. [1] . . . 2
2 Maximum ship size by year [2] . . . 3
3 Ship sizes with section cut [3] . . . 4
4 The Ital Florida after containers stack fell over [4] . . . 4
5 Lashing bar [5] . . . 5
6 Turnbuckle type 1 [5] . . . 5
7 Turnbuckle type 2 [5] . . . 5
8 Internal vs External Lashing [6] . . . 7
9 Screw part of the prototype with the bolt on the left. . . 8
10 Lashing equipment prototype by PSA Antwerp . . . 9
11 Example of container racking. [7] . . . 11
12 The geometry of a lash in three dimensions [8] . . . 15
13 Lashing arrangements for multiple tiers [9] . . . 16
14 Lashing plate with correct and incorrect direction of force [10] . . . 17
15 Geometry of a lashing plate [11] . . . 18
16 Typical arrangement of lashing plates [5] . . . 18
17 Upper Corner Casting [5] . . . 19
18 Bottom Corner Casting [5] . . . 19
19 Weight limit per lifting height [12] . . . 20
20 Weight limit per lifting frequency [13] . . . 20
21 Average wave height. [14] . . . 25
22 The allowable forces on a 20 or 40 foot container. [6] . . . 26
23 The 6 degree’s of freedom of a ship. [15] . . . 27
24 Scale model of a container vessel in extreme head seas at Marin. [16] . . . 28
25 A 2D expression of an acceleration ellipsoid for a specific tier in container stack. [17] 29 26 Conversion from a 20ft ISO container to a scale model. [15] . . . 30
27 A 1:7 scale model of a 7 tier container stack. [15] . . . 30
28 Lasher applying pretension to the lashing equipment. [18] . . . 32
29 Static full scale tests and finite element analyses on a 20 foot container. [19] . . . 34
30 Hydraulic cylinder [20] . . . 40
31 Turnbuckle with a built in ratchet. [21] . . . 41
32 Speed lashing equipment used to secure rolling cargo. [22] . . . 42
33 A lever mechanism to secure cargo with a chain. [23] . . . 42
34 Rule of thumb to calculate minimum diameter of bending. [24] . . . 43
35 Required torque needed on the screw side. [25] . . . 44
36 Metabo SSW 18 LTX 600 battery impact wrench. [26] . . . 45
37 PneuTorque PTM-72 pneumatic torque wrench. [52] . . . 46
38 Pneumatic wrench with an open end. [27] . . . 47
39 The speed sincher, able to tighten turnbuckles on deck. [28] . . . 47
40 A lasher, tightening the lash using a steel rod. [53] . . . 48
List of Tables
1 The length of lashings [29] . . . 16
2 The allowable forces on a 20 or 40 foot container. [6] . . . 26
3 Standard racking resilience for steel frame containers. [29] . . . 34
4 Minimum and maximum gross weights of containers. [29] . . . 35
5 The wind and green water load for containers. [29] . . . 35
6 Loads for lashing equipment. [29] . . . 38
7 Minimum breaking strength and safe load for Bright wire, uncoated, fiber core wire rope, improved plow steel. [30] . . . 43
8 Properties of the Metabo SSW 18 LTX 600. [26] . . . 45
Table of contents
Preface i
Summary iii
List of Abbreviations v
List of Figures and Tables vi
1 Introduction 2
1.1 Increase in container freight . . . 2
1.2 The need for lashing . . . 4
1.3 Current lashing system . . . 5
1.3.1 Lashing equipment . . . 5
1.3.2 Material . . . 6
1.3.3 Internal and External lashing . . . 7
1.4 Problems with lashing system . . . 7
1.5 PSA Antwerp prototype . . . 8
2 Design Criteria 10 2.1 Reliability . . . 10 2.2 Simplicity . . . 11 2.3 Compatibility of equipment . . . 11 2.4 Flexibility . . . 11 2.5 Speed of use . . . 12 2.6 Ease of use . . . 12 2.7 Minimum maintenance . . . 12 2.8 Cost efficiency . . . 12 2.9 Power Consumption . . . 12 3 Specifications 14 3.1 Length . . . 15 3.1.1 Longitudinal distance . . . 17 3.1.2 Transverse distance . . . 17 3.1.3 Vertical distance . . . 17 3.2 Connections . . . 18
3.2.1 Ship lashing plate . . . 18
3.2.2 Container corner casting . . . 19
3.3 Weight . . . 20 3.4 Time . . . 21 3.5 Cost . . . 22 4 Forces 24 4.1 Pretension . . . 24 4.2 Fatigue . . . 25
4.4 Ship Motions . . . 27
5 Technical demands from the Guidelines 32 5.1 Lashing Force . . . 32
5.1.1 Deformation . . . 33
5.1.2 Racking Force . . . 34
5.2 Rules for lashing . . . 37
5.2.1 Placement . . . 37 5.2.2 Forces . . . 37 6 Design Options 40 6.1 Hydraulic . . . 40 6.1.1 External Leakage . . . 40 6.1.2 Internal Leakage . . . 40 6.2 Pneumatic . . . 41 6.3 Screw . . . 41 6.3.1 Turnbuckle . . . 41 6.3.2 Worm gear . . . 42 6.4 Lever . . . 42 6.5 Cable . . . 43 7 Power Sources 44 7.1 Torque required . . . 44
7.2 Battery Impact Wrench . . . 45
7.3 Pneumatic Torque Wrench . . . 46
7.4 Torque Wrench . . . 47
7.5 Human Power . . . 48
8 Conclusion 50
9 Recommendations 52
Bibliography 54
Appendix A - PSA Innovation Challenge 58
1
Introduction
Lashing equipment is used to secure containers on container vessels. This chapter starts with an introduction in container transport and a description of the current lashing system. In the second part, the problems of the current lashing system are stated and a possible prototype from PSA Antwerp is introduced.
1.1 Increase in container freight
Since the introduction of ISO containers in 1955, there has been an exponential growth in container freight as can be seen in figure 1. Besides a drop in the demand in 2009 as a result of the economic crisis, the container demand has been growing every year.
Figure 1: Increase in container freight. [1]
This growth also resulted in an increasing size of container ships, making container freight more profitable. In 2005, van Ham [31] did a research about the feasibility of container vessels. In 2005, the largest container vessels could carry around 8000 TEU. The development of ship sizes is illustrated in figure 2.
Figure 2: Maximum ship size by year [2]
In his paper, van Ham discussed the feasibility of the Mallaca-max vessel type. His conclu-sion was that vessels of this size would probably not be feasible. Arguments for this are mainly the limitations in engine size and availability of suitable ports.
The engine problem was solved by the ship builders by setting a lower cruising speed for the vessels. Today’s vessels have a cruising speed of 22.8 knots [32] in comparison to 25.5 knots [31] in 2004. The engine has actually stayed the same in size, around 63mW [32].
The ports followed the ship builders and adjusted so they could handle these mega vessels. This all resulted in vessels able to carry around 20.000 TEU in 2015 [32]. It is interesting to see that this complies with the expectations of van Ham made in 2005 [31].
1.2 The need for lashing
The container vessels have increased in capacity, as described in section 1.1. To see the influence of this increasing capacity on the vessels dimensions, vessels from the start of the containeriza-tion till now are in one figure 3.
Figure 3: Ship sizes with section cut [3]
The increase in stack height has an effect on the stability of the stack. With multiple containers on top of each other on the deck(up to 10), only twistlocks are not enough to keep the stack stable. Twistlocks lock two containers on top of each other but can not prevent a whole stack from tumbling over. To prevent this, diagonal lashings are needed.
1.3 Current lashing system
In this chapter, the current container lashing system is described. The current lashing systems exists for tens of years, there has not been much innovation. The first part of this chapter is about the equipment itself and the second part goes into the use of the equipment.
1.3.1 Lashing equipment
There are two lashing systems on the market, but they work the same so they will be described together. The current lashing equipment consists of two main components. The lashing bar and the turnbuckle.
The lashing bar is a long steel bar with a knob at one end. This knob is inserted in a container corner casting. On the other side of the bar there is a connection to the turnbuckle. This connection can be different depending on the lashing system.
Figure 5: Lashing bar [5]
The second part of the equipment is the turnbuckle. The turnbuckle is connected to an eye on the ship and on the other side to the lashing bar. The turnbuckle is used to adjust the length of the lash and tighten it. For both the systems the outside of the turnbuckle is rotated around a screw. An additional tool is used to tighten the lash to a desired tension.
Figure 6: Turnbuckle type 1 [5]
Figure 7: Turnbuckle type 2 [5]
1.3.2 Material
The lashing equipment is currently made out of high high tensile steel with a hot dip galvanized treatment [33]. This results in a minimum breaking load (BL) of 460kN and a usual working load (WL) of 230kN [8]. Between the breaking load and working load there is a safety factor of 2 [29].
W L = BL
sf (1)
where
W L = Usual Working Load of the equipment. [N]
BL = Breaking Load of the equipment. [N]
sf = Safety factor, usually between 2 and 2.5 for lashing equipment [29].
The exact material that is used for lashing equipment can not be found. But with the properties know, an assumption can be made.
The breaking load is 460kN, from figure 5 it can be seen that lashing rod has a diameter of 26mm. This results in a maximum pressure of 866 MPa in the rod. So we can assume that the high-strength steel S890 is used for lashing equipment.
1.3.3 Internal and External lashing
With the equipment described in previous chapter, numerous configuration can be made to secure the containers. The main configuration, used by most shipping companies is called internal lashing. A newer lashing method is external lashing, allowing higher stack weights but increases the forces in the lashings [6].
Figure 8: Internal vs External Lashing [6]
The main difference between internal and external lashing can be seen in figure 8. The internal lash has a tension force on the compression side of the container. The external lashing however has a tension force on the lifting side. This force in opposite direction reduces the stress in the container [34].
1.4 Problems with lashing system
The current lashing system has some drawbacks. These drawbacks are mainly for the employees installing the lashing equipment. These lashers are employed by the port so the ports also notice these drawbacks.
In section 1.2 an increase in container vessel size was shown. These bigger ships come at higher operational costs for the ship owners. This makes it more important that the ships are being used in the way they earn money for the ship owner. This means more days at sea and less time at the port. For the terminal they expect shorter handling times with the same equipment as 20 years ago. PSA Antwerp noticed this problem and started the ”Innovative Lashing Equipment Challenge”.
1.5 PSA Antwerp prototype
At PSA Antwerp, a prototype version of possible new lashing equipment has already been constructed. This new design is a combination of the already existing turnbuckle with a RoRo securing device (see 6.3.2). This prototype is made by welding these two components together resulting in a heavy and not optimized piece of equipment.
Figure 9: Screw part of the prototype with the bolt on the left.
On the top of this prototype there is a bolt (left side of figure 9), this bolt will drive the screw. This moves the holder for the turnbuckle along the screw. The bolt can be turned using a battery driven torque wrench which reduces the physical work by the lasher. The prototype has a weight of around 20kg compared to 12 kg of a normal turnbuckle.
Figure 10: Lashing equipment prototype by PSA Antwerp
2
Design Criteria
During the design of a new container lashing system, there should be reference criteria to judge the design alternatives. In this chapter, these criteria will be given and explained. Limitations for these criteria will be given where possible.
As a guidance, for finding these criteria, the research by Z. Radiˇsi´c [35] is used. The criteria from his research are:
• Reliability • Simplicity • Compatibility of equipment • Flexibility • Speed of use • Ease of use • Minimum maintenance • Cost efficiency
For this research the power consumption is also added. In the next part of this chapter, these nine criteria are explained.
2.1 Reliability
Reliability for lashing equipment consists of two parts. First of all, the equipment itself should not fail. The equipment should be of high enough quality for this. Also, the lashing method should be sufficient for the task.
The second point Z. Radiˇsi´c mentions in his paper is the reliability of the lashing method itself. When the containers are secured correctly, the chance on container damage should be low. Research [35] has for example shown that racking (see figure 11) of containers was a bigger issue then containers falling over. This has resulted in the abandonment of vertical lashings.
Figure 11: Example of container racking. [7]
2.2 Simplicity
The Careful to Cary Committee [36] writes that simple systems are not always the most efficient systems. But simple systems should be encouraged because they improve safety. Simple systems also allow a shorter learning time for new personnel.
2.3 Compatibility of equipment
Compatibility of lashing equipment is determined by whether the equipment is capable of lashing the containers. There are two aspect to the compatibility.
First of all, as discussed before at 2.1, the equipment should be able to withstand the loads on the system. These loads can be determined by evaluating the ships motions.
The second aspect is about the connection with the ship and container. At the ship there is usually an eye and at the container is a corner casting. The equipment should be able to connect to these points and the whole system must respect the maximum strength in these connection points.
2.4 Flexibility
Flexibility has, in this case, nothing to do with the material or construction of the lashing equipment. The equipment can either be flexible or rigid. The flexibility is in the use of the equipment, so the equipment can be used in different situations. For example when shipping different sizes of containers. Usually containers are 20 or 40 feet, if there is one longer container it is not lashed [8]. But there is also difference in height, containers can be 8, 8.5 or 9.5 feet high. The lashing equipment should be able to lash containers with different heights.
According to Z. Radiˇsi´c [35], the stowage of multiple container sizes on one ship emerged when
ship operators wanted to address a higher number of ports with one ship. This also resulted in smaller badges of containers per port. So individual containers needed to be handled without affecting the stack next to the container. This gives the last aspect of a flexible lashing system.
2.5 Speed of use
The time it takes for the lashers to secure the containers is very important for the ship owner. A container ship is a transport vessel that makes money by transporting containers from one place to another. Being moored in at a port will cost the ship owner money. Not only the moored ship will cost the ship owner money in the port, also the lashers are employees from the port. A faster lashing method will result in less labor costs. A calculation about lashing time is made in chapter 3.4.
2.6 Ease of use
The equipment should not only be simple but also easy to use for the lashers. Container lashing is a very demanding job, lashers need to work with heavy equipment under harsh circumstances. To prevent injuries, actions needs to be taken to keep the equipment easy to use. For example, reduce the weight and make sure the lashing equipment can be used while wearing gloves.
2.7 Minimum maintenance
There are approximately 9000 lashing bars on a ship. If one of these lashing bars fail, it can have severe consequences for the cargo. This means that all the lashing bars have to be in good condition and regularly checked. The lashing equipment is a part of the ship, so the only possible time to check the equipment is when the ship is moored at the port. As earlier discussed in chapter 2.5, time in the port costs the ship owner money. This results in little time for maintenance work. So the equipment is part of the ship, but it is used by the employees of the port. This makes it even harder to track mechanical failures.
Possible problems are corrosion, physical damage and the lack of grease. Minimum maintenance is therefor a need for the lashing equipment.
2.8 Cost efficiency
The lashing system is part of the ship, thus an investment is made at the moment the ship is build. Because the lashing system is a safety measure, it adds no direct value. Only the absence or failure of lashing equipment will cost money. Ship owners try to cut the costs where possible and still meet the minimum safety requirements. The system needs to be at the lowest cost possible while fulfilling its task. In chapter 3.5 the different costs are discussed in more detail.
2.9 Power Consumption
To fasten the lashing equipment, a certain amount of power is needed. This power can either be generated by a human person or a power tool. A lower amount of power needed is always better. For human persons, it will prevent injuries and for power tools it will save battery life. In chapter 7 an overview of power sources is given.
3
Specifications
There are certain specifications for a lashing system in order to be compatible with the ship and containers. In this chapter the length of the lashing equipment and connections on both sides are discussed. In the second part, specifications for the lashing system are given based on using the system. The weight of the equipment, installation time and costs are evaluated. All these specifications will give boundary’s for a design.
Geometrical specifications: • Length • Connections Operation specifications: • Weight • Time • Cost
3.1 Length
The length is determined by the distance between the lashing eye on the ship and the corner casting of the container. This length depends on the lashing method (external or internal) and the height of the container. The minimum and maximum length for first and second tier container lashing is calculated [8]. A turnbuckle is universal and can be used for either first or second tier lashing. The length of a turnbuckle can change between 1m and 1,5m [37].
Figure 12: The geometry of a lash in three dimensions [8]
The length of a lash is determined by the geometry of the lash with:
Llash = q
L2
x+ L2y+ L2z (2)
where
Llash = Lash length in [mm]
Lx = Longitudinal part of lash in [mm], the distance between the lashing
connections on the hatch cover and the container stack.
Ly = Transverse part of lash in [mm], the transverse distance from the
connection point on the hatch cover to the corner casting of the container.
Lz = Vertical part of lash in [mm], the vertical distance from the
connec-tion point on the hatch cover to the corner casting of the container.
For the most used 8’6” containers, the length is given in the following table:
Table 1: The length of lashings [29]
3.1.1 Longitudinal distance
This distance depends on the choices of the ship builder. A larger distance will give the lashers more space to install the lashing equipment. But it will increase the angle of the force acting on the lashing plate, see figure 14. A smaller distance will on the other hand take less space and therefor optimize the space utilization on deck. This distance is however always equal or less then 400 mm [8].
Figure 14: Lashing plate with correct and incorrect direction of force [10]
3.1.2 Transverse distance
The transverse distance depends on the lashing method used(internal or external) and the arrangement of the lashing plates on the ship. According to the manual composed by Det Norske Veritas [38], should the lashing angle be between 30 and 60 degrees. A higher or lower angle will reduce the effectiveness of this lash and extra lashings will be necessary.
The lash angle is given by: [8]
βlash = cos−1(Ly/Llash) (3)
3.1.3 Vertical distance
The vertical distance between the lashing plate and the corner casting depends on the height of the container and twistlock. For now, only first and second tier container lashing is considered. The vertical distance is given by: [8]
T op tier1 : Lz = HT L+ HC1− 82 (4)
Bottom tier2 : Lz = 2 ∗ HT L+ HC1+ 54 (5)
where
HT L = Height of Twistlock [mm], the height of a twistlock is between
25mm (manual) and 30mm (automatic) [39].
HC1 = Height of First Tier Container [mm], a standardized container is
between 8’ and 9’6” (between 2438mm and 2926mm) [9].
3.2 Connections
The lashing equipment should be connected between the ship and the container. There is a standardized connection point on both sides, in this chapter the specifications of these points will be discussed.
3.2.1 Ship lashing plate
On the side of the ship, there is a 25mm thick high tensile steel plate with a round eye. This plate is welded on the hatch cover of the ship and has a minimal breaking load of 500kN [5]. This tension force should always be acting in plane with the lashing plate as illustrated in figure 14.
The geometry of the lashing plate is given in figure 15. As can be seen in figure 15, the lashing plate can be installed under an angle. This angle will compensate the longitudinal distance.
Figure 15: Geometry of a lashing plate [11]
3.2.2 Container corner casting
The lashing rod is on the other side connected to either the top or bottom corner casting of a container. The design of the corner casting is standardized in accordance with ISO 1161 [40]. For the design of the lashing equipment, only the side of the corner casting facing the equipment is of interest. The geometry on this side is for the upper fitting given in figure 17 and for the bottom fitting is in figure 18.
Figure 17: Upper Corner Casting [5]
Figure 18: Bottom Corner Casting [5]
3.3 Weight
There is a weight limitation on the equipment because it needs to be handled by human opera-tors. The lashing equipment is stored at the lower walkways, so the employees need to transport the equipment to the desired location [41].
For lifting of equipment the ISO 11228-1 guideline gives a restriction of 23kg under favorable circumstances [42]. This number will decrease when the weight is carried further away from the body or under an angle a graphical presentation is given in figure 19. Also the frequency that the weight is lifted has its influence on the maximum weight, see figure 20.
Figure 19: Weight limit per lifting height [12]
All these variables are combined to calculate the maximum weight for specific circumstances. The NIOSH method prescribes which variables should be taken into account with formula 6 [43].
W eightlimit = LC ∗ HM ∗ V M ∗ DM ∗ AM ∗ F M ∗ CM (6) where LC = Load Constant HM = Horizontal Multiplier V M = Vertical Multiplier DM = Distance Multiplier AM = Asymmetric Multiplier F M = Frequency Multiplier CM = Coupling Multiplier
The current weight of lashing equipment is around 12kg for the turnbuckle and 10kg for a rod going to the bottom of the second tier [5].
3.4 Time
The largest container cranes can handle up to 27 containers per hour at the moment. This number will increase in the coming years due to the technology advancement.
27 Containers per hour today and maybe up to 30 per hour in the near future means that one container need to be lashed in within 2 minutes. Currently a lashing team (4 employees) lashes around 26 to 28 containers per hour [41]. This means that 2 employees need to finish one lash within a minute. This includes picking up the equipment, connecting the equipment, adjusting the length and finally fastening.
3.5 Cost
For a ship owner, the cost of lashing equipment can be divided into three parts.
1. Investment - Equipment needs to be bought from a manufacturer. This price is based on the current steel price en labor costs. Simple and light equipment will result in a lower price. An estimation for the investment costs is around 3-5 Euro/kg.
2. Maintenance - In section 2.7 several reasons for maintenance were given. In order to minimize the costs, the need for maintenance should be reduced. Possibilities for this are an automatic greasing system or the use of high grade materials.
3. Operation - The operational costs depend on the time it takes for lashers to install the container lashings. This determines the number of lashers needed. Lashers cost the port around 50.000 euro per year. With 4 lashers lashing 27 containers per hour this gives a cost of 3.56 euro per container.
4. Container loss - On average 1672 containers [44] are lost each year on sea. Besides the value of the goods inside, millions of dollars are spent each time a container is lost. These millions are spent on the search and recover of the containers. This can be as high as USD 2.5 million per container [44].
4
Forces
In this chapter, all the forces that have an influence on lashing equipment. The following forces are taken into consideration:
• Pretension on the lashing equipment applied by the lasher.
• Allowable forces on ISO containers.
• Forces produced by ship motions on container stacks.
4.1 Pretension
Pretension is the force created by the lasher when installing the lashing equipment. This pretension force should be kept as small as possible in order to keep the lashing elastic [29]. The maximum for a pretension force is 5kN [35], the effect of this rather small force is described by the following formula [29]:
Flash = F0+ ∆F (7)
where
Flash = Total lashing force [kN]
F0 = Pretension force [kN]
∆F = Increase of lashing force due to ship motions [kN]
This equation shows that an increase in pretension force with a constant total lashing force will result in a lower force due to ship motions. The total lashing force is limited by the equipment and the connection points.
4.2 Fatigue
In chapter 1.3.2 the material properties of the lashing equipment were discussed. A high-strength steel (S890) is used resulting in a breaking load of 460kN. The working load however is far below this value with 230kN.
The number of cycles is low due to a small percentage of waves with significant height, see figure 21.
Figure 21: Average wave height. [14]
This combination between low loads and a small number of cycles results in a low chance on fatigue. In literature, no evidence can also be found on failure due to fatigue.
4.3 Allowable forces on the container
Allowable forces on ISO containers is given by the standard ISO 1496-1 [45]. Maximum forces are given in all different directions with their magnitudes. A more clear picture is given by Det Norske Veritas.
Figure 22: The allowable forces on a 20 or 40 foot container. [6]
The circle on the left represents the allowable lashing forces in horizontal and vertical direc-tion. The other forces can be a result of compression due to the weight of other containers or racking caused by ship motions. In the following table the forces are briefly explained. Rack-ing forces are horizontal forces inside the container. Tension forces work outwards from the container and compression forces the other way around.
Now the maximum allowable lashing force can be calculated with the following formula: Flash= min( 225 cos(α), 300 sin(α)) (8) where
Flash = Total lashing force [kN]
α = The angle of the lashing equipment with the deck [degree]
4.4 Ship Motions
The ship motions have a big impact on the force in the container lashings. Ship motions are a result of ocean waves, wind and steering. The most important motion for the force in the lashings is roll, roll is rotation around the longitudinal axis.
Figure 23: The 6 degree’s of freedom of a ship. [15]
There has been done a lot of research on the motions of the ship and their effect on container stacks. Already in 1999 Kohli [10] explained the effect of rolling, pitching, heaving and wind on a container. These forces can be divided in a pressure force on the deck and a sliding force. Kohli was captain of the vessel M.V. Tropical Estoril, for this ship he wrote this manual explaining how to secure the cargo. This manual was made according to Res.A.489, a Recommendation on the Safe Stowage and Securing of Cargo Entities in Ship’s.
After severe container loss from a C11 class post-Panamax container vessel, a research was done on the effect of parametric roll on a container vessel. France [46] finished this research in 2001. Parametric rolling is an unstable phenomenon which causes high rolling angles combined with significant pitching motions. Parametric roll can be caused by a wave period which is half the natural frequency of the ship combined with head seas and a certain wave height. This research proved that the forces generated by parametric rolling where significantly higher than described in the guidelines of that time.
Figure 24: Scale model of a container vessel in extreme head seas at Marin. [16]
Japan has been the leading country in evaluating ship motions and their influence on con-tainer stacks. Already in 1969 Fukuda introduced a statistical prediction model for the response of ship motions. In 2001 Nakamura [17] came with a new model to determine the lashing ar-rangement. This model can in contrast to the ’Fukuda model’ cope with non linearity in the lashing equipment. Nakamura uses an acceleration ellipsoid to calculate the lashing forces. The acceleration that is calculated using the acceleration ellipsoid consists of a static component and a fluctuating component. The static component is illustrated by the offset of the ellipsoid, the fluctuating component is described by the ellipsoid itself. An two-dimensional expression of this ellipsoid is given in fig 25.
Figure 25: A 2D expression of an acceleration ellipsoid for a specific tier in container stack. [17]
Radisic [35] made a manual for the design of lashing equipment in 2004. This manual uses the guideline from Det Norske Veritas as reference for the the calculations on ship motions. But is also discusses the use of empirical and stochastic approaches.
From 2006 till 2009, a joint operation between a number of companies involved in shipping worked on the project Lashing@Sea [47]. This project was under supervision of the dutch company Marin. Numerous researches where started under this project which will be explained in more detail. From 2008 researchers in Japan have worked on models to understand the behavior of container stacks at sea. Kirkayak pioneered in the field of container stack dynamics. The aim was to understand the dynamics of the whole stack in stead of a single container. In 2010 Aguiar [15] published his work on a the scaling of container stacks. The dimensions as well as the forces are scaled using Froude’s law. In the second part of his research, Aquiar explains the modeling and simulation of a single container stack on a shacking table.
Figure 26: Conversion from a 20ft ISO container to a scale model. [15]
Der Germanischer Lloyd creates guidelines for the manufacturing company’s of lashing equipment. In 2011 Wolf [19] made an update for the model used by Der Germanischer Lloyd. This update was based on recent research and new technology like the semi-automatic twist-locks.
Figure 27: A 1:7 scale model of a 7 tier container stack. [15]
In 2013 Aguiar [48] extended his model from 2010. With this model it is now also possible to research the dynamics of stacks with adjacent stacks. Aguiar started with a numerical model that was validated and continued with a quantitative test.
Most of this research was carried out by Japanese researchers, therefor most papers are not available in English. A summary of all the research can be found in the guidelines by Det Norske Veritas and Der Germanischer Lloyd. These guidelines are updated quite regularly when new research become available.
5
Technical demands from the Guidelines
Before 2013 there were 2 major classification companies, Det Norske Veritas(Norway) and Ger-manischer Lloyd(Germany). These two companies merged together in 2013 creating DNV GL. Just before the fusion, both of the companies released a classification for stowage and securing of containers.
5.1 Lashing Force
To determine the force in the lashings, the Germanischer Lloyd [29] created a set of equations to approach this force knowing the ship characteristics. The main inputs for this calculation are the ship’s motions due to waves, wind force and the geometry of the lashing.
The total lashing force in [kN] is calculated with equation 9. The pretension force should be kept as low as possible to allow a larger increase in lashing force.
Z = Z0+ ∆Z (9)
where
Z0 = Pretension force [kN]
∆Z = Increase of lashing force due to ship motions [kN] See eq. 10
Due to forces acting on the container, the container will deform. This deformation also takes place in the lashing because they are connected to the corner castings of the container. This deformation, together with the tension stiffness gives the increase in lashing force.
∆Z = cz∗ ∆l (10)
where
cz = Tension stiffness of lashing element [kN/cm] See eq. 11
∆l = Elongation of lashing element [cm] See eq. 12
The tension stiffness is an extensive property of the lashing equipment. The elasticity modulus is a property of the material of the equipment. With equation 11, this modulus is combined with the geometry of the equipment to find the tension stiffness. The cross-sectional area of a lashing rod is usually around 5.3 cm2.
cz =
Ez∗ A
l (11)
where
Ez = Overall modulus of elasticity of lashing [kN/cm2] See tab. 1
A = Effective cross-section of lashing [cm2]
l = Length of lashing [cm] See tab. 1
5.1.1 Deformation
The elongation of the lashing equipment depends on the deformation of the lashed container as described at equation 10. The lashing angle gives the ratio between these deformations.
∆l = δ ∗ sin α (12)
where
δ = Transverse deflection of lashed container corner [cm] See eq. 13
α = Lashing angle [deg] See table 1
The transverse deflection of the container is given by equation 13. The racking resilience describes the force needed to deflect the container’s frame. The racking force is the force acting on the container. The offset is given by the deflection of containers below the container specified.
δ = cc∗ RFT,1+ v (13)
where
cc = Racking resilience of the container’s transverse frame [cm/kN] See table 3
RFT ,1 = Racking force on top of bottom tier [kN] See eq. 14
v = Transverse offset caused by shifting of bottom container [cm]
Table 3: Standard racking resilience for steel frame containers. [29]
5.1.2 Racking Force
The transverse racking force is calculated according to equation 14. The first part of this equation describes the force acting on the container due to ship motions and wind. The second part takes lashing forces (if present) on top and on the bottom of this container into account.
RFT ,i = RFT,i+1+0.275∗Fq,i+1+0.225∗Fq,i−Ztop,i∗sin αtop,i−Zbottom,i+1∗sin αbottom,i+1 (14)
where
Fq = Transverse force [kN] See eq. 15
Z = Total lashing force [kN]
α = Lashing angle [deg] See table 1
Figure 29: Static full scale tests and finite element analyses on a 20 foot container. [19]
The transverse force is based on the acceleration of the ship, and thus the container, in transverse direction. As well as the wind load on the container. Equation 15 describes the relation between these variables.
Fq= G ∗ bq∗ 9.81 + Fw (15)
G = Container’s gross weight [t] See table 4
bq = Transverse acceleration factor See eq. 16
Fw = Lateral wind load on the container See table 5
Table 4: Minimum and maximum gross weights of containers. [29]
Table 5: The wind and green water load for containers. [29]
The transverse acceleration factor, bq, is a result of the ship movements. The motions having
an effect on this factor are: pitch, heave, yaw, sway and roll. The factor can be calculated using equation 16, but normally the factor is to be determined using the software GL-Stowlash.
bq= (1 + bv) ∗ sin(φ) + bh∗ cos(φ) + 1 9.81 ∗sm2 ∗ 2 ∗ π TRoll 2 ∗ φ ∗ (ZCont− ZRoll) (16) where
bv = Dimensionless acceleration in the global vertical direction due to
pitch and heave
See eq. 17
bh = Dimensionless acceleration in the global horizontal direction due
to yaw and sway
See eq. 17
φ = Ship’s roll angle [deg] See eq. 17
TRoll = Roll period [s]
ZRoll = Height of of roll axis above base [m]
ZCont = Height of container’s center of gravity above base [m]
The accelerations due to ship motions are acting simultaneously. They have to be determined using the extreme values occurring once in 20 years of operations. The relation in equation 17 should hold and bq should attain its maximum value.
bv bv,D !2 + bh bh,D !2 + φ φD 2 = 1 (17) where
5.2 Rules for lashing
Besides the equations to calculate the lashing force in the equipment, the Germanischer Lloyd also prescribes rules for lashing. The first part of these rules is about the placement of the lashings and the second part is about the forces. In this chapter I cite the rules from the Germanischer Lloyd [29].
5.2.1 Placement
The placement of lashings and containers should be done by the following rules. By following these rules, the equations to calculate the lashing forces are legit.
• All the front-ends and all door-ends are stored in the same direction. • Lashing elements should be fitted to the container bottom corner castings.
• Vertical lashings shall be loose to equalize the clearance in the twistlock.
• Internal lashings shall be used. In individual cases, after approval of the GL, external lashings may be used.
5.2.2 Forces
The following rules are set by the Germanischer Lloyd about the forces acting on the lashing equipment. In table 6, requirements are given for lashing equipment.
• Pretension shall be kept as small as possible.
• The centre of gravity is at 45% of the container height.
• For lashing angles between 40deg and 45deg, the maximum permissible lashing force is, in general, 230kN.
• For lashing angles between 40deg and 45deg, the maximum permissible lashing force is, in general, 270kN for lashing to the lower corner casting and 175kN for lashing to the upper corner casting.
• For vertical lashing, the maximum permissible lashing force is, in general, 300kN for lashing to the lower corner casting and 125kN for lashing to the upper corner casting. • If suitable technical proof is given, a lashing force of up to 300kN may be permitted for
other lashing angles.
6
Design Options
In this chapter, possible options for a new type of lashing equipment are discussed. Connections to the ship and container and ship will stay almost the same because these are standardized items. The focus in this chapter will be on the fastening mechanism. The four mechanisms that will be discussed are: Hydraulic, Air, Screw and Lever.
The function of this mechanism is to secure the container with a force of 5kN 4.1. This force has to be produced with a lower input force to make it possible for a human to operate.
6.1 Hydraulic
Hydraulic mechanisms are mechanisms that are powered by hydraulic fluids. These fluids can be any liquid that is in compressible and has a adequate viscosity. But for current systems it is also important that the fluid can lubricate the system. Therefor most fluids are petroleum-based instead of water-based [49].
Figure 30: Hydraulic cylinder [20]
A hydraulic cylinder is able to produce the needed force while the input force is much lower. This is possible by using a pump or lever mechanism. Holding this force for a few months while the ship is on voyage can be a problem. Hydraulic systems have a high risk of internal and external leakage, causing the pressure to drop.
6.1.1 External Leakage
In figure 30 the different parts of a cylinder are drawn schematically. In this figure all the parts can be identified, between all these parts a liquid tight seals need to be installed to keep the pressure from dropping. The seals at ’A’ and ’B’ are static, so no moving parts will cause wear. But the petroleum-based liquid that is leaked at these seals will drop on the deck and make it slippery and unsafe [50].
6.1.2 Internal Leakage
The seals around the piston and the piston rod are subjected to movement. This movement in combination with a high pressure fluid make the seals prone to leakage [50]. Zero-leakage is
6.2 Pneumatic
Pneumatic cylinders work the same as hydraulic cylinders as described in chapter 6.1. The difference is in the material in the cylinder, a gas in pneumatic cylinders and a liquid in hydraulic cylinders. This gas is in most cases air which has some positive and negative properties compared to petroleum-based liquids.
A benefit of the gas air is that when it leaks out of the system it will not harm the environment or stay behind on the deck. Air is also everywhere available, no reservoir is needed.
A downside is that the viscosity of air is almost a thousand times lower than petroleum-based liquid. This will result in a higher tendency towards leakage. According to Parker [51] a leakage of 1 to 3 cubic inches per hour is normal. For long trips (more then a month) a continuous pressure control is needed.
6.3 Screw
Screw tighteners are based on two components with a transmission ratio between them. This transmission ratio means that a displacement of the first part will result in a different displace-ment of the second part. The mechanism should prevent the second component from displacing the first component, this will keep the pressure when no force is applied. Using this principle, the industry developed tightening devices for lashing. The screw mechanisms can be controlled by hand or using a device, depending on the type of equipment.
A downside of a screw mechanism is the need for greasing. There are always metal components moving along each other and grease is needed to prevent wear.
6.3.1 Turnbuckle
Turnbuckles are already the mechanism used in container lashing equipment as explained in chapter 1.3 about the current lashing method. A turnbuckle usually consists of two threaded components screwed in a frame. By turning this frame the threaded components come closer to each other. Turnbuckles can be used between cables, chains and rods.
Figure 31: Turnbuckle with a built in ratchet. [21]
6.3.2 Worm gear
In the shipping of rolling cargo there has been some innovation in the lashing equipment. Besides using the turnbuckle from figure 31, the speedlash system (see figure 32) has been designed.
Figure 32: Speed lashing equipment used to secure rolling cargo. [22]
This piece of equipment consists of a frame that is connected to the deck of the ship. In this frame there is a worm gear with a connection for a spinning tool at the top. On this worm gear, there is a second hook that will travel along the frame when the worm gear is turned. The current equipment has a minimum breaking load of 200kN and a safe working load of 100kN. A worm gear has property’s that are useful for lashing. First, the high gear ratio that can be achieved. Second, the worm gear can displace the hook, but the hook is not able to turn the worm gear.
6.4 Lever
A lever makes it possible to transform a small force with a large displacement in a higher force with smaller displacement. This system is currently used in all fields of cargo securing.
6.5 Cable
Cables are widely used in lifting and pulling operations. High loads can be lifted using winches and sheaves. The cable is wound around the winch, by turning this winch the cable is tightened. For the cable thickness, table 7 can be used as an approximation.
Table 7: Minimum breaking strength and safe load for Bright wire, uncoated, fiber core wire rope, improved plow steel. [30]
If the cable is getting thicker, bending the cable will become harder. A minimum diameter of bending should be considered. In figure 34 a rule of thumb for this diameter of bending is given.
Figure 34: Rule of thumb to calculate minimum diameter of bending. [24]
7
Power Sources
There are various sources of power that can be used to power the equipment and tighten it. For the lashing equipment currently used in the industry, human power is used to tighten it. First the torque needed is calculated, in the second part of this chapter power sources are described.
7.1 Torque required
A sufficient amount of torque is needed to turn the turnbuckle. There are two places where there is friction that determines the amount of torque needed. First there is the thread of the screw which tightens the lashing. Second is the connection between the turnbuckle and the rod, this is steel sliding over steel. The friction in this part is:
Figure 35: Required torque needed on the screw side. [25]
The second part is where the turnbuckle is connected to the rod. The friction torque here is calculated with formula 18.
Tw = Fn∗ µ ∗ d (18)
where
Tw = Friction torque [Nm]
Fn = Lashing force [N] 5000N
µ = Coefficient of friction 0.8
d = Distance between center and force [m] 0.05m
The combined torque needed to tighten the lash is now 80Nm + 200Nm = 280Nm . Loos-ening the lash can be much more difficult if more tension has been build up during the voyage.
7.2 Battery Impact Wrench
A battery driven impact wrench is mobile compared to pneumatic or wired devices. The torque produced is lower then the alternatives but still sufficient with around 500Nm. The ”Metabo SSW 18 LTX 600” is the most powerfull impact wrench at the moment.
Figure 36: Metabo SSW 18 LTX 600 battery impact wrench. [26]
Table 8: Properties of the Metabo SSW 18 LTX 600. [26]
7.3 Pneumatic Torque Wrench
Pneumatic torque wrenches are similar to battery impact wrenches in the way power is trans-ferred to the equipment. If pneumatic air is available on the ship pneumatic tools could be a good alternative because no battery’s need to be replaced.
The ”PneuTorque PTM-72” can be fitted with different gearboxes to reach torque outputs of 2000Nm.
Figure 37: PneuTorque PTM-72 pneumatic torque wrench. [52]
7.4 Torque Wrench
A turnbuckle is always operated by hand, a lever is used to rotate the frame. For smaller turnbuckles there are devices to rotate the frame. These devices are automated pneumatic wrenches with an open end as shown in figure 38. [27]
Figure 38: Pneumatic wrench with an open end. [27]
Larger versions of these automatic open end wrenches have also been created by the company Speed Sincher. The Speed Sincher device is able to tension large turnbuckles to a tension of 45kN. [28]. This piece of equipment, as can be seen in figure 39, is gas powered.
Figure 39: The speed sincher, able to tighten turnbuckles on deck. [28]
7.5 Human Power
Currently, for all container lashings, human power is used to tighten the lashes. The power a human may produce is limited by physical limitations and the ISO 11228-1 guideline as described in chapter 3.3. Under favorable circumstances, a maximum load of 25kg may be produced. To maximize the torque produced with this load, lashers use all kinds of bars of approximately 0.5m. This results in a maximum torque of 125Nm.
8
Conclusion
In this report an overview of lashing methods and possibilities for improvement was given. This conclusion will be in two parts, the first part will give a conclusion about the overview of the lashing method. In the second part a conclusion for future designs will be given.
Overview - Since the beginning of ISO container shipping in 1955, lashing was needed. A lashing method was introduced that has similarities with lashing on trucks and airplanes. A cable or rod is brought under tension using a turnbuckle. Unless research in the behavior of container stacks and ships and numerous accidents involving container lashing. There has been no innovation in the lashing method. This is probably because the lashing system is owned by the ship owner. But the people who install the lashings are employed by the port.
New method - For a new lashing method, the arrangement of the equipment will be kept the same. So the length and connection points will be similar to the current method. A new lashing method is subjected to the following technical demands and criteria: Technical demands:
• Compatible with current lashing methods and arrangements
• Compatible with all container types and sizes • A minimum breaking force of 460kN
• Usual working load 230kN
• A weight of less then 12kg
• The length is adaptable from 1.5m to 1m
Criteria, the new concepts should: • Be reliable
• Have a non complex design
• Have a Quick and easy installation method
• Consist of lightweight components • Have easy maintenance
• Be cost efficient
There are four mechanisms that can be used to secure the containers. From the mechanisms it is most likely that it will be one of the mechanical mechanisms. This because pneumatic and hydraulic systems have more components that wear out causing the fluid or gas to leak.
Guidelines - For the design of lashing equipment guidelines and standards give boundary conditions for the technical specifications. The following guidelines and standards need to be used:
• Germanischer Lloyd - Stowage and Lashing of Containers • Det Norske Veritas - Container Securing
• American Bureau of Shipping - Guide for Certification of Container Securing Systems
• ISO 1161 - Container corner and intermediate fittings
• ISO 11228-1 - Ergonomics. Manual handling. Lifting and carrying • ISO 1496-1 - Containers specification and testing
9
Recommendations
In the further process of designing a new type of lashing equipment for container lashing on vessels, the following points should be considered.
• Several design options should be made taking the mechanisms from chapter 6 into account. It is possible that there are more mechanisms which are not discussed in this report. More mechanisms are possible and should be taken into account.
• These design options can then be judged with the design criteria from chapter 2.
• The loads from table 6 are the loads to which the new equipment should be designed.
• No research has jet be done in the use of other materials, this should be analyzed while making the design options.
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Appendix A
^ P S A ANTWERP
PSA Innovation challenge
Project name:
Innovative Lashing Equipment By: Edwin Van Inghelghem, Terminal Manager Deurganck Terminal PSA Antwerp
Jurgen De Wachter, Terminal Manager Europa Terminal PSA Antwerp Raf De Ruysscher, Safety Manager PSA Antwerp Joeri Stefanoff, Operational Controller PSA Antwerp
^ P S A ANTWERP
Innovation Challenge
Introduction.
Since the introduction of the Emma Maersl< in 2006 the race for even bigger ships hasn't stopped. Shipping lines are taken ULCV into service at a fast pace to reduce their costs per slot as their ULCVs can transport more TEU simultaneously and have engines designed to reduce bunker consumption significantly.
For Shipping Lines active on the Northern Europe - Far East it's inevitable to invest in Mega Vessels to be able to compete and reduce the operating costs. In order to reduce these costs they must have a fast Turnaround Time inside the port. Bunkers savings can only be made at sea and as much cargo as possible needs to be transported between ports in the shortest time frame possible.
In order to do so, Shipping Lines are putting more pressure on terminal operators expecting a higher vessel rate compared to a few years ago. Productivity on terminals needs to
increase regardless of all consequences for the terminal. Terminals are obligated to invest in Mega Vessel Handling Facilities just t o maintain current volume flows.
Not only equipment and facilities are put to the test but also dockers suffer from the extra pressure and especially the lashers ^. In order to reduce the port stay more Quay Cranes (QC) are put on the vessel simultaneously to boost the boxes handled per hour (vessel rate). This means that in the beginning o f t h e operations more bays need to be unlashed at the same time to let the QCs start on time. At the end of the port stay cycle more QCs will be jointly finishing the vessel resulting in the fact that the lashers will need to lash the vessel in a shorter time frame.
Contradictory to the innovative ULCV design the lashing gear and methods on board haven't changed in the last 20 years. Lashers are still working in the exact same conditions with the exact same material as decades ago. It's still an intensive manual process in a dangerous environment. Lashers need to handle heavy lashing rods and need to loosen or tighten turnbuckles which are suffering from the weather conditions at sea. The lashers work close to each other in very narrow spaces with not much room to maneuver. As a consequence lashers are sensitive to accidents especially i f t h e lashing equipment is not well maintained b y t h e Ship's Crew.
As a terminal operator we get the impression that Vessel Operators and Shipyards do not see the need of introducing new lashing methods as the current system still works for them. The current system is easy t o implement for the Shipyard and is easy t o maintain by the Ship's crew.
' At PSA Antwerp lashers are not part of the QC gangs, they are ordered based on the number of lashing bars to be performed. They do not handle twistlocks.
^ P S A ANTWERP
, Innovation Challenge
At sea the Ship's crew will first of all control the state o f t h e turnbuckles. If there's slack on the turnbuckle - lashing rod combination, the turnbuckle will be tightened slightly.
Manipulation is reduced to a minimum and is not as intensive as in the port. Second of all the crew should grease the turnbuckles at sea so that they can be manipulated easily, unfortunately this is not always the case. Sometimes they are not greased at all or greased with the wrong substance making it very hard to turn them.
HSSE.
Between 2005 and 2013 ... lashing labour accidents with at least one day of absence occurred at PSAA. Almost 40% of these accidents are related to the manipulation of turnbuckles as shown in the below pie chart.
To manipulate the turnbuckles lashers are quiet inventive and bring their own material to the job. They use light weighted steel bars or monkey wrenches to avoid carrying around heavy tools. Regardless of their own efforts to facilitate the work, turnbuckles can be very hard to manipulate. At sea the lashing material is subject to the movements of the ship. When the ship is rolling and pitching the lashing material is stretched and compressed constantly. This makes it very hard for the lashers to loosen the turnbuckles when the ship arrives at the port.
On top of the use of their own tools, they have to put their body weight into the movement which makes them very vulnerable for accidents. If they push too hard and the turnbuckle loosens suddenly they risk smashing their arms and fingers on the lashing material or the ships structure. If they pull too hard they can even fall or trip on the lashing bridge. In both cases it can quickly become a very dangerous situation. Constant pushing and pulling movements also can cause aching muscles in arms and shoulders. It's very rare to find people who have done this job for their entire professional career.
