Erhalten Sie Zugang zu diesem und mehr als 300000 Büchern ab EUR 5,99 monatlich.
- Herausgeber: Books on Demand
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
A Guide for Loading, Handling, Stowage, Securing, and Transportation of Different Types of Cargoes, Except Liquid Cargoes and Gas. The most common cargoes and their stowage and calculation are described - Container Cargoes, Reefer Cargoes, Bulk Cargoes including Grain and Grain products, Heavy Lift Cargoes, Timber Cargoes, Steel Cargoes and Ro-Ro Cargoes. For each cargo the stowage and loading principles are described as well as the securing of these cargoes which includes all necessary calculations.
Sie lesen das E-Book in den Legimi-Apps auf:
Seitenzahl: 419
Veröffentlichungsjahr: 2015
Das E-Book (TTS) können Sie hören im Abo „Legimi Premium” in Legimi-Apps auf:
Ähnliche
Content
1.1 What is Cargo?
1.2 What Kind of Cargoes do we know?
1.3 The Parameter to Carry Cargo Successfully
1.3.1 The Planning
1.3.2 Stowage and Cargo Hold Space
1.3.3 The Distribution of the Cargo
2. The Different Cargoes
2.1 The Containerized Cargo
2.2 The Different Container Parts
2.3 Preparation of the Container and Stowing of the Cargo Inside of the Container
2.4 Identification of Containers
2.4.1 Marking and Numbering of Containers
2.4.2 Bays, Rows and Tiers
3.0 Lashing Material and Lashing Arrangement for Containerized Cargoes
3.1 Stress Acting on the Container
3.1.1 Changes of the Physical Parameter due to Different Weight Distributions in the Tier when the Vessel Rolls
3.2 The Lashing Material
3.2.1 Handling and Safety Instructions for Loose Lashing Material
3.2.2 Cargo – Container Securing Plan
3.2.3 Stowage and Securing Principle
3.2.4 Consequences in Alteration of any of the Permissible Values
3.2.5 Cases Which Have to be Avoided when Stowing Container
3.2.6 Types of Container Damages and Lashing Failures
4.0 The Reefer Container
4.1 The Integral Refrigeration Unit:
4.2 The Insulated Refrigeration Unit
4.3 The Redundant System
4.4 General Aspects When Loading Reefer Container
5.0 Reefer Cargo
5.1 General Information
5.2 The General Division of Reefer Cargo
5.2.1 Carriage of Mixed Products
5.3 Preparation for Taking Over Reefer Cargo
5.4 Precooling and Ice Test
5.5 Reefer Cooling Technology
5.5.1 General Requirements by Classification Societies
5.5.2 The Entropy–Temperature Diagram in Regards to the Cooling Process
5.5.3 The Explanation of the Entropy Diagram
5.5.4 The Coefficient of Performance (COP) for Reefer processes
5.5.5 Refrigerants and Numbering of Refrigerants
5.5.6 The Different Cooling Systems Used on Board
5.6 Planning and Stowage of Reefer Cargo
5.6.1 Air Flow in the Hatches
5.6.2 Stowage Arrangement
5.6.3 Cargo Distribution
5.6.4 Stowage Plan for Reefer Cargoes
5.6.5 Reefer Cargo Damages and Causes
5.6.6 Maintenance During the Voyage
6.0 Bulk Cargo
6.1 Categories of Bulk Carrier
6.1.2 Types of Bulk Carrier
6.2 Design and Construction of a Bulk Carrier
6.2.1 Stability Related Problems on Bulk Carrier
6.3 Cargo Distribution and Loading Procedures
6.3.1 Homogenous Loading Condition (Fully Loaded Ship)
6.3.2 Alternative Loading Condition (Fully Loaded Ship)
6.3.3 Block Loading and Part Loading Condition
6.4 Preparation for Loading Bulk Cargoes
6.4.1 Preparation of the Hatches
6.4.2 Properties of the Cargo to be Loaded
6.4.3 The Angle of Repose
6.4.3.1 Factors Affecting the Shear Strength that Determines the Angle of Repose
6.4.3.2 Influence of the Angle of Repose to Ships’ Stability
6.5 Loading and Discharging Procedure for Bulk Cargoes
6.5.1 Ratio Between Loading Rate and De-Ballast Rate
6.5.2 The Loading Procedure
6.5.3 Loading Algorithm for Loading Low and High Density Cargo in Bulk
6.5.4 Onboard Loading Guidance
6.5.4.1 Trimming Procedures
6.5.5 Calculation of the Amount of Cargo Loaded
6.5.5.1 The Constant
–
A Variable in the Draft Calculation
6.5.5.2 Second Trim Correction (Nemoto’s Correction)
6.5.5.3 Cumulative Errors which can Occur During the Draft Survey
6.5.6 Discharging Plan and Discharging of Bulk Cargo
6.5.7 Liquefaction of Bulk Cargo
6.5.7.1 Flow Moisture Point, Transportable Moisture Limit
6.5.8 Responsibilities of the Shipper
6.5.9 Responsibilities of the Master
6.6 Grain and Grain Products
6.6.1 The Grain Code and the Intact Stability Requirements
6.6.2.1 Stability Regulations and Requirements when Loading Grain Products
6.6.2.2 Voids in Spaces Loaded with Grain
6.6.2.3 The Loss of GZ if Grain Cargo Shifts
6.6.2.4 Compensation for the Vertical Component of Shift of Grain
6.6.2.5 Calculation of Actual Grain Heeling Moments and Approximate List if Grain Shifts
6.6.2.6 Calculation of the residual area
7.0 General Cargo
7.1 Measurement of the Volume in the Hatches
7.2 Preparation for Taking Over General cargo
7.3.1 Cargo Planning and Stowage Plan
7.3.1.1 The Stowage Plan
7.3.2 Loading, Discharging and Maintenance During the Voyage
7.3.2.1 Maintenance During the Voyage
7.3.2.2 Securing of the Cargo
7.4 Cargo Claims Regarding General Cargo
8.0 Heavy Lift Cargo
8.1 The Different Types of Heavy Lift Ships and Their Characteristics
8.1.1 The Project Cargo Ship
8.1.3 Dock Ship
8.1.4 Semi-Submersible Ships
8.1.5 Semi-Submersible Heavy Lift Ships and the Influence of Wheeling
8.2 Cranes and Hoisting Devices on Heavy Lift Ships
8.2.1 The Conventional Type of Crane
8.2.2 The Conventional Type with a Runner (Cable)
8.2.3 The Conventional Type – Topping with Hydraulic Cylinders
8.2.4 The Low Type Crane
8.2.5 The Mast Crane
8.3 Force Acting on Cranes and Derricks
8.3.1 Height of the Cargo Hook Against the Deck
8.3.2 The Hoisting Gear
8.3.3 Forces Acting on the Lifting Gear, Lifting an Asymmetric Cargo
8.3.4 Calculation and Determination of Sling Length
8.3.5 Lifting of Overheight Cargoes – Stability of Suspension Arrangements
9.0 Loading of Heavy Lift in Single Crane and Tandem Crane Operation Lifting Symmetric and Asymmetric Cargoes
9.1 Single Crane Operation
9.2 Tandem Operation Without Traverse
9.2.1 Calculation of the Lifting Points when Only the COG of the Cargo is Known
9.3 Lifting of Cargo by Means of a Spreader, Beam or Traverse
9.4 Considerations when Lifting a Cargo by Means of Cranes
9.5 Loading Procedure for Loading Heavy Lift Cargo Using Ship Cranes
9.5.1 Loading / Discharging of Heavy Lifts with Ship Cranes
9.5.2 Procedure for Loading a Heavy Lift with two Cranes
9.5.3 Procedure Guide for Discharging
9.6 Bedding and Securing of Heavy Lift Cargo
9.6.1 Calculation of the Bedding
9.7 Securing of Heavy Lift Cargo
9.7.1 Securing of Cargo – Basic Physical Principle
9.7.2 Mechanical, Dynamical, and Static Stress on the Cargo
9.7.3 Forces Acting on the Cargo
9.7.4 The Stowage Position of the Cargo
9.7.5 Friction
9.7.6 Securing Equipment
9.7.7 The Different Lashing Materials
9.7.7.1 Wire Ropes as Lashing Material
9.7.7.2 Chains as Lashing Material
9.7.7.3 Webbings as Lashing Material
9.7.7.4 Turnbuckles and Shackles and D-Rings as Lashing Material
9.7.8 Sea Fastening to Secure the Cargo
9.7.9 Main Points to be Determined when Lashing Heavy Lift Cargo
9.7.10 Calculation of Polar Radius of Inertia for large dimensioned cargoes
9.7.11 Meteorological Voyage Planning for a Heavy Lift Ship
10. Timber Cargo
10.1 General Aspects of Timber Cargo
10.1.1 Timber Load Line Marks
10.2 Cargo Planning
10.3 Preparation for Taking Over the Cargo
10.4 Why Timber or Lumber or Logs as Cargo are so Dangerous
10.5 Loading and Calculation of the Cargo to be Carried
10.6 Calculation of GM and KG
10.7 Transportation of Logs
10.7.1 Calculation of Hog wire and bending moments acting on fixed and portable stanchion
10.7.2 Bending moment in uprights for Log cargoes
10.8 Securing of Timber Cargo
11.0 Steel Cargo
11.1 Handling of Steel Cargo
11.1.1 Steel Coils
11.1.2 Hot and Cold Rolled Steel Sheets
11.1.3 Steel Plates
11.1.4 Pipes
11.1.5 Wire Rods
11.2 Planning
11.3 The Golden Rules of Stowage
the following five Golden Rules should always be observed.
11.4 Strength of Tank Tops
11.5 The Calculation of Steel Cargo – Maximum Cargo Which can be Loaded
11.6 Damages to Steel Cargo Products
11.7 Ventilation of Steel Cargoes
11.7.1 The Influence of Thermal Conductivity When Transporting Steel
11.8 Carriage of Steel Cargo – Regulatory Framework
11.8.1 Bill of Lading
11.8.2 Steel Cargo Condition Clauses
12.0 General Introduction of Roll-on/Roll-Off Cargo and Ships
12.1 Construction of the Vessels
12.2 Cargo Planning on Ro-Ro-Ships
12.3 Loading of the Cargo and Securing of the Cargo
12.4 Variation of Ro-Ro Ships
1.1 What is Cargo?
Answering the question will be difficult because cargo is only a name for different kinds of products which will be transported from one point of the earth to another. This can be done by car, aircraft, truck, or ship. The most useful kind of transportation and also the most efficient kind of transportation is the ship.
A ship can carry, compared to a truck or railway, much more different products and also more masses. These goods will be transported generally for commercial gain.
1.2 What Kind of Cargoes do we know?
In general we know:
Liquid cargoes
Dry cargo in bulk
Heavy Lift/Project cargo
Reefer cargo
General Cargo
There are also some special cargoes which are partly belonging to the kinds of cargoes mentioned above, like dangerous goods which can be either dry cargo, refrigerated cargo or liquid cargo.
Each of the above mentioned kind of cargoes has special parameters to be known. Without knowing these parameters, a transportation of cargo is not possible. The different cargoes will be discussed in chapter 2, but for all cargoes to be loaded, general guidelines can be worked out. These guidelines should be followed prior loading, during loading, prior and during discharging and also during the voyage.
1.3 The Parameter to Carry Cargo Successfully
1.3.1 The Planning
The planning for loading and discharging of cargo is a compact unit. First of all we have to calculate the cargo, which means how much cargo can be loaded. The planning for the cargo operation is based on the cargo to be loaded. The quantity of the cargo to be loaded will be given by the charterer. The Master and/or Cargo Officer (normally the Chief Officer) have to check and clarify if the ship can load the said amount of cargo.
The next step – and for most of the vessels the first step – is where is the cargo bound for – what is the discharging port(s). For the calculation of the planned voyage the master not only needs to know how much cargo can be loaded, further he also must know:
Properties of the cargo to be loaded
Distance between port of loading and port of discharging
Climatic changes during the voyage which might influence the cargo
The Energy Efficiency Operation Index (EEOI) given by the company and how he can achieve the EEOI
The fuel oil consumption and average speed in accordance to the EEOI
The weather condition expected for this voyage – meteorological voyage planning and voyage/passage planning
The expected stability/trim condition during the voyage
The ballast water management regulations valid for this voyage and how it can be achieved in regards to the stability condition of the vessel, if ballast water management must be done (voyage plan)
Tidal condition on port of loading and port of discharging
Draft limitations in the port of loading and port of discharging
At what hatches will be loaded or discharged at the same time (important for the distribution of the cargo)
Comply with the international load line regulation
Comply with the terms given in the charter party
There are for sure many more aspects the ship command must take into account, but these are the most important ones.
The distance between the POL and POD1 will be needed to calculate the required amount of fuel oil which will be consumed during the voyage. The HFO and MDO consumption has a direct influence on the load line regulation and the stability/trim of the vessel and as well for the distribution of the cargo. The consumption of fuel oil is one of the most important parameters to know prior loading especially when loading cargo in bulk.
The simple formula for the calculation of the consumption is:
There is still one factor missing in the consumption calculation. The factor missing is the safety margin for weather influences (bad weather on the voyage which causes the ship command to deviate from the origin voyage plan). This will result in more consumption of fuel oil which must be taken into account. The safety margin can be obtained by 15% to 25% more bunkers to be on board.
For example:
The safety margin will differ due to the different bunker capacities of the ships and the daily consumption rate.
Another parameter for the pre-calculation of the cargo is the deadweight and displacement of the vessel. The detailed calculation is part of “Stability &Trim”. But the draft of the vessel is important for the planning of the voyage because the ship command must comply with the load line zones the vessel will trade in. Furthermore, the required maximum drafts in the POL and POD – given in the draft limitations – are part of the displacement calculation.
1.3.2 Stowage and Cargo Hold Space
After knowing how much cargo must be loaded (charterer’s figures) the ship command must calculate if the cargo can be loaded on board of the vessel.
Each cargo requires a different kind of stowage (see also Chapter 2 – “The different types of cargo”). For this reason the ship command must check prior loading if all necessary stowage material and lash material is available on board to guarantee a good stowage and loading/discharging procedure. All checks should and must be done prior loading. The ship command has to declare that the vessel is ready for loading (N.O.R)2.
For the stowage of the cargo, the Stowage Factor (S.F.) of the cargo must be known. The stowage factor is a mathematical figure which expresses how much space will be occupied by the cargo if the said cargo will have certain measurements (H*L*W)3. This will be expressed in the S.F. It is the Volume occupied by the unit weight of cargo expressed in cubic meter or cubic feet.
The stowage factor will normally be given by the charterer, but it can also be calculated.
Formula for S.F.:
For example:
For most of the cargoes to be loaded, the stowage factor is already known or given by the charterer in advance. It is necessary for the ship command to have the S.F. in advance to prepare a preloading plan. The measurement of the hatches and the theoretically cargo to be loaded can be found in the vessel’s capacity plan.
The stowage of the cargo differs also with the cargo to be loaded and how exact the stevedores will work as well as how exact loading and stowage of the cargo will be supervised by the Officer of the Watch.
Another important factor in respect to the stowage of the cargo is the broken stowage. The broken stowage can be also calculated.
Broken stowage is defined as the amount of space on a ship that is lost during stowage, measured in percentage of total bale space5. The percentage of space lost varies depending on the type of cargo, container shapes, and the bays used.
Therefore:
The broken stowage is then the space between the packages which remains unfilled due to bad stowage expressed in percentage.
Example:
In this example, the broken stowage for this hatch will be 16,7%.
The broken stowage is a result of packing material which was used, or the ship’s design in the holds (remember: not all areas can be used for the stowage of cargo but are part of the area calculation in the hatches). Often times the case is: Just a result of bad stowage done by the stevedores.
Is the loss of stowage higher than agreed in the charter party, the master has to protest against the loss of stowage using the letter of protest to protect the vessel and the ship owner against any claim done by the charterer.
1.3.3 The Distribution of the Cargo
First: The distribution of the cargo is normally part of the ship command. It depends on the kind of cargo to be loaded and the type of vessel (Compare Bulk Carrier with a container ship or General Cargo vessel). On a container ship, the stowage plan is already prepared by the cargo planner ashore and therefore also the distribution of the cargo. Here the ship command only has to check that the distribution (weight distribution) is in accordance to the limitation of the ship’s longitudinal strength and stability and trim criteria.
Illustration 1: Normal Longitudinal Strength Curve of Feeder Container Vessel
The cargo distribution has to be done in accordance to the longitudinal strength condition and limits of the vessel. In order to obtain this requirement, the vessel will be loaded and discharged in sequences which have to be strictly followed. If the shear and bending stresses are above the limits, the cargo must be distributed so that these limits will not be overdue. This can be achieved by ballasting or de-ballasting, but sometimes this is also not possible anymore – then the distribution must be changed.
Second: The port criteria have to be observed and checked.
Maximum required draft and trim for loading and discharging
Tidal situation in port (high and low water times and heights)
Height of the berth etc.
These are influences on the cargo distribution.
Third: Kind of cargo to be loaded: For example, Iron Ore: Iron Ore cannot be loaded in all hatches. The loading procedure, certified by the classification society, must be strictly followed.
Logs and sawn timber, for example, have to be distributed in accordance to the relation hatch to deck, so as not to suffer any stability problems.
Fourth: Trim and draft – The cargo has to be distributed so that the trim and draft will not affect the maneuverability of the vessel or the load line convention.
Whenever trim, stability, or longitudinal strength is not in accordance with the given figures in the stability booklet (approved by the classification society), the distribution of the cargo must be changed in order to fulfill the requirements given by the classification society. The changes must be discussed with the charterer or his representative.
Fifth: The distribution should also be in accordance with the lashing arrangements (for example: Log and timber cargo in accordance with the International Timber Code, or Bulk Cargo with the BLU-Code).
Sixth: Distribution should be done in accordance with other cargoes to be loaded (separation of cargo. See Dangerous goods – IMDG Code). Other cargoes are reacting to the odor of the cargo stowed nearby.
Seventh: Distribution in accordance with loading and discharging facilities (Grain, Coal in Bulk, Heavy Lift, Reefer cargo).
Eight: Distribution in accordance with other loading and discharging ports – Port sequence must be observed and taken into account.
The above presented eight rules for stowage and distribution are showing us that the start of a successful transportation of cargo is depending on the preplanning that is done.
3 Height x Length x Width of the cargo to be loaded
4 Liquid cargoes, like oil products, are gassing which cost an increase of their volume
5 The cargo capacity of a vessel below deck, measured in cubic meters or cubic feet.
2. The Different Cargoes
2.1 The Containerized Cargo
Over the past 30 years, the container has been the most common cargo transportation unit on board of merchant vessels. Nearly all kinds of cargo can be transported with and in a container, from Reefer Goods to Heavy Lift, Bulk cargo, Liquid cargo and General cargo. To transport these kinds of cargoes, different types of containers have to be designed. In general, a container is a small hold and has to be treated as if it would be a cargo hold.
We know different types of containers:
20’ Dray Container
20’ Reefer Container
20’ Flat Rag Container
20’ Tank Container (including Container for Gasses)
40’ Dry Container
40’ Reefer Container
40’ Flat Rag Container
40’ Tank and Gas Container
45’ Dry Container
48’ Dry Container
49’ Dry Container
53’ Dry Container
20’ and 40’ fully ventilated Container
20’ and 40’ high Cube Container
The 48’& 49’ and especially the 53’ containers are often times used for transportation to the USA. Especially for these types of containers the ship must be designed for. The mate on board must have knowledge about the different types of containers, where they can be stowed, and the different parts of the containers. The last-named is very important for damage reports.
The container is a weak box loaded with heavy cargo inside and above. The mass of the cargo is accelerated by the six types of movement of a ship in response to sea conditions and by additional forces from wind and green seas. To handle these forces and to secure the valuable cargo, containers need to be further stabilized and secured by lashing equipment.
Illustration 2: Six Movements of a Ship
The stresses acting on the containers are in vertical, horizontal, and transversal direction.
2.2 The Different Container Parts
Illustration 3: The Different Construction Parts of a Container
Illustration 4: Bottom Construction
The above presented parts are the same for all containers. Some containers have additional parts like integrated reefer units etc.
2.3 Preparation of the Container and Stowing of the Cargo Inside of the Container
If the container is loaded to its maximum capacity, the weight of the cargo must be distributed as evenly as possible over the floor area. The load-carrying components of the container floor structure are the bottom side rails which absorb the load of a cargo via the container floor. For safe transport it is important for as many of the bottom rails as possible to be loaded. Point loads are to be avoided, since they can damage the container floor. Point loads always occur when relatively high weights are concentrated on a small bearing area.
If planning the cargo stow inside the container, also the maximum line load is of importance. For 20’ and 40’ container it states a maximum line load of 4.5 metric tons/m for a 20' container and 3.0 metric tons/m for a 40' container.
Example 1: A cargo weighing 14 t extends over a length of 5,3m. This gives a line load of
The result shows that this cargo could be transported in either a 20' or a 40' container as 2,64mt<4,5mt for a 20’ container and 2,64<3,0mt for a 40’ container. The limits of the line load will be not exceeded.
Example 2: A cargo weighing 18t extends over a length of 5,3m. This gives a line load of
This cargo could only be transported in a 20' container. In a 40' container the maximum line load would be exceeded and transport would therefore be disallowed.
However, the cargo can be also packed in a 40' container. Therefore, the bearing area must be enlarged to ensure safe transport. This may be achieved, for example, by laying dunnage or a "sled" under the cargo. Where dunnage is used, it must be ensured that the lower wooden planks lie lengthwise and are thus supported by several container bottom cross members. If using sleds, the skids of a "sled" must also lie in the lengthwise direction of the container.
The cargo loaded in a container will be mostly on pallets. This allows a fast loading and discharging of the cargo inside the container. Reefer cargo will be also single stowed, i.e. package by package.
Before the container will be loaded, the container has to be cleaned from inside, all old residues have to be out, the container must be free of any odor and there has to be an inspection after the cleaning by the company who is responsible for the stowage of the container. A lot of container damage claims are based on the fact that the cargo was affected by bad odor resulting from previous cargo. If the container is free of any odor, the container can be loaded. It is now up to the shipper to distribute the cargo in the container. Here it is usually practice that a stowage plan is prepared, as well as a lashing plan how the cargo will be secured inside the container. Sensitive cargo should be further protected against sweat water and humidity which can destroy the cargo. If, for example, the humidity of loaded coffee is exceeding 13%, a fully ventilated container must be used.
Illustration 5: Fully Ventilated Container
It should be assured that the inspection of the container and the cargo to be shipped in the container must be carried out by the shipper or the company who are packing the container on behalf of the shipper. An inspection certificate should be issued to state that the container was dry.
This inspection cannot be rechecked by the ship command; when the container will be loaded, the container is already sealed and cannot be opened anymore by the officers. Only if there are differences between the loading papers and the actual cargo inside the container, the master can make a protest and the shipper must now proof that all the information is in accordance to the cargo loaded. If not, the container should not be accepted by the master.
Another problem for the ship command is the securing of the cargo inside of the container. Cargo stowed in containers must be secured on all sides to prevent shifting, in particular towards the door. Spaces between packages and/or container walls must be filled. Secure the cargo by using the lashing points provided on the top and bottom side rails and on the corner posts. Containers should be packed and the cargo secured in accordance with guidelines for packing cargoes other than bulk cargo in or on cargo transport units (CTUs) for carriage by any means of transport at sea and ashore.
The CTU packing guidelines published by the International Maritime Organization (IMO) and International Labor Organization (ILO) from 02-05-1997 supersede any previous applicable container packing guidelines.
2.4 Identification of Containers
2.4.1 Marking and Numbering of Containers
The container is a standardized cargo, meaning the measurements for the different container types are already fixed. These are standard measurements. The normal standard 20’ and 40’Container measures are:
The container will be identified by its identification Number according to the ISO6346.
Illustration 6: Identification acc. ISO 6346
Illustration 7: Size and Type Code – 6346
Illustration 8: Volumes and Weights Marking
2.4.2 Bays, Rows and Tiers
The container will be stowed according to an international system of numbering the location of the container. To locate a container on board and also to make a correct stowage plan (Bay Plan), the system is divided in bays, rows and tiers – on deck and in the hatches. This numbering is an international standard.
Bays: Each container loaded is split into compartments which will be termed as bay. The bays are depending on the size of the vessel. For example: It will proceed from 01 to 60. Bay 01 is the first bay forward of the ship and Bay 60 is the last one, near the stern of the ship. Odd numbered bays are 1,3,5,7 etc. and are for 20’ container stows, and even numbered bays, 2,4,6,8 etc., are for 40’ container stows. Between two 20’ bays there is a 40’ bay. There are exemptions because on some ships where no 40’ container can be stowed we will have special 20’ container bays. The same holds for 40’ container bays.
Rows: The position where the container is placed across the width of the vessel. The odd numbers are on the right side and the even numbers are on the left side.
Illustration 9: Bays, Rows, and Tiers on Deck6
If the ship can load 10 containers from side to side, the number of rows is an even number, then no zero row will be used. If the ship can, for example, load 11 container from side to side, then a center row, the zero row, will be used. Illustration No.9 is presenting an amount of odd numbered rows. Here the zero row will be used.
Illustration 10: Rows Including Center Row7
Tiers: The tiers are marking the level where the container is loaded. The tier numbers on deck are always starting with 8, followed by even numbers, and in the hatch they start with a 0, followed by even numbers. Example Deck: 80,82,84,86,88,90,92 etc. In the hatch: 02,04,06,08,10,12, etc.
see Illustration No.11 for a better understanding:
Illustration 11: Bayplan with Bay, Rows and Tiers8
The distribution must be exactly in accordance to the bay plan (Illustration No.11).
6 Peter Grunau – Own drawing
7 Peter Grunau – Own drawing
3.0 Lashing Material and Lashing Arrangement for Containerized Cargoes
The lashing material and also lashing arrangement is in accordance to the Cargo Securing Manual, CSM, which each vessel must have. The CSM is approved by the Classification Society and has to be strictly followed. The required lashing material and also the required lashing arrangement for this type of vessel is listed and presented in Illustrations. Besides the material to be used, the handling instruction for each bay, row and tier is included, as well as the maximum stacking weight per tier for each bay.
The lashing material to be used must be in accordance to the stress acting on the container and this is different for a full container vessel of 900 TEU or a full container of 12000 TEU. Also, for ships that are certified to carry containers on deck and in the hatches but are actually no container ships, the stress is acting on different locations and is never the same.
Before we are now listing and discussing the lashing materials and their use, at first we have to understand what kind of stress is acting on the container.
3.1 Stress Acting on the Container
We have already seen that the container normally always has the same construction parts. The construction part which is actually the strongest one and can withdraw also the highest stress is the corner post. A container is designed in a way that 9 containers can be stapled on top of each other. All other parts are much weaker. Therefore, also the maximum stress acting will be mostly found on the corner post and the corner casting. Therefore, these parts of the container are reinforced and much stronger than the other ones.
Illustration 12: Allowable Forces on an ISO Container9
3.1.1 Changes of the Physical Parameter due to Different Weight Distributions in the Tier when the Vessel Rolls
Illustration 13: Forces Which Influence the Container and Lashing10
The forces which are now acting on the container and which are also varying will at the same time also have an influence on the lashing arrangement. This is already foreseen in the Cargo Securing Manual and the lashing materials including their Breaking stresses are in accordance with the CSM.
The lashing material should always have the ability to come back to its original length (see also Hooke’s Law). If the lashing material is once deformed, it will lose the holding power, vertical and transverse holding power, and is therefore useless for us.
Illustration 14: Force Acting on a Container in Different Tiers
Checking the kinetic energy in accordance with the weight distribution in the stack, we can see that the 20mt in the 6th tier has more kinetic energy at a constant velocity and acceleration than the 15mt container in the last tier. But in general, the kinetic energy is increasing with an increase of height and mass. If the Force acting on the container and the kinetic energy is increasing, the forces on the lashing material are also increasing.
Illustration 15: Homogenous Distribution in the Stack
Illustration No. 1511 is presenting a correct stowage and weight distribution in the stack resulting in a decrease of the force and the kinetic energy in the last tiers of the stack. The forces acting on the lashing will therefore also decrease.
Illustration 16: Force and P.E/K.E with Wrong Distribution in the Stack
Illustration 17: Force and P.E/K.E with Correct Distribution in the Stack12
We can see that there are nearly no forces acting on the container and, therefore, also not on the lashing arrangement in the last tiers, and that this distribution will keep a sufficient vertical and transversal holding power of the lashing system, compared to Illustration No.14 where we will face just the opposite.
It is important to calculate, nowadays done by computer, the dynamic loads acting on container and lashing material and the frames.
3.2 The Lashing Material
The IMO SOLAS A – Resolution 489(XII) requires vessels to carry onboard a Cargo Securing Manual drawn up to a standard contained in MSC/Circular 385 – 1996. This was extended to new container ships and to existing vessels in 1998. The IMO Guide lines require a Cargo Securing Manual in the form of MSC7Circular 745 superseded the MSC/Circular 385.
The SOLAS Chapter VI: Regulation 5 – Stowage and Securing states that the cargo and cargo units on deck or under deck should be loaded, stowed and secured to prevent, as far as it is possible, damages or hazards to the ship, the crew and the cargo throughout the voyage. Cargo and cargo container should be loaded, stowed and secured in accordance with the Cargo Securing Manual.
On container vessels, there are fixed and loose container lashing materials. Fixed lashing materials are the dovetail foundation, Cell-guides in the hatches, lashing rings (D-rings).
Loose container lashing materials are:
Twistlock – conventional type
Twistlock – Semi-Automatic Twistlock
Bottom cones
Double stacking cones
Single stacking cones
Bridge fittings
Linkage plates
Rack spacer
Mid stacker
Turnbuckles
Lashing rods, various length
Handling tools
Operation rods for opening the twistlock
3.2.1 Handling and Safety Instructions for Loose Lashing Material
There are handling and safety instructions for the loose lashing materials which must be known and observed.
Twistlocks must be inserted so that the opening devices are accessible for opening
All loose securing material must be applied in accordance to the approved Cargo
Securing Manual
All twistlocks have to be locked including those twistlocks located in the
Gap13 between the 20’ containers
All twistlocks should be locked in the same direction (for conventional twistlocks)
for easy operation and controlling of the locking position. Never mix left hand and
right hand conventional twistlock
Never mix the lashing systems
In case of bridge fittings with additional stances plate(s) for pressure forces, the
Pressure device(s) have to be correctly fitted (between the container corners)
If facing jammed semi-automatic twistlocks, the opening instructions should
be observed (Emergency Tool)
Damage containers are not allowed to be loaded
Tension–compression–elements, adjustable tension and compression elements
must be set with a minimum clearance to the longitudinal bulkhead. The reason
for setting this elements (will be used often times on reefer ships in the hatches)
is to reduce the movement within the container block
Semi-automatic twistlocks must be inserted in the ISO hole at the quayside, with
the yellow cone upside
Securing and un-securing of containers have to be carried out during the time the
vessel is in port at the berth.
As already mentioned, the lashing material must be in accordance to the CSM. On modern vessels, lash bridges are fitted. Lash bridges are steel constructions running athwart ships between the 40’ container bays. The 20’ containers can only take advantage of the lashing bridge at one end. If two 20’ containers will be stowed, only the forward part of the first one and the aft part of the second 20’ container can be lashed down to the lash bridge. The other two sides must be secured with twistlocks only. Therefore, the weight of each 20’ container is limited by the maximum capacity of the lashing/lashing system at the side where the lashing will be not connected to the lashing bridge. The advantage is that it allows the second and third tier container to be secured to the lash bridges, using lashing rods and turnbuckles. Another very important advantage of the lashing bridge is that it allows the anchoring points of each stack to be moved higher up the stack. The result is that the tipping moments which act on the stack when the ship is rolling will be reduced. Therefore, the lashing becomes more effective.
For the lashing of the container the most common materials are the semi-automatic twistlocks and the lashing rods/turnbuckles on deck and the cell guides in the hatches. In the hatches, there is normally, on full container ships, no securing of the container by means of lashing rods necessary as they will be guided and fixed by the cell guides.
The semi-automatic twistlocks have a big advantage compared to the conventional manual twistlocks. The twistlock will be placed already at the dockside, meaning that nobody must climb up the container stable to set twistlocks. Second of all, the loading and discharging is much faster because the unlocking of the twistlocks will be done via an unlocking tool which will be operated from the lash bridges.
Illustration 18: Lashings and Lash Bridge14
3.2.2 Cargo – Container Securing Plan
All containers stowed on board must meet the container standards. The securing system is based on the ISO container standard, if not otherwise indicated. All loose securing elements have to be applied as shown in the container securing plan. The plan must provide following necessary overview:
Must provide the correct application to the container, based on the transverse, longitudinal, and vertical forces which may arise in adverse sea and weather condition
There must be sufficient reserve cargo securing devices on board
Must present information about the strength of each securing device
Alternative stowage patterns for containers of different dimension
Must consist and provide the user with longitudinal and athwart ships views of the lashing arrangement
Must present the maximum allowable stack weight
Must provide the vertical sequences of masses in stacks
Must represent the stack heights in regards of the sight lines
Application of securing devices using suitable symbols with regards of: stack weight, stowage position, and masses in stack and stack height
Should provide information on forces induced by wind and sea on deck cargo
Should contain information of the increase of forces or acceleration with increase of the GM
All securing devices must be certified by the Classification Society the ship is belonging to.15
3.2.3 Stowage and Securing Principle
Depending on the lashing arrangement and the position of the container (loaded on deck or in the hatch), there are different forces acting on the container and also on the securing device. During the calculation of the securing system, also the strength capacity of the containers which have to be secured should be considered, as there are:
Permissible racking loads
Permissible pressure loads
Permissible post loads
Permissible vertical forces for wind exposed stacks
The lashing can be generally seen as a reinforcement of the container frames. The container lashing has to be used so that the acting racking forces in the stack will not exceed 150kN. The weight distribution in the stack is very important and does not have to be exceeded. The weight distribution stated in the securing manual represents already the optimum distribution under the given circumstances.
As a general guide line of stowing and distributing of the container we can say:
First the extra heavy weight container – then the heavy weight container – medium weight container – light weight container and in the last two tiers or the last tier only empty containers.
3.2.4 Consequences in Alteration of any of the Permissible Values
a. Alteration of Weight Concentration in the Stack
An alteration of the weight downwards is possible, an upwards alteration of weight concentration is not possible. If loading a heavy weight container in the last tier, a continuous upgrading of the weight in each tier will be the consequence and will result in a tilting of the stack, an overstress of the foundations, twistlocks and lashings. Especially in the outer stacks the stack weight is less than elsewhere. Exceeding the stack weight will have severe consequences.
In general: an exceeding of the stack weight is not allowed.
b. Maximum Quantity of Tiers
The maximum quantity of the tiers should not be exceeded. If this will happen, the force acting on the securing system will increase and also the sight line could be interrupted.
c. Weight Distribution
The weight distribution in the container securing manual is based on 8’6’’ containers. For this reason it is not easily possible to stow a high cube container or any other heavy weighted container on top if this is not in accordance to the cargo securing manual. If I change the weight distribution in the stack – upwards change, the C.G will move upwards causing a decrease of the GM. Further, the securing system of the container will be overstressed, the forces are increasing. Avoid stowing loaded containers in the last tier(s).
d. Specific Features to be Considered
Each container can be considered as an outer stack container. The container should be lashed accordingly and, if necessary, the weight should be reduced in the stack. In case different stack heights are present (left side 6 high and right side 3 high), these containers have to be considered as outer stack container as well and have to be secured accordingly.
3.2.5 Cases Which Have to be Avoided when Stowing Container
a. The Maximum Stack Weight is Exceeded.
The maximum stack weight should never be exceeded because of:
Overstress of hatch cover construction
Overstress of stowage and securing material
Overstress of containers
Consequence: Loss of container
b. The Given Weight Distribution in the Stack is Exceeded
Overstress of stowage and securing material
Overstress of container
Consequence: Loss of container
c. Not Locking of Container Twistlocks
Consequence: Loss of container
d. Lashing not Foreseen With the Container Securing Manual
Overstress of twistlocks
Loss of container
e. The Pretension in the Lashing is Exceeding 5 kN16
Reduction of the loading capacity of the securing system
Extreme cases should always be avoided not to damage or lose the container.
The securing arrangement of the container should also be discussed with the stevedores because it might be necessary to set additional lashing for expected bad weather conditions during the voyage (expected tropical revolving storms etc.). Always be reminded: On board, the ship master is responsible for the cargoes loaded and their maximum security. Additional assistance can be also asked from the company’s supervisor for this ship.
3.2.6 Types of Container Damages and Lashing Failures
If ships are in navigation, they encounter three main movements: pitching, rolling and heaving. These movements are also acting in form of acceleration on the container and container lashing system. Out of these movements, the separation force –tipping force, is also acting on the container and its lashing system.
a. Twistlocks are Broken:
The ship is rolling heavily resulting in an increase of the separation force. This can cause that the twistlocks will be pulled out of the corner casting, that the twistlocks break or that the corner casting is separated from the container body.
b. Damages due to Racking Force:
This occurs if a heavy container is stowed in one of the higher tiers. If the ship is rolling heavily, a racking force will be set up in the frame of the lowest container, resulting in an overload of the container frame and lashing. As a general rule, it can be considered: The larger the roll of the ship the larger the racking forces.
c. Damages due to a Large GM
If a vessel has a large GM, it tends to have a short rolling period. This short rolling period will increase the dynamic loads and as well all other forces will also increase like compression and tension force. This will lead to the result that the forces acting on the corner post will increase drastically and also the forces acting on the twistlocks. This might lead to a structural damage of one or more corner post and can lead to the loss of the container.
d. Damages due to Overloading the Stacks – Bad Stowage
One of the most persisting problems is the stow of heavy containers on top of very light ones or stowing of heavy containers in the last tiers, ignoring the cargo securing manual and all forces which will, as a result of it, increase. The bad stowage can have several reasons:
Inexperience of planner and ship crew
Insufficient knowledge of planner and/or ship command
Late arrivals of the container in port
The consequences are more or less very drastic and can lead to capsizing of the vessel. In the Illustration below, the changes can be recognized:
Illustration 19: Force Acting in Different Tiers if Stowed Incorrectly17
This situation can be avoided. The master and all his officers must check the bay plan prior loading and must decide if the cargo planning done by the planner ashore is acceptable.
