01. Steel manufacture

 

Steel is manufactured from iron during a process in which most of the iron’s carbon is removed, producing a tougher and more ductile material.

 

Steel is smelted from iron ore in a process involving heat, coke, limestone, oxygen and scrap steel. Manufacture takes place in a furnace, of which there are two types in common use: the basic oxygen furnace and the electric arc furnace.

After leaving the furnace, the hot steel passes through a secondary steel-making process to improve its quality, before it is cast into slabs, ingots, billets or blooms. The process of casting steel slabs, ingots, billets and blooms is known as continuous casting, because the process never stops. If the steel mill has rolling equipment, the hot metal may be rolled rather than cast.

 

Slabs, ingots, billets and blooms are often shipped by sea in transit to a rolling mill where they can be rolled into long products such as profiles, beams and channels. Steel slabs are rolled into plate.

 

 

 

There are two rolling processes – hot and cold rolling. Hot rolling takes place when the steel is red hot and cold rolling after cooling. During hot rolling, the steel product is formed. During cold rolling, the product is improved and made ready for sale.

 

Hot metal and reheated steel slabs can be hot rolled to form strip steel, a thin sheet of steel up to 2m wide. Strip steel can be coiled for storage and shipping. Steel that has been rolled when hot and coiled is known as a ‘hot-rolled coil’.

 

 

Hot-rolled steel coils may be unwound for further rolling, only this time the metal will be cold and the process is called cold rolling. Cold rolling is the final step in steel manufacture – after cold rolling, the steel is ready for use. Cold-rolled thin sheet steel could be coiled again to create a ‘cold-rolled coil’.

Cold rolling improves the steel’s surface quality in readiness for sale.

Hot and cold-rolled steel coils are frequently shipped by sea. Even though some, but not all, hot-rolled coils will undergo a further manufacturing process, it is important for them to be delivered free from excessive rust and/or physical damage. Cold-rolled steel coils will not be further processed and when unwound can be used to make steel panels, such as car body parts. Cold-rolled steel coils need to be delivered to receivers in pristine condition.

 

02. Basic advice

 

 

 

The following checks and actions should always be taken when carrying steel:

 

 

 

Stowage

 

•      Read your company’s instructions on the safe carriage of steel, your ISM requirements and the advice in the cargo stowage and securing manual. Cross-reference with industry publications such as the Code of Safe Practice for Cargo Stowage and Securing and Thomas’ Stowage. This guide may also form part of the ship’s cargo manual.

 

 

 

•      Find out the proposed loading plan in advance. Check whether the best, rather than the easiest, stow is proposed. If loading steel coils, check that key/locking coils are correctly positioned and tank top point loads are not exceeded. Estimate the loaded metacentric height (GM) by using the correct vertical centre of gravity for the loaded steel. Avoid very high GMs. Bear in mind the likely weather to be encountered during the voyage, as high GMs are associated with heavy/violent ship rolling.

 

•      Enquire into the proposed method of stowing and securing cargo. Meet with the stevedore superintendent and/or supercargo to discuss the loading plan. Use this as an opportunity to point out any limitations with the ship or its equipment.

 

•      Mark the holds’ strong points, such as solid floors, on the tank top. Extend the marks up the hold sides. These are the best load-bearing positions. Marking them will make it easy to check whether cargo and dunnage are correctly positioned during loading.

 

•      Avoid stowage in spaces without parallel sides. If this is unavoidable and frequent loadings are expected, arrange for the space to be permanently ‘squared off’ with a steel buttress or heavy-duty timber. Pay special attention to No. 1 hold.

 

•      Avoid loading steel in the same compartment as chemicals, fertilisers, sulphur or other cargoes that could cause damage.

 

 

 

Dunnage

 

Apply dunnage to:

 

-      spread the load. Always use sufficient strips of dunnage to avoid exceeding the tank top acceptable point load. As the height of a stow increases, so too does the requirement for additional strips of dunnage

 

 

 

-      create frictional resistance. Steel has a very low coefficient of friction. Metal-to-metal contact should always be avoided

 

-      avoid deformation of the cargo, especially when loading steel plate, coils and railway lines -    protect steel from moisture

 

-      reduce possible movement within a stow, especially when carrying steel plate or slabs

 

-      fill gaps, unsupported ends and breaks in block stowage.

 

•      Laying dunnage is an important part of the safe and efficient carriage of steel. Use dunnage of sufficient thickness to enable efficient weight distribution and to facilitate cargo lashing/handling. One inch thick softwood dunnage is often used with steel coils. However, this thickness of dunnage is unlikely to give an even distribution of weight, and a point load should be assumed during calculation of loading limits and tank top strength. To avoid the risk of point loads, use a thicker dunnage (see Figure 13 on page 19). Ship’s officers should ensure the correctly sized dunnage is laid properly. When placing dunnage between flat steel plate, keep the dunnage in a vertical line to avoid plate distortion. Use dunnage sized 60mm by 80mm.

 

•      Use wooden wedges to fill gaps between dunnage and steel, and within the stowage.

 

•      Use only dunnage certified for ship use, that is, dunnage with a plant quarantine stamp. In some ports, officials will want to inspect dunnage certificates. Avoid using dunnage that has previously been used with steel products, because the dunnage’s cellular structure is likely to have altered. Recycle used dunnage in an environmentally acceptable way.

 

 

Loading

Coils should be stowed across the ship, on stout dunnage, with their axes fore and aft. Use wedges to safely locate coils during loading. Base coils should be loaded from the ship’s side inwards to the centre and wedged, with the wedges placed below the coils on their in-board side. Once at sea, the ship’s motion will cause the coils to settle as the weight of the key coils tightens the stow. Wedges placed either side of a coil will prevent this. However, when more than one key coil is used, and to locate the position of the key coils during loading, double wedging is necessary on either side of the centre supporting coil(s).

Coils should be stowed across the ship, on stout dunnage, with their axes fore and aft. Use wedges to safely locate coils during loading. Base coils should be loaded from the ship’s side inwards to the centre and wedged, with the wedges placed below the coils on their in-board side. Once at sea, the ship’s motion will cause the coils to settle as the weight of the key coils tightens the stow. Wedges placed either side of a coil will prevent this. However, when more than one key coil is used, and to locate the position of the key coils during loading, double wedging is necessary on either side of the centre supporting coil(s).

Coils are secured with steel banding to each other in varying forms. Pneumatically tightened steel bands, which bind the coils to those stowed immediately below, are preferred.

Key coils are positioned so that their bottom edges are one-third of a coil’s diameter below the top of the coils in the tier being locked, in a gap that is not greater than 60% of the key coil’s diameter.

Wire coils should be stowed vertically, with their axes fore and aft, adjacent to each other in a similar configuration to the stowage of steel coils.

Plate should be stowed in the fore and aft direction, with dunnage running athwartships and between each tier. Stowage should be from one side of the ship to the other, leaving no voids, and the top layer secured with wire or  chain bindings. When loading thin plate, stowage in subsequent tiers can be in alternate directions.

 

 

Long products, such as pipes, channels, angles, beams, flats, rounds and rebars, should be stowed in the lower holds in the fore and aft direction, with dunnage placed athwartships. Avoid mixing products of different types and lengths in the same stow. Place dunnage between the tiers. The top tier should be secured to the ship.

 

 

 

Semi-finished      steel      slabs should be stowed in the same manner as steel plate. California Steel Industries (CSI) recommends vertical stowage with tight lashing of top tiers (see page 26 – California block stowage).

 

•      Arrange a preloading survey of all finished steel before loading. Do not confuse finished steel with project cargo.

 

•      Avoid loading wet steel and wet dunnage. Wet steel has less friction. Both give off moisture.

 

•      Ship’s officers should monitor stevedores to ensure:

 

-      they use the correct equipment and do not damage the cargo. Steel wire slings or chains when used incorrectly can damage bundles of

 

pipe, plate or steel coils

 

-      steel is not handled roughly

 

-      forklifts are fitted with proper lifting tines. Damage during lifting by a forklift is very common

 

-      stowage and securing is as per the cargo plan and the ship’s cargo securing manual

 

-      cargo is not loaded wet or during periods of rain or left exposed in wet conditions

 

-      details of cargo damage are correctly recorded on the stowage plan and in the cargo log.

 

•      Ship’s officers should monitor the surveyor performing the preloading survey and be available to assist.

 

Cargo securing

Lashing arrangements that do not include a vertical component and do not connect to the ship’s structure are of little value. However, in practice, steel is often lashed to itself with loop lashings. For example, steel coils loaded two tiers or more are secured to each other. Their key coils are secured with tight steel bands to the coils immediately below. Coiled wire has its top layer banded to the next layer down. Plate is held with horizontal wire bands across the top layer in an ‘x’ shape. Here, the objective is to create an immovable cap

 

 

Cargo care

 

Steel cargoes are easily damaged by salt water. Before loading, test hatch covers for weathertightness and repair the covers if leakage is found. Test with ultrasonic hatch cover testing equipment. Examine hold and bilge wells and make sure they are dry. After loading and before closing hatch covers, clean drain channels and check that non-return valves are free. When closing hatch covers, apply cross-joint wedges before hatch skirt cleats. For further information on the maintenance of cleats and the closing of ship’s hatch covers, see the club’s publication A Master’s Guide to Hatch Cover Maintenance, which is available on the club’s website.

 

Additional protection, such as sealing foam and tape, can be applied along hatch cover cross-joints in exposed areas of the ship and especially on No. 1 hold if the ship does not have a forecastle. Ballast water should not be loaded in wing tanks when cargo holds are loaded with steel products, except when necessary for stability purposes, when load lines permit and when ballast tanks (including associated filling/ ventilation/sounding pipes) are watertight. When testing steel surfaces for chlorides (salt) using silver nitrate, a resulting milky solution shows the presence of chlorides.

 

It does not necessarily show that sea water has entered the hold either through hatch covers or the hull.

 

During the voyage, control the dew point in the cargo hold by ventilation or by dehumidifying the air.

-      Fit dehumidifiers in holds when steel is loaded in winter or in cold conditions for discharge or passage through areas in summer/warm conditions. Dehumidify holds as the outside air temperature rises. Particular care is needed when loading in humid tropical conditions, because cargo holds will contain damp humid air. Dry the air with dehumidifiers.

-      Make sure dehumidifier cabling does not compromise the integrity of the hold or pose a fire hazard. Dehumidifiers drain directly to hold bilges, which should be pumped dry regularly. Keep records of bilge pumping operations.

-      Take daily dew point temperatures of hold and outside air with a wet and dry bulb thermometer. Ventilate when the dew point of the outside air is less than the dew point of the hold air. This will normally occur when cargo is loaded in warmer conditions for delivery to a port, or passage through an area, with colder conditions.

Keep detailed records of hold and outside air temperature, at the load port, during the voyage and at the discharge port. Record times of hold ventilation and of heating fuel in tanks adjacent to holds loaded with steel

 

 

 

03. Steel commonly shipped by sea

Finished steel products

 

Type	Description	Usual stow	Notes	Survey required
Cold-rolled coils	Finished sheet steel in a transportation coil. 2 to 28 tonne weights	Athwartships – bottom stow	Coils will not be further processed but unwound and used	Yes
Hot-rolled coils	Sheet steel being transported to a rolling mill in 2 to 30+ tonne weights	Athwartships – bottom stow	Coils usually unwound and cold rolled	Yes
Coiled wire rod	Long steel bars formed by hot and cold rolling	Fore and aft	Can be damaged/ squashed by high stows. Can be left on the quay and loaded in the rain	Yes
Profiles	Long steel bars formed by hot and cold rolling	Fore and aft	Used to reinforce steel structures	Yes
Channels	Long steel bars formed by hot and cold rolling	Fore and aft	Used to reinforce steel structures	Yes
Angles/bulbs	Long steel bars formed by hot and cold rolling	Fore and aft	Used to reinforce steel structures	Yes
Girders	Long steel bars formed by hot and cold rolling	Fore and aft	Used to reinforce steel structures	Yes

 

Figure 3: Finished steel products

 

	Type	Description	Usual stow	Notes	Survey required
	Plate	Thick steel in finished form after cold rolling	Fore and aft or athwartships in bundles	Used in the manufacture of all sorts of steel structures	Yes
	Reinforcing bars (rebars)	Hot-rolled steel bar with a rough finish	Fore and aft	Used to reinforce concrete	No
	Smalldiameter pipes	Finished steel loaded in bundles	Fore and aft – often pre-slung	Top tier lashed and secured	Yes
	Largediameter pipes	Finished steel loaded singly or in bundles	Fore and aft	Ends prone to contact damage	Yes
	Coated steel pipes	Finished steel loaded in bundles or cradles	Fore and aft	High value. Easily damaged by rough handling	Yes
	Sheet piling	Used in construction industry	Fore and aft	Not usually further processed	No

 

Type	Description	Usual stow	Notes	Survey required
Ingot	Raw steel before rolling	Fore and aft	Processed to make steel bars and plate	No
Slab	Raw steel before rolling	Fore and aft	Processed to make steel bars	No
Bloom	Raw steel before rolling	Fore and aft	Processed to make steel bars	No

Billet

Raw steel before rolling

Fore and aft

Processed to make steel bars

No

 

04.  Steel cargo surveys

Shipowners have an obligation to cargo receivers to deliver cargo in the same apparent condition as loaded (shipped).

 

Finished steel products can suffer physical damage or rusting during transit from the steel mill to the port, or during storage at the port.

Finished steel is most problematic because, at the discharge port, it is difficult to determine whether the damage occurred before loading or while on board. Consequently, it is essential to examine finished steel for defects before loading and to identify and record any damage or rusting. This information is needed to prove to cargo receivers that such damage occurred prior to shipment and not on board the ship.

P&I clubs arrange preloading surveys of finished steel as a means of preventing shipowners facing damage claims where damage occurred before loading. The club’s rules require the survey as a condition of cover:

 

 

Unless the board otherwise determines, there shall be no recovery in respect of liabilities arising out of the carriage of finished steel products, unless the member has arranged for a preloading survey to be carried out by a club-approved surveyor at each port of shipment, Finished steel includes:

 

•      hot or cold-rolled steel coils

 

 

•      steel wire coils

•      steel plate, bars, profiles, channels,

 

 

•      angles and joists

 

•      sheet steel

•      steel pipes. 

•      semi-finished steel slabs

•      scrap steel

•      steel rebars and D-bars*

 

•      project cargo and/or flat-packed steel structures.

•      semi-finished steel slabs

•      scrap steel

•      steel rebars and D-bars*

 

•      project cargo and/or flat-packed steel structures.

Survey procedure

Preloading steel surveys are usually undertaken by surveyors appointed by the P&I club. The surveyor has a number of duties, the most important is to examine cargo for damage and to advise the master on suitable clauses to endorse on the mate’s receipts and bills of lading.

However, surveyors should also examine the ship’s hatch covers, cargo holds and observe stowage, pointing out to the master any hatch cover defect that could give rise to leakage and any aspect of stowage that appears incorrect

The surveyor should never take charge of stowage – this is the master’s responsibility. However, if the master requires guidance and support in relation to stowage, the surveyor should be specifically instructed to advise on this issue, with the surveyor’s fees to be for the member’s account as this is an operational matter. The club can assist with identifying and instructing a suitable surveyor for stowage issues.

When examining steel cargo, surveyors will be checking:

where the steel was manufactured, how the steel was transported from the steel mill to the port, where the steel was stored in the port prior to arriving at the •      berth and how the steel is protected from damage and the elements

 

 

•      for physical damage, rusting, wetting and possible contamination with salt and/or chemicals. For example, steel stored close to the sea, or delivered by barge, can become contaminated with windcarried salt.

 

At times, the steel itself cannot be examined because of its packaging. In which case, the surveyor will pay close attention to the condition of packaging and whether this is damaged, missing or wet.

 

 

 

 

Figure 6:  Steel cargo loading

 

When examining stowage, surveyors will check that:

 

•      steel is positioned correctly, on correctly sized and laid dunnage

 

•      locking coils are positioned correctly • stowage gaps and free ends are secured with dunnage

 

•      lashings are applied correctly.

 

When examining hatch covers, surveyors will check:

 

•      sealing gaskets and drain channels for damage

 

•      that drain channels are clean

 

•      cleats and wedges for missing springs and damaged compression washers

•      that drain channel non-return valves are free.

The surveyor will want to:

•      examine steel while it is in storage in the port, noting storage conditions

•      examine each parcel of steel on the quay before loading. Otherwise, the examination will take place in a marshalling area

•      note any exceptions with the steel, carefully describing the damage and identifying the damaged steel by reference to plate numbers and/ or identification tags. Later, it will be necessary to endorse bills of lading and mate’s receipts with details of the damage. Suggested wording is contained in this guide. At times, the surveyor will recommend not to load badly damaged cargo.

Occasionally, the surveyor will ask for assistance from the duty deck officer. This may be because:

•      cargo is being loaded in more than one hold at the same time

•      cargo is being loaded during a 24-hour period, but loading is erratic and intermittent

•      the surveyor is checking other cargo and recording details of damage as loading continues.

The duty deck officer should always provide assistance.

When recording details of the cargo’s condition, surveyors should always make detailed notes of any damage seen regardless of whether it is damaged packaging or very minor blemishes on the cargo. Everything needs to be accurately recorded by the surveyor. At times, the steel may appear to be in ‘typical condition’ for the type of cargo, even though there are minor blemishes. However, if the steel is in less than perfect condition, the true condition of the steel should be recorded by the surveyor and itemised in his report. The description needs to be precise because it may be necessary to prove to the receivers the exact items that were damaged, using the steel mill’s identification marks or the shipper’s docket, so that the receivers can verify that the items found damaged are the same as those noted by the surveyor. Never report, for example, ‘150 bundles of steel bar were loaded and 95 had minor rust/damage’. It is necessary to identify the 95 bundles

Surveyors who come on board at the discharge port may represent receivers, in which case, their credentials should be checked and approved before allowing them access to cargo. Allow only surveyors whose credentials have been approved to take photographs of cargo.

 

There will be occasions when an independent tally of coils will be required. Ask the surveyor who is conducting the preloading survey whether they can assist.

Silver nitrate testing

Silver nitrate tests are performed as a means of detecting chlorides, in this case salt (sodium chloride). Silver nitrate is a clear solution, which goes milky white when mixed with chlorides.

This test is made whenever there is an allegation that steel has been damaged because of contact with salt water. If the test is positive, claimants are likely to pursue a cargo damage claim.

Test procedure

•      The silver nitrate solution should be kept in a dark bottle fitted with a dropper.

•      Before testing, check the area being tested for contamination.

•      Squeeze a few drops of the silver nitrate solution onto the wet or rusty area, ensuring that the fluid does not come into contact with hands.

•      Observe the result. The solution will change colour quickly and markedly when there is a strong presence of chlorides.

•      Ensure that the dropper does not touch the wet or rusty steel or hands. This may affect future results.

 

Positive results show that chlorides are present on the steel. It does not show that sea water entered the hold either through hatch covers or the hull.

Chlorides can be present for other reasons, including:

•      the hold was washed with salt water and not finally rinsed with fresh water.

•      wind-blown salt accumulated in the hold and condensation caused salty water to drip onto the cargo

 

•      salt was deposited on the steel before loading. Surveyors undertaking a preloading survey should check for salt contamination.

At the start of the voyage, it is important to ensure that hatch covers are weathertight, that the bilge system is tight, that holds are free from salt water residue or dry salt, and that any salt contamination found on the steel prior to loading is accurately recorded on the bill of lading.

 

If chlorides are found, it is important to advise the shippers as soon as possible. The bills of lading and mate’s receipts will need to be endorsed, and shippers may wish to separate the affected cargo.

Rusting is often described by reference to a percentage of the surface affected. This can be very difficult to quantify in practice. Rust percentages can vary from piece to piece, for example, one side of a beam may be totally rusty and the other side may not be rusty

at all. The International Group of P&l Clubs standard clauses for steel can be broadly broken down into three categories:

•      rust spotted – up to 15% of the visible surfaces affected by rust

partly rusty – 15%-75% of the visible surfaces affected 

 

 

 

 

 

The bill of lading represents the cargo itself, and possession of the original bill indicates who is entitled to receive the cargo at the discharge port. A bill of

lading is a record of the quantity of cargo on board and of its apparent order and condition at the time of shipment. As such, it is a vitally important

document. Cargo damage or shortage claims can arise as a result of errors on a bill of lading 

 

The description of cargo on the bill has to accurately reflect the condition and quantity of cargo loaded. Any cargo defect or damage that may exist prior to loading needs to be accurately endorsed on the bills before they are signed. If the bills are not seen on board, a description of the damage should be endorsed on the mate’s receipt.

•      by rust

•      rusty – over 75% of the visible surfaces affected by rust.

Use these categories if unable to estimate a percentage

Clauses

The following or similar clauses should be used to describe damaged steel on bills of lading:

	Description
	Flat bound steel plate reference number xxxx rusted xx% of its surface and buckled along its edge
	Profile reference number xxxx – flanges/webs/corners/edges – bent/buckled/ distorted, along xxxx of its length
	Coil reference number xxxx – ripped/torn/distorted – along/in/around xxxx position
	Plate/bar/channel/profile reference number xxxx – dented/pitted in xx places and along xxx% of its edge
	Plate/bar/channel/profile/ coil – reference number xxxx – loaded in wet/damp/ rain/snow/ice conditions before shipment
	Plate/bar/channel/profile/ coil – rust spotted/partly rusty/rusty before shipment
	Plate/bar/channel/profile/ coil – rusted xxx% overall

 

Figure 7: Clauses

 

06. Steel coils and ship’s strength

Carriage of a high-density cargo such as steel presents a challenge during ship design to ensure the ship’s hull is sufficiently strong

 

Class rules

Since 2006, many bulk carriers and some dry cargo ships have been built to common structural rules. The latest being Common Structural Rules for Bulk Carriers and Oil Tankers (CSR-H), 2017. The relevant sections which apply to loading steel coils are:

•      steel coil loads in cargo holds of bulk carriers – part 1, chapter 4, section 6.4

•      structures loaded by steel coils on wooden dunnage – part 2, chapter 1, section 4.

The common structural rules deal with loading on the ship’s structure and the minimum scantling requirements to resist it. Through them, ships are designed for specific loading conditions, in which homogeneous (constant load per area t/m2) cargo loads are often assumed. The CSR sections referred to above contain a methodology to assess scantlings for steel coil loads. However, these scantlings are based on the assumption, in the case of loading steel coils, that the hold is loaded with coils of the same size and weight. These cargo loads as well as the wave loads contribute to the global bending, torsion and shear that the hull girder needs to withstand. The loading conditions will be in the ship’s loading manual or computer, but these conditions are likely to reflect uniform loading of a similar sized and shaped cargo. In loading mixed steel of various sizes and shapes, particularly coils, is common. In which case, care is needed to avoid overloading the tank top.

Stowage

 

Coils are usually stowed athwartships and locked with one or more key coils. When carried more than one row high, the weight of top coils passes down to the ship’s structure through the points where the coils touch. We assume that all the weight is passed vertically down to adjacent coils, when in fact, there is a tendency for key coils to push adjacent coils apart, creating a small horizontal force (see Figure 9). This horizontal force is resisted by the hold side or lower hopper and friction between the coils, dunnage and cargo hold. The vertical force is resisted by the tank top and double bottom. Double bottom structures are specially designed to withstand cargo load. Their plating and secondary stiffeners carry load to the primary structure. They are a grillage structure consisting of a longitudinal and transverse structure, with solid floors and transverse webs in lower hoppers.

 

 

Friction between coils is negligible. When calculating the vertical force, it is assumed that force is transferred perpendicular to a coil’s surface along a line drawn centre to centre (see Figure 9).

 

Using this assumption, support forces in an arbitrary stack of coils can be calculated. Figure 10 shows two examples of a single coil supported by two coils on the bottom tier. On the left, the coils on the bottom have the same diameter and, hence, the weight of the top coil is shared equally between them. However, on the right, the majority of the weight of the top coil is supported by the smaller coil on the bottom tier, resulting in increased load passed to the inner bottom.

 

This approach can be followed to determine the loads on the inner bottom for irregular coil stacks, an example of which is visible in Figure 11.

 

Inner bottom and hopper strength

 

The effects of the steel coil loading and the potential for point loading, compared to a homogeneous loading, can be visualised by finite element analysis.

 

If we consider single tier coil loading with two key coils per row, as shown in the diagram on the right, there are two possible loading distributions:

 

1.    Loading as weight spread equally over the inner bottom such that a homogeneous pressure load is generated, as shown in Figure 12a.

 

2.    Loading as weight spread unevenly over the inner bottom, such that there are point loads, as shown in Figure 12b.

 

In practice, actual loading is localised rather than homogeneous and, as such, uneven loading on the inner bottom is common.

 

In this example, the coils are placed on three pieces of approximately 6in by 1in dunnage, spread evenly. The resulting stresses in the ship’s inner bottom are shown in the finite element analysis (right), with the bottom right diagram illustrating the stress from point loading associated with uneven cargo distribution.

A ship’s inner bottom is designed for homogeneous loading and, for this reason, the avoidance of point loading is imperative. Dunnage is inserted between the steel cargo and the ship’s hold structure. The dunnage protects the cargo during stowage and transport from damage, as well as providing support and friction between the cargo’s load and the ship’s hull. Increasing the number, width and thickness of dunnage will increase the spread of loading. However, the actual load distribution effect will be limited and an evenly distributed load is never achieved. Consequently, using the correct type and size of dunnage to reduce the risk of point loading cannot be over emphasized. Point loading is reduced by using dunnage thicker than 1in– thicker dunnage increases the load spread 

The analysis above shows that assessing forces from a steel coil stow by assuming equivalent uniform loading is not advisable, as in reality, the loads are very concentrated, leading to higher stresses in the double bottom than would be expected. The CSR rules can be used for guidance during ship design for specific steel coil loading conditions. However, many of the ships used in the steel trade that carry coils have limited steel coil loading conditions in their loading manual. Calculation of conditions that reflect actual loading is essential to maintain the required level of safety.

 

07. Principles of stowage

Steel is shipped in a variety of shapes, sizes and weights. Consequently, it is difficult to stow in classic block stowage. Careful preparation of the hold is essential

When loaded in a ship’s hold, steel is placed on dunnage. Dunnage is placed between successive tiers of cargo and the side shell or lower hopper. Dunnage has two functions. To spread the steel’s load uniformly in relation to the ship’s structure and to provide frictional resistance. Insufficient or incorrectly applied dunnage can result in high point loads on the ship’s tank top, possibly deforming it. It is important to use dunnage of the correct thickness, see Figure 13, page 19. When possible, lay dunnage on strong points. In Europe, dunnage is available in a mixture of imperial and metric sizes, with 8in by 1in planks used with steel coils, 60mm by 80mm planks used with steel plate and bars, and 6in by 4in planks used with heavy steel. Elsewhere in the world, dimensions are similarly either imperial or metric.

Steel is generally loaded in the fore and aft direction, with part cargoes loaded forward from aft. When loading coils, wedges are used below the coils, placed longways side down on the coils’ in-board side. They locate a coil as it is stowed and prevent in-board athwartships movement. A key coil will always be used to lock a row of coils, with the key coil in subsequent rows placed in a different position. Key coils take up any gap that may occur between coils during ship movement.

Wedges are always placed on dunnage and never directly on the tank top.

Coils are stowed in rows or tiers. During loading, they are generally placed in the hatch square before stacking with a forklift. As each successive row or tier is completed, the coils are lashed before the next row or tier is loaded. A small gap is left between each successive row. The hold area used for landing coils and the stowage location have to be free from debris and/or raised objects. Landing a coil on a bulldog grip, ring bolt or shackle will cause considerable damage to the coil.

 

When lifting coils with a forklift, only forklifts with a coil-friendly tine, ie those fitted with a single central lifting arm, should be used. Even with this lifting arrangement, coils can be damaged.

A forklift carrying a large heavy coil will put a significant load on the tank top, so check and make sure the tank top strength is not exceeded. A forklift capable of lifting a 20-tonne coil will itself weigh much more than 20 tonnes.

Steel is lashed using wires, chains and steel bands. Pneumatically tightened steel bands are preferred for coils. When using wire lashings, suitable chafing pieces should be inserted between the lashing and the steel’s edge. Insert dunnage between the lashing and the steel’s sharp edges. Standing faces of coils are lashed (banded) back to the second row.

To allow access for lashing, coils are usually stowed with a 20cm to 30cm gap between rows and/or a transverse bulkhead.

The lashing procedure for coils involves securing the top coiI to the coiI immediately below, rather than securing the entire stow to the ship. By this method, the top coils act as a cap holding the remainder in place.

Profiles and plates are secured by a variety of methods, with the objective of preventing initial movement. With the exception of coils, lashings that do not ultimately connect to the ship’s structure will be of little value.

When assessing the value of lashings, it is necessary to consider how the cargo has been stowed, the potential for movement and how movement is prevented.

Frictional resistance is the principal means by which movement is suppressed.

During loading, the ship’s cargo officers must maintain a diligent watch and record cargo activities during the watch. Good records can prevent and reduce certain claims, and support any clauses made in the mate’s receipts and bills of lading.

The watch officer should report to the master and note in the cargo record book:

•      any cargo damage or broken bands on packaged cargo

•      any stevedore damage to the ship

•      the cargo condition

 

•      departures from the stowage plan

•      size and type of dunnage and how it was laid

•      instructions given to stevedores and/or lashing gangs

•      times when hatches were opened or closed

•      stoppages due to weather

•      movement of forklifts and other loading equipment in and out of the hold.

Photographs of cargo should always be taken.

 

Ports that specialise in steel have skilled stevedores and specialist equipment for stowage and securing. Greater vigilance is needed if loading or discharging in non-specialist ports.

Round products – coils

 

When coils are loaded horizontally in athwartship rows, locking the tier is essential. This is done by placing a coil to force those beneath it into a tighter stow. This coil is known as a key or locking coil. A key coil is most effective when placed at the centre of a row. However, it is important to avoid a continuous line of weight on the ship’s tank top and, consequently, key coils placed in subsequent rows are staggered. Great care needs to be exercised when placing key coils. Figures 15 and 16 demonstrate how key coils should be placed.

Key coils are placed so that the coil’s bottom edge is one-third of its diameter below the top of the coil(s) being locked. This corresponds to the gap between the coils being locked of about half the key coil’s diameter. However, if the gap is greater than 60% of the key coil’s diameter, then the key coil could be damaged or crushed. In which case, the stowage will need to be altered by repositioning coils and placing timber between the ship’s side and first coil – as shown in Figure 19. Although it is not considered good practice, two key coils can be fitted, provided they are kept separated and their weight does not fall on a coil common to both key coils

When a key coil is placed above different-sized coils, as in Figure 20, the smaller coil takes the most weight. Care is necessary to avoid crush damage to the smaller coil.

Except when strength calculations restrict loading, steel coils should be loaded in a minimum of two tiers or layers.

 

 

Stevedores may attempt pyramid loading, a method that should be avoided, because excessive weight can be transferred to the ship’s tank top and because it is difficult to lash pyramid coils.

Coiled wire rod

Coils of wire rod are stowed in a tight block stow, with their cores fore and aft on plywood sheets placed on wide dunnage. Direct contact between the coils and the ship’s tank top should be avoided. Wire coils are wedged to avoid movement. Standing faces should be avoided, but if this is not possible, lash the coils back to a bulkhead by passing a wire through their core.

 

Care should be taken when lashing with chain because chain can damage steel. Damage can be prevented by placing dunnage at the point where the chain contacts the steel.

After loading, wire coils will settle and mesh together, and no further lashing is necessary, except for those coils that are not held in a block stow.

When cargo is locked together, care is needed during discharge to avoid damage. Inform stevedores at the discharge port of this requirement.

Flat products – plates and slabs

Steel plates are generally stowed with their longest axis fore and aft, on dunnage laid athwartships. Cargo is loaded from the hold’s side to its centre. Dunnage is placed between adjacent plates to provide frictional resistance because the coefficient of friction between two flat steel plates is effectively zero.

Long plate is susceptible to waviness. Sufficient rows of 60mm by 80mm dunnage, placed vertically in line, are needed to prevent distortion. The higher or heavier the stow, the greater the number of pieces of dunnage required to support the plate and prevent buckling. In addition, dunnage has to be sufficiently thick to facilitate cargo handling and lashing.

 

Gaps between parcels of steel plate have to be chocked with strong timber. Any wooden structure built to support steel has to be self- supporting; otherwise, the structure could collapse if the cargo moves.

 

prevent initial movement.

A variety of methods are used to secure steel. Here is some general guidance:

•      Always consult the ship’s cargo securing manual before applying lashings.

•      Lashings are not designed for the most violent storms encountered at sea.

•     

The purpose of lashing cargo is to prevent initial movement. The majority of restraint comes from frictional resistance between the steel and dunnage.

•      Smooth-surfaced steel and wet steel have almost no frictional resistance.

•      It is only slabs stowed using the method known as California block stowage or steel coils that are secured to themselves; otherwise lashings should be secured to the ship’s structure.

•      Long products and plate may be intermediately lashed to themselves in order to bundle the steel together and produce a tighter stow.

•      Lashings placed across the top of the stow are of no value. Lashings around a stow serve only to hold the steel in a block.

•      Loosely fitted lashings serve no useful purpose.

•      Steel wires and chain can cause damage if applied directly and if they touch the steel being lashed.

•      Insert dunnage between steel and the lashings to increase friction and to prevent damage.

The disadvantage of lashing with wire and steel bands is that they cannot subsequently be tightened to compensate for dunnage compression, shrinkage or movement. However, this risk is minimised when bands are tightened pneumatically.

Friction

Friction is important as it prevents cargo movement during ship rolling. The table below shows the coefficient of friction for smooth plate. It is interesting to note that wet steel-to- steel surfaces are considered to have no friction at all.

Steel with a rough finish will have a higher value than the materials listed below.

Friction  coefficient            table      for          smooth  plate

 

Materials in contact

Friction                 coefficient

 

claims, and structural damage to the ship.

 

•     

all damage to finished steel cargo is noted and presented by the master to the shipper’s or receiver’s agents, as quickly as possible. If the P&I club steel surveyor is attending, pass details of the damage to him as well

•      assistance is provided to the appointed steel surveyor during a preloading survey and the survey is carried out in a diligent manner, with discrepancies reported to the master

•      lashing and stowage are carried out as per the cargo plan. It is vitally important for the safe carriage of cargo and for ship safety that steel is loaded in the proper manner. If it is not, it should be reported to the master and owner/charterer immediately

•      a log is kept of all activities, including:

-       details of any cargo damage

-       where and how the cargo was stored in the port and on the quay, ie was it stored raised from the ground on dunnage and protected from rain?

-       how cargo arrived at the berth. Did it arrive by rail/truck/ directly from the warehouse or was it shifted by a forklift truck?

-       weather: was it raining during loading/discharge? Was the steel wet?

-       whether stevedores were using the correct lifting equipment so as not to damage the cargo

-       whether stevedores used the dunnage correctly

-       the times when hatches were opened and closed, and the times of cargo operations

 

-       the condition of the cargo (take photographs).

 

10. Ship husbandry and steel cargo

Stability

The ship’s stability will need to be calculated for the proposed loading to make sure the GM is acceptable.

Large quantities of steel stowed in the bottom of a hold will cause the ship’s centre of gravity (KG) to reduce considerably, resulting in a high GM. This can make the ship ‘stiff’ and cause violent rolling in bad weather, something that can cause cargo to shift. If loading does result in an unacceptably high GM, and this cannot be corrected by ballast or moving weights, then an alternative stowage arrangement will be necessary.

 

Follow weather routing and as far as practicable try to avoid swell conditions, as these can cause heavy rolling and wavelengths equal to half the ship’s length, which in turn can initiate parametric rolling in slender ships during pitching in head seas.

Corrosion and relative humidity

Atmospheric corrosion of steel starts when the relative humidity (RH) of air reaches 40%. The corrosion rate increases slowly until the RH reaches 60% and, thereafter, it increases rapidly. Other elements will cause corrosion such as salt, funnel gases, dust or other oxidising agents. These need to be removed from the hold by cleaning before loading. Dust can be hygroscopic, trapping moisture and making corrosion worse.

To prevent atmospheric-induced corrosion, it is essential for holds to be dry and hold air to have an RH below 40%. Other forms of corrosion can be prevented by thorough hold cleaning, freshwater washing and drying.

Any source of water such as wet dunnage, or water on the tank top or in bilges, must be removed prior to closing and securing hatch covers. When at sea, carefully monitor hold humidity and ventilate when the conditions dictate. In certain conditions, dehumidifying is essential to prevent sweat. Moisture may be present in other cargo loaded in the hold. In which case, care is needed to make sure steel is not loaded adjacent to hygroscopic cargo and, if such loading is unavoidable, additional

attention should be paid to the hold’s relative humidity and ventilation.

It is the ship’s responsibility to ventilate properly or to dehumidify hold air. If steel is damaged by atmospheric corrosion, the receivers will claim damages. Making sure that cargo holds are clean and dry, and correctly following the ventilation procedure may not be sufficient to avoid atmospheric corrosion. Dehumidifying hold air will therefore also be necessary.

 

If loading in wet humid conditions cannot be avoided, avoid stowing wet steel adjacent to, or in the same compartment as, dry steel. Endorse the bills as ‘wet before shipment’. 

 

 

 

Please see attached file for reference