Guideline for Project Cargo Operations

Prof. Capt. Hermann Kaps (ret.) Bremen

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Beluga-Standard for Project Cargo Operations

Contents

Preamble ................................................................................................................................................................. 2 1. Lifting ............................................................................................................................................................. 3

1.1 General requirements .............................................................................................................................. 3 1.1.1 Definitions ....................................................................................................................................... 3 1.1.2 Information from the shipper .......................................................................................................... 3 1.1.3 Planning essentials and documentation ........................................................................................... 4

1.2 Ship's stability ......................................................................................................................................... 5 1.2.1 Minimum initial stability ................................................................................................................. 5 1.2.2 Preparation of heeling tanks ............................................................................................................ 7

1.3 Lifting Material ....................................................................................................................................... 7 1.3.1 Wire slings and grommets ............................................................................................................... 7 1.3.2 Shackles........................................................................................................................................... 8 1.3.3 Traverses ......................................................................................................................................... 8 1.3.4 Inspection and maintenance ............................................................................................................ 9

1.4 Lifting Arrangements .............................................................................................................................. 9 1.4.1 Determinacy of suspension arrangements ....................................................................................... 9 1.4.2 Single gear arrangements .............................................................................................................. 11 1.4.3 Double gear arrangements ............................................................................................................. 12 1.4.4 Tilting due to offset of centre of gravity ....................................................................................... 14 1.4.5 Stability of suspension arrangements ............................................................................................ 16

1.5 Lifting Calculations ............................................................................................................................... 17 1.5.1 Safety factors ................................................................................................................................. 17 1.5.2 Determination of required WLL-figures ....................................................................................... 18 1.5.3 Determination of sling lengths ...................................................................................................... 19 1.5.4 Forces in spreader support wires ................................................................................................... 20

2. Bedding ......................................................................................................................................................... 22 2.1 General requirements ............................................................................................................................ 22

2.1.1 Definitions ..................................................................................................................................... 22 2.1.2 Information from the shipper ........................................................................................................ 22 2.1.3 Planning essentials and documentation ......................................................................................... 23

2.2 Beam theory .......................................................................................................................................... 23 2.2.1 Shear forces and bending moments ............................................................................................... 23 2.2.2 General strength limits .................................................................................................................. 24

2.3 Loading on hatch covers and tween deck pontoons .............................................................................. 25 2.3.1 Strength limits ............................................................................................................................... 25 2.3.2 Line load........................................................................................................................................ 26 2.3.3 Straddled point load ...................................................................................................................... 26 2.3.4 Mixed loads ................................................................................................................................... 26

2.4 Beams for load spreading ...................................................................................................................... 27 2.4.1 Line support .................................................................................................................................. 28 2.4.2 Point support ................................................................................................................................. 29

3. Securing ........................................................................................................................................................ 31 3.1 Securing principles ................................................................................................................................ 31

3.1.1 Definitions ..................................................................................................................................... 31 3.1.2 Information from the shipper ........................................................................................................ 32 3.1.3 Planning essentials and documentation ......................................................................................... 32 3.1.4 External forces .............................................................................................................................. 32 3.1.5 Basic securing principles ............................................................................................................... 34

3.2 Arrangements for direct securing .......................................................................................................... 35 3.2.1 Securing against sliding ................................................................................................................ 35 3.2.2 Securing against tipping ................................................................................................................ 35 3.2.3 Direct securing by lashings only ................................................................................................... 36 3.2.4 Direct securing without securing points on the cargo ................................................................... 37 3.2.5 Direct securing by lashings and stoppers ...................................................................................... 39 3.2.6 Homogeneity of mixed securing arrangements ............................................................................. 40 3.2.7 Desirable pre-tension in lashings .................................................................................................. 41

3.3 Securing material .................................................................................................................................. 41 3.3.1 Material approved by Beluga-Shipping ......................................................................................... 41


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3.3.2 Assessment of other material ........................................................................................................ 42 3.3.3 Inspection and maintenance .......................................................................................................... 43 3.3.4 Welding standards ......................................................................................................................... 44

3.4 Determination of MSL of securing devices ........................................................................................... 44 3.4.1 Beluga standard lashings ............................................................................................................... 44 3.4.2 Securing points on cargo units ...................................................................................................... 44 3.4.3 Conventional wire rope lashings ................................................................................................... 45 3.4.4 Chain-lashings and fibre belts ....................................................................................................... 49 3.4.5 Welded stoppers ............................................................................................................................ 50 3.4.6 Timber shoring arrangements ........................................................................................................ 52

3.5 Securing calculation .............................................................................................................................. 54 3.5.1 Annex 13 Rule-of-thumb .............................................................................................................. 54 3.5.2 Annex 13 Advanced Calculation Method ..................................................................................... 55 3.5.3 Annex 13 Alternative Calculation Method .................................................................................... 55 3.5.4 Computer based calculation .......................................................................................................... 56 3.5.5 Additional tipping moment for very large cargo units .................................................................. 56

4. Stowage and securing of break bulk ............................................................................................................. 59 4.1 Pipes stowed on deck ............................................................................................................................ 59

4.1.1 Stowage and securing principles ................................................................................................... 59 4.1.2 Securing alternative 1 .................................................................................................................... 59 4.1.3 Securing alternative 2 .................................................................................................................... 60 4.1.4 Securing alternative 3 .................................................................................................................... 60 4.1.5 Longitudinal securing .................................................................................................................... 61 4.1.6 Technical details ............................................................................................................................ 61

4.2 Mixed cargo .......................................................................................................................................... 64 4.2.1 Cross-stowage ............................................................................................................................... 64 4.2.2 Side-stowage ................................................................................................................................. 66 4.2.3 Longitudinal securing .................................................................................................................... 66 4.2.4 Use of timber dunnage .................................................................................................................. 66

Preamble

The Beluga Standard for Project Cargo Operations is a controlled document of the Beluga

Group and has been developed to serve several purposes as follows:

It shall provide guidance to masters and officers of the Beluga fleet for handling, bedding

and securing of project cargo units and other non-standardised cargo.

It shall serve as background training material for junior officers and designated super-

cargo's within the Beluga Group.

It shall offer customers the opportunity to verify the performance of the Beluga Group

with regard to technical standards and the application of good seamanship in project cargo

operations.

All provisions and instructions contained in this Standard are in conformity with international

regulations and recommendations, in particular with the IMO Code of Safe Practice for Cargo

Stowage and Securing in its current edition. Units and symbols used correspond to the

Système International d'Unités (SI-units).

The Standard further complies with provisions contained in other official documents of the

Beluga Group and Beluga ships, in particular with the approved Safety Management Manual

and the Cargo Securing Manuals of the particular ships.


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1. Lifting

1.1 General requirements

1.1.1 Definitions

The following terms and definitions are used in this chapter:

cargo mass P gross mass of cargo unit, during lifting placed virtually in

the level of p metres above base

top-mass of crane(s) Q part mass of crane jib, during lifting placed virtually in the

level of q metres above the sea-going level of the jib-top

mass of suspension gear R mass of suspension gear, during lifting placed virtually in the

level of r metres above weather deck level

GMC during lifting metacentric height with (P+R+Q) in lifting level

maximum heeling moment moment of (P+R+Q) at the maximum outreach from neutral

position of crane jib

counter-ballasting moment moment of transverse ballast transfer

centre of gravity of cargo unit c.o.g., position supplied by shippers in three dimensions

centre of suspension point of connection of suspension arrangement to lifting

tackle

suspension arrangement arrangement of traverses, spreaders, slings and shackles

hanging forces vertical forces in suspension arrangement

effective forces in suspension effective forces in elements of a suspension arrangement

suspension angle angle between hanging force and effective force

stable suspension arrangement with (virtual) c.o.g below centre of suspension

unstable suspension arrangement with (virtual) c.o.g above centre of suspension

WLL working limit load as marked on lifting element

BL breaking load as declared in certificate

SF safety factor (BL/WLL)

slinging height height from bottom of cargo unit to lifting tackle

hoisting distance distance from hatch top to lifting tackle

lifting fittings fittings on cargo unit declared suitable for lifting

slinging area area on cargo unit declared suitable for placing slings

1.1.2 Information from the shipper

For safe lifting and placing a heavy cargo unit on board the following information is required

from shippers:

The mass of the unit in metric tonnes and its main dimensions including all attachments

and protrusions.


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A scale drawing of the unit showing top view, side view and front view as appropriate.

This drawing should include the position of the centre of gravity relative to the base line

and the front line in side view and relative to the centre line in top view.

The scale drawing should further contain the position and nature of lifting fittings (e.g.

chain plates, D-rings, trunnions), if supplied, or the position and size of slinging areas.

A declaration of the WLL and the BL of the lifting fittings and a note on the suitability of

the lifting fittings for securing the cargo unit with particular consideration of possible

limitations to the direction securing forces.

4.2

9 m

4.50 m 3.40 m

3.78 m 3.00 m 0.31 m

1.98 m

1.4

3 m

c.o.g.

c.o.g.

side view

top view

front view

Steam-boiler

gross mass: 78.3 t

overall dimensions: 4.50 x 3.50 x 4.29 m

c.o.g. position: see drawing

4 lifting lugs welded onto bedding beams

SWL of lifting lugs: 35 t each

8 securing points welded to securing belt

MSL of securing points: 175 kN each

2.3

4 m

Scale 1 : 100

foot print

Figure 1.1.1: Sample scale drawing

1.1.3 Planning essentials and documentation

The planning of a lift-on or lift-off procedure shall include the following aspects:

1. Selection of stowage place with regard to the crane's SWL-ranges. This task is usually

integrated into the general stowage planning and should be documented accordingly.


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2. Checking the expected metacentric height GMC of the vessel during lifting. This task

shall be accomplished by an appropriate stability calculation and documented in the cargo

operations log. Details are given in Chapter 1.2.1 below.

3. Arranging the required counter-ballasting moment with due regard to the expected maxi-

mum heeling moment. This task shall also be accomplished by an appropriate calculation

and documented in the cargo operations log. Details are given in Chapter 1.2.2 below.

4. Designing an appropriate suspension arrangement with due regard to:

outfit of the cargo unit in question with lifting fittings or slinging areas,

available lifting material of sufficient strength and dimensions,

available hoisting distance to be greater than the slinging height,

positive stability of the suspension arrangement,

distribution of forces in suspension elements and control of suspension angles.

Depending on the complexity of the individual case, a scale drawing of the suspension ar-

rangement should be prepared that allows the determination of all data necessary to check

the critical features of the arrangement. Details are given in Chapters 1.3 to 1.5 below.

The results should be documented in the cargo operations log stating as a minimum the

compliance with strength limits (actual loads less than WLL-figures),

positive stability of the suspension arrangement,

sufficient hoisting distance at all times.

1.2 Ship's stability

Loading or unloading of heavy cargo units with ship's own gear has two serious effects on the

ship's stability:

- Reduction of GM due to the lifted mass being placed virtually at the crane boom top.

- Generation of large heeling moments, which may cause the vessel to list.

With the modern heavy lift cranes used in the Beluga fleet the maximum permissible list is

restricted to 2°. Therefore it is advisable, to keep the list close to zero at all times, in order to

save an adequate margin for the operation of the ballast pumps, which are used to compensate

the heeling moments.

It is the duty of the ship's Chief Officer to check by calculation that during the lifting process

- the GMC of the vessel (corrected for free liquid surfaces in tanks) is at least 1.00 m, and

- the amount of transferable ballast is sufficient for counter-acting the heeling moment.

This is explained in more detail in the following sub-chapters.

1.2.1 Minimum initial stability

Beluga ships are operated under IMO stability criteria. The IMO Code on Intact Stability does

not contain a specific rule addressing the residual stability during heavy lift operations. This

does, however, not dispense the ship's staff from evaluating this problem in a careful manner.

In the course of pre-planning a heavy lift operation, a stability calculation must be carried out

by means of the ship's approved stability computer, which reflects the actual condition of the

ship at the time of the intended operation with regard to cargo, bunkers and ballast on board

and free surfaces in slack tanks.

The result of this calculation must be expanded to express the conditions of the lifting situa-

tion by placing the specific mass of the unit to be loaded or unloaded, together with the mass


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S

Q

R

P

s

a

q r p

d e

Figure 1.2.1: Essential data for controlling ship's stability in lifting operations


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of the suspension gear into top-level of the crane boom. This level should be estimated as the

highest position of the boom top during the operation.

In detail: The mass P of the cargo unit must be placed into the lifting level of p metres above

base. The top mass of the crane(s) Q must be shifted by q metres from the sea-going level to

the lifting level. The mass of the suspension gear R (slings, shackles, hooks, traverses) must

be shifted by r metres from the deck level to the lifting level (see Figure 1.2.1).

The result of this calculation is the metacentric height GMc for the lifting condition.

The GMc during lifting shall not be less than 1.00 m.

In case of a smaller figure additional ballast must be taken in and/or advice from the head

office should be obtained.

1.2.2 Preparation of heeling tanks

In order to keep the ship upright during all phases of the lifting operation the ship's heeling

pumps must be used. To this purpose a sufficient transfer capacity of ballast water in terms of

heeling moment must be prepared before the lifting operation can be started. The required

amount of ballast for compensating the heel is calculated as follows:

The ship is assumed upright before commencement of lifting with the crane tops in fore and

aft position at the resting distance d from the port rail. The expected outreach from the ship's

side is the distance a. Thus the total heeling lever for lifting from outboard is (d + a). The

heeling lever to the opposite side for landing the cargo unit inboard is e, which depends on the

intended stowage position (see Figure 1.2.1).

The maximum heeling moment is (d + a) (P + Q + R) or e (P + Q + R), whichever is

greater. A sufficient capacity of ballast water S with a transverse lever s is required to obtain

an equal counter-ballasting moment. This lever should be taken as an average value for suit-

able side tanks of the particular ship. The necessary amount of water is:

s

)QRP()ad(S

[t] or

s

)QRP(eS

[t]

This amount of water, plus a margin of 10 %, should be available for pumping into either di-

rection.

1.3 Lifting Material

Project carriers in the Beluga fleet are equipped with a standard set of wire rope slings and

grommets, shackles and traverses for lifting heavy cargo units.

1.3.1 Wire slings and grommets

The details of wire rope slings and grommets are addressed to in the particular inventory list

on board.


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working length

grommet diameter red coloured splice

working length

sling diameter eye length

Figure 1.3.1: Wire rope lifting grommet and sling

1.3.2 Shackles

The details of shackles are addressed to in the particular inventory list on board.

Figure 1.3.2: Lifting shackle

1.3.3 Traverses

The equipment of product carriers in the Beluga fleet with traverses depends largely on the

current engagement with the transport of heavy lifts. The following overview shows the avail-

able items and their properties.

Traverses of SWL = 250 t are available in different lengths.

length 3.0 m 4.0 m 5.0 m 6.0 m 7.0 m 8.0 m 9.0 m

own mass 1.10 t 1.27 t 1.42 t 1.58 t 1.73 t 189 t 2.00 t

Length

Figure 1.3.3: Traverse of SWL = 250 t

For handling heavy units of relatively small size with two cranes a traverse is used, which

accommodates the usual lifting double hooks on both ends and provides trunnions on both

sides for attaching slings or grommets (Figure 1.3.4).


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18.000 m

1.5 m 1.5 m 3.0 m

250 t SWL = 460 t 250 t

Figure 1.3.4: Traverse of SWL = 460 t

1.3.4 Inspection and maintenance

All lifting equipment must be carefully inspected before and after each use. Wire slings and

wire grommets shall be preserved with wire rope grease and threads of shackle bolts shall be

greased at suitable intervals to avoid corrosion.

Wire ropes must be discarded if at a length of 8 times the wire diameter more than 10 % of

the single wires are visibly broken. Shackles must be discarded if the diameter of jokes or

bolts is locally reduced by 10 % from abrasion or if visibly deformed. Rejected lifting mate-

rial must be disposed for transport to a scrap yard. The receipt of such disposal must be kept

on board and the company informed accordingly. Disposal of such material over board at sea

is not permitted by Beluga Shipping.

Any employment of lifting equipment for loading or unloading heavy cargo must be entered

into the specific journal, as well as any activity regarding maintenance or discarding of

equipment.

1.4 Lifting Arrangements

1.4.1 Determinacy of suspension arrangements

Arrangements with two lifting points are quite often used for longish units (Figure 1.4.1).

Figure 1.4.1: Suspension arrangement with two lifting points

The distribution of the load between the two lifting points depends on their position in relation

to the c.o.g., following the general rule that the hanging forces are inversely proportional to

their distances to the c.o.g. (Figure 1.4.2). The forces are calculated as follows:

21

21ee

gPeF

and

21

12ee

gPeF


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e2 e1

hanging force F1 hanging force F2

weight Pg

Figure 1.4.2: Hanging forces in an asymmetric two point suspension

Arrangements with three lifting points are scarcely used. The precise determination of the

hanging forces may require a lengthy calculation.

Suspension arrangements with more than three lifting points are statically indeterminate. The

hanging forces cannot be precisely determined but only estimated with reasonable accuracy

(see chapter 1.5). It is of utmost importance that the length of slings complies with the geome-

try of the suspension arrangement.

Figure 1.4.3 shows a suspension arrangement with four slings shackled onto four adequate

eye plates on the unit. Two of the slings appear to be a bit too long resulting in overloading

the two other slings.

This deficiency may be avoided by an arrangement shown in Figure 1.4.4, where two of the

slings have been replaced by one sling of double the length, run as a "loop over the hook". In

this way the statically indeterminate four-point suspension has been converted into a statically

determinable three-point suspension.

Such "loop over the hook" slings should not be used on both ends of the cargo unit in order to

avoid the risk of tilting.

Figure 1.4.3: Four slings with obvi-

ous imbalance of load distribution

Figure 1.4.4: Even load distribution with one "loop over the

hook" sling

Lifting with two "loop under the bottom" slings will usually provide an equal distribution of

the load to all four parts (see Figure 1.4.5). The risk of tilting is minimal due to the friction of

the slings around the bottom of the cargo unit.


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Figure 1.4.5: Lifting with two loops under the bottom

1.4.2 Single gear arrangements

Single gear arrangements use only one crane for lifting. The c.o.g. of the unit will be verti-

cally under the lifting tackle.

Figure 1.4.6: Single gear arrangement with transverse traverses

The slings in Figure 1.4.6 are connected to solid trunnions fitted to the base frame of the unit.

Also this suspension arrangement is statically indeterminate and therefore needs four slings

having the same length.

If the slings run as loops under the bottom of the unit it is important to avoid slipping of the

slings to the centre of the unit. The favourite option is to use a longitudinal traverse that keeps

the slings vertical (Figure 1.4.7).


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Figure 1.4.7: Single gear arrangement with longitudinal traverse

Another option, frequently used with light cargo units, are running straps or slings. But it is

dangerous to use running slings for heavy lift units. The wire will be cut in the eye during

tightening. Therefore running slings are not permitted for heavy lifts in Beluga Shipping.

Figure 1.4.8: Never use running slings for heavy lift units

1.4.3 Double gear arrangements

Double gear arrangements are used when two cranes are needed for lifting the cargo unit

safely. The principles of determinacy of hanging forces are the same as with single gear ar-

rangements. A traverse for connecting both lifting tackles is generally not necessary if the

cargo unit is long (Figure 1.4.9).

If the cargo unit is small a traverse should be used (Figure 1.4.10). This avoids any contact

between the crane tops and may be moreover necessary to reduce the outreach of the crane

booms to utilise their full lifting capacity.


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Figure 1.4.9: Double gear arrangement without longitudinal traverse

Figure 1.4.10: Double gear arrangement with longitudinal traverse

In case of an asymmetric double gear suspension arrangement the hanging forces in slings and

in lifting tackles must be calculated using the principle of "inverse proportionality". The load

in the slings depends on their distances to the centre of gravity of the unit e1 and e2 (see Figure

1.4.11).

gPee

eL

21

2

1

and gPee

eL

21

1

2

The load in the lifting tackles must also take the mass of the traverse into account.

2

gTgP

ff

fD

21

2

1

and

2

gTgP

ff

fD

21

1

2


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Figure 1.4.11: Asymmetric double gear suspension arrangement

1.4.4 Tilting due to offset of centre of gravity

The layout of a lifting arrangement should be generally designed under the assumption of a

centre of gravity of the particular cargo unit that is in or very close to its geometrical centre

unless informed otherwise by the shipper. Any unexpected eccentric position of the centre of

gravity or transverse deviation from the advised position will tilt the suspended cargo unit and

distribute the loads in the suspension gear unevenly.

h

centre of suspension

centre of gravity

e

Figure 1.4.12: Tilting of a suspended cargo

unit due to eccentricity of c.o.g.


F1

F2

P g

centre of gravity

Figure 1.4.13: Uneven distribution of forces

in slings

The magnitude of a tilt angle depends on the eccentricity e of the c.o.g. and on the vertical

distance h of the c.o.g. from the suspension centre (Figure 1.4.12). The hanging forces are

greater on the low side of the tilted unit (Figure 1.4.13).


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Another disadvantage of tilting may be the difficulty of placing the unit at the intended stow-

age position. This problem can be solved by elongating the sling(s) on the high side, e.g. with

by inserted shackles. However, this does not equalise the different loads in the slings, as dem-

onstrated by Figure 1.4.14.


F1 F2

1 2

centre of gravity

P g

Figure 1.4.14: Suspension rectified by adapting the length of slings.

A suspension arrangement is more liable to tilting, even with a small eccentricity of the c.o.g.,

if the slings are fastened to traverses above as shown in Figure 1.4.15.

Figure 1.4.15: Suspension arrangement with traverses, slings fastened below c.o.g.


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An effective "virtual" position of the c.o.g. reduces the distance to the centre of suspension

(Figure 1.4.16). The cargo unit may touch the vertical slings causing damage to a sensitive

surface and produce mechanical strain to the sling (Figure 1.4.17).


virtual position of unit

excentric position of c.o.g.


excentric position of c.o.g.

Figure 1.4.16: Virtual position of a cargo unit

suspended under a traverse

Figure 1.4.17: Actual suspension with eccen-

tric c.o.g

1.4.5 Stability of suspension arrangements

If the centre of gravity of the cargo unit c.o.g. is positioned below the centre of suspension

c.o.s. the arrangement is stable, unless a tilting angle due to temporary external influences like

wind or swell is less than the suspension angle of slings. Figure 1.4.18 shows three stable ar-

rangements.

absolutely stable sufficiently stable poorly stable

c.o.g. c.o.g. c.o.g.

c.o.s. c.o.s. c.o.s.

Figure 1.4.18: Stable suspension arrangements


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If the c.o.g. is positioned above the c.o.s. the arrangement is unstable and will capsize at the

least disturbing influence (Figure 1.4.19).

c.o.s. c.o.s.

c.o.g. c.o.g.

absolutely unstable

Figure 1.4.19: Unstable suspension

In suspension arrangements with traverses the virtual position of the c.o.g. is always above the

actual position by the length of the vertical slings (see also Figures 1.4.16 and 1.4.17). Such

arrangements become unstable if the virtual c.o.g. is located above the c.o.s. of the arrange-

ment.

absolutely stable absolutely unstable poorly stable

c.o.g.

c.o.s.

virtual c.o.g.

c.o.g.

c.o.s.

virtual c.o.g.

c.o.g.

c.o.s.

virtual c.o.g.

Figure 1.4.20: Stable and unstable arrangements with traverse

1.5 Lifting Calculations

In the course of planning the suspension gear for lifting of heavy cargo units, the required

WLL-figures of slings, shackles and traverses must be determined by calculation with due

regard to safety factors adopted by Beluga Shipping.

In cases with asymmetric suspension it may additionally become necessary to precisely de-

termine the required length of slings.

1.5.1 Safety factors

The Working Limit Load (WLL) of a suspension element is a figure that indicates the permis-

sible load (mass) given in metric tons to be lifted vertically by this particular element. The

specification of WLL generally incorporates a safety factor (SF) against the nominal breaking

load (BL) of that element.


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The nominal breaking strength of lifting material is increasingly supplied with kN-marking by

manufacturers and chandlers. BL-figures in tonnes may be obtained by dividing the kN-

figures by the g-factor of 9.81 m/s2.

The relation between BL and WLL reads: kNor]t[SF

BLWLL

Safety factors for suspension elements in heavy lift operations on ships are not governed by

public legislation. Beluga Shipping uses the following safety factors for suspension material:

Material Safety factor

Shackles 6

Wire grommets 5

Wire slings 4

Polyester grommets 7

Steel belts 6.7

The WLL of traverses is directly declared and documented by the manufacturer.

1.5.2 Determination of required WLL-figures

The required WLL-values in a suspension arrangement shall be determined in three steps:

- Evaluation of hanging forces

- Calculation of effective forces in shackles and slings

- Selection of required WLL

In case of a symmetrical suspension arrangement the hanging forces may simply be obtained

by dividing the weight of the unit by the number of slings. In asymmetrical arrangements the

hanging forces must be calculated as shown in chapter 1.4.1, using the principle of inverse

proportionality.

The effective forces in shackles and slings depend on the suspension angle following the

equation:

]kN[cos

FS

F S

Figure 1.5.1: Suspension angle


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1.5.3 Determination of sling lengths

A precise determination of sling length is necessary if a unit shall be lifted with an asymme-

trical suspension arrangement. This task requires a fairly exact drawing of the unit with top

view and side views containing all necessary details of lifting appliances, like trunnions or eye

plates, and the position of the centre of gravity of the unit.

The length of slings in a suspension arrangement should be determined in three steps:

Decision on "slinging height"

Determination of the geometrical gross length of slings

Calculation of the effective net length of sling by considering shackles, bends etc.

Figure 1.5.2: Slinging height s

Hoisting distance h

Hatch coaming or hatch top

Figure 1.5.3: Hoisting distance h


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The slinging height (Figure 1.5.2) is the total distance from the bottom of the unit up to the

bolt of the crane hook. This distance must not be greater than the available hoisting distance

(Figure 1.5.3), which is usually no problem with modern crane equipment.

The geometrical gross length of a sling is the spatial distance from the distinguished lifting

appliance of the unit to the upper side of the hook or shackle or traverse trunnion.

The effective net length of each sling is obtained by deducting the length of shackles with due

consideration of the radii of shackle bolt and shackle body.

1.5.4 Forces in spreader support wires

Occasionally cargo units are lifted with spreaders instead of traverses. These spreaders have

the beneficial effect that the load in the slings is not increased by the slinging angle . How-

ever, the spreaders themselves must be supported by extra slings which have to take the addi-

tional load created by the suspension angle . Figure 1.5.4 shows the different loads in the

arrangements with traverse and spreader.

cos2

TW

W

W

T

W/2

W+T

2cos

W

S

W/2

W/2 spreader

support wires

Figure 1.5.4: Lifting arrangement with traverse (left) and spreader (right)

/2

W/2

W/2

W/2 sin tan/2

W/2 sin

Figure 1.5.5: Transverse and vertical forces (red) to the spreader boom


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The load LS in the spreader support wires results mainly from the vertical component of the

resultant of the forces in the sling, but must also take account of the weight S of the spreader

itself. For each support wire, with W and S given in t, the load LS is:

cos2

S

2tantan

2

WLS [t]

The support wires have to carry a lot more than only the weight of the spreader and must be

dimensioned accordingly.


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2. Bedding

2.1 General requirements

2.1.1 Definitions

The following terms and definitions are used in this chapter:

beam general term for a lengthy piece of square timber or steel H-

profile that is used for transferring or spreading a load to the

stowage area

girder steel profile in the ship's structure, in this chapter usually

meant as a stiffener under the plating of the stowage area

shear force (SF) internal force in a beam that is subjected to bending; shear

forces are directed perpendicular to the beam

bending moment (BM) internal moment in a beam that is subjected to bending; the

bending moment causes tension and pressure stresses in the

beam

mass (m) invariable property of a defined object or substance; meas-

ured in kilogram [kg] or (metric) tonne [t]

weight (W) force that a mass produces at a suspension or on a bedding

surface caused by the gravity acceleration: W = m g [kN]

tensile stress () force /area with the force perpendicular to the area: = F / A

[kN/cm2]

shear stress () force /area with the force parallel to the area: = F / A

[kN/cm2]

section modulus (SM) property of a beam that characterises its resistance against

bending, measured in [cm3]

uniform deck load (UDL) design parameter for the strength layout of a deck, hatch

cover or tank top; usually given as UDLlim in [t/m2] in ship's

plans or specifications

line load cargo that is distributed evenly over a certain proportion of a

stowage area that acts as a beam within the ship

point load cargo that is placed only on certain small areas of a stowage

area that acts as a beam within the ship

line support a beam used for load distribution that is resting over its full

length on the stowage area

point support a beam used for load distribution that is resting only at its

ends and thus bridging the stowage area


For safe bedding a heavy cargo unit on board and carrying it without damage to itself and to

the ship's structure, also in heavy weather, the following information in addition to those

listed under chapter 1.1.2 is required from shippers:


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The position and dimensions of the footprint areas of the unit.

Information on adequate bedding areas if the unit has no specific footprint areas.


The bedding of heavy cargo units in ships requires proper pre-planning and the consideration

of the structural strength of the stowage area. A bedding plan shall be prepared showing the

necessary beams for load distribution. Appropriate calculations shall be made to assure that

the ship's structure is not overloaded with due regard to the applicable uniform deck load

UDLlim and additional strength information contained in the ship's capacity plan,

any beams used for load distribution or load transfer to ship's structures are sufficient in

number and strength with regard to their section modulus.

The bedding plan and the appropriate calculation results shall be filed in the cargo operations

log on board the ship.

2.2 Beam theory

A precise determination and evaluation of measures to avoid over-stressing of particular ship's

structures is advisable in general. However, a more easy approach on the basis of the simple

beam theory will also present suitable results in most cases.

The beam theory would apply to the loading of weather deck hatch covers and tween deck

pontoons as well as to the evaluation of timber or steel beams used for spreading concentrated

loads. Therefore the beam theory, based on a loaded beam resting on its ends, is presented.

2.2.1 Shear forces and bending moments

Figure 2.2.1 shows a beam of the length r, which rests on its ends. It is loaded by a mass m

with a length s, placed symmetrically on the beam. The weight of the mass is W = m g. The

supporting forces FA and FB at both ends of the beam are mg/2. The own weight of the beam

is ignored in this advisement.

mg/s

mg/2 r

mg/2 s

Figure: 2.2.1: Loaded beam resting on its ends

Shear forces at both ends of the beam: SFmax = mg/2 [kN]

Bending moment at the middle of the beam: sr28

gmBMmax

[kNm]

It should be noted, that s = r for a homogeneous load and s = 0 for a pin-point load.

Figure 2.2.2 shows a similar beam loaded asymmetrically. This loading the beam off centre

by an offset e reduces the BMmax. Also the shear forces FA and FB are not equal:

r

e21

2

gmSFA

r

e21

2

gmSFB


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FB r

FA

mg/s

s

e

Figure 2.2.2: Beam loaded off centre

2

2

maxr

e41)sr2(

8

gmBM [kNm]

The location of BMmax is no longer at the centre of the beam but at (r/2 – e + es/r), located

between the centre of the load and the centre of the beam.

A cargo unit that is internally stiff so that it "bridges" the panel or pontoon partially, will also

reduce the bending moment in the pontoon as shown in Figure 2.2.3.

weight = mg

mg/2 r

mg/2 s

Figure 2.2.3: Straddled load on a beam

s2r28

gmBMmax

[kNm]

2.2.2 General strength limits

Shear forces (SF) and bending moments (BM) induce internal stresses in the beam, which

should not exceed certain limits. These are defined with reasonable safety margins.

The shear stress in a beam is calculated in simplified manner by:

2cm

kN

A

SF with A = cross-sectional area at the stress location

The permissible shear stress for mild steel is in the range of 10 kN/cm2.

The bending stress in a beam is calculated by:

2cm

kN

SM

BM with SM = section modulus at the stress location

The permissible bending stress for mild steel is in the range of 15 kN/cm2. For conifer tim-

ber it is about 1 kN/cm2.

The section modulus is a term for denoting the bending resistance of a beam. For simple

square timber beams the section modulus is calculated by:

32

cm6

hbSM


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b

h

Figure 2.2.4: Steel beam and timber beam

The section modulus for steel beams must be obtained from manufacturer's tables. The fol-

lowing data for steel beams should be used as a reference only.

Dimensions b x h [cm] 12 x 12 14 x 14 16 x 16 18 x 18 20 x 20 26 x 26 30 x 30

Section modulus [cm3] 144 216 311 426 570 1150 1680

However, if the beam under consideration is a complete tween deck pontoon or a weather

deck hatch cover, the strength limits depend on additional structural features and are not easy

to determine. Usually, these pontoons or covers are designed to withstand a homogeneous

load UDLlim1 that is agreed upon in the building contract and advised in the capacity plan of

the vessel.

The strength limits in these cases may be directly referred to limiting shear forces and limiting

bending moments, which are equal to those of the design condition. These would include dy-

namic effects to the ship in heavy seaway.

kN2

gtrUDLSF lim

lim

mkN

8

gtrUDLBM

2

limlim

UDL

r

t

Figure 2.2.5: Homogeneously loaded tween deck pontoon

Generally, the limiting criterion for the design of a tween deck pontoon is the bending mo-

ment and the actual SFlim may be greater than given by the above formula. This should be

ascertained for the individual case by asking the designer or builder.

2.3 Loading on hatch covers and tween deck pontoons

2.3.1 Strength limits

Weather deck hatch covers

The weather deck hatch covers have been designed for a permissible UDL in the range of 3 to

4 t/m2. Applicable figures are given in the ships' capacity plans. Using their dimensions width

by length the permissible shear forces and bending moments per panel may be calculated.

Higher loads, equal to the sum of partial stack loads across the hatch cover, can be taken in

the way of the container sockets. In addition, there may be certain areas (paint marked) at the

hatch coamings or at the seams between hatch covers, where specified point loads can be

1 UDLlim = permissible uniform deck load [t/m

2]


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taken, and narrow stripes of 20 cm width (paint marked) in the way of secondary girders,

where specified line loads can be taken. This is shown in a specific plan on board the vessels.

Tween deck pontoons

The tween deck pontoons have been designed for a permissible UDL in the range of 3.0 t/m2.

Applicable figures are given in the ships' capacity plans. Using their dimensions width by

length the permissible shear forces and bending moments per pontoon may be calculated.

The given figures of SFlim may be exceeded by 20% due to margins kept for local strength.

2.3.2 Line load

A cargo unit with a flexibility that is equal to or greater than the flexibility of the hatch cover

or pontoon must be supported at short distances and shall hence be considered as a "line load"

on that hatch cover or pontoon. The maximum bending moment exerted to the panel or pon-

toon must be calculated as shown in the previous sub-chapter by:

sr28

gmBMmax

[kNm]

If the limiting BM-figure is exceeded, the loaded length of that hatch cover or pontoon must

be extended by the use of load spreading beams. Any unused space in the loaded length must

not be allocated for other cargo.

2.3.3 Straddled point load

A cargo unit with a sufficient internal stiffness, in most cases recognisable by the position of

its footprints, may be loaded in a way that it bridges or straddles partially the centre of the

panel or pontoon and thereby reduces the bending moment. The maximum bending moment

exerted to the panel or pontoon may be calculated as shown in the previous sub-chapter by:

s2r28

gmBMmax

[kNm]

2.3.4 Mixed loads

If more than one cargo unit shall be loaded onto a distinguished section of weather deck hatch

covers or tween deck pontoons, the maximum bending moment cannot be calculated by one

of the simple formulae above, but must be obtained by computing the area under the shear

force curve from the left side to the intersection with the zero-line. This is demonstrated in the

following situation.

Figure 2.3.1: Example with mixed loads on a weather deck panel


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0.4

21

55.5

3.6

14

29.6

1.5

70

3.6

2.6

27

2.0

2.1

15

9.7

19

64.7

FA

FB

7.0

BMmax = blue area [kNm]

Figure 2.3.2: Shear force curve for mixed loads

2.4 Beams for load spreading

Whenever the enveloping area of the footprint of a heavy cargo unit is smaller than the ratio

mass / UDLlim, beams may be required in order to spread the load onto a greater number of

structural girders of the stowage place. Two situations may be distinguished:

Beams are placed flat onto the stowage place and thus supported along their entire length.

This is referred to as line support of the beams.

Beams are placed with their ends onto strong regions of the stowage place and thus bridge

a weaker region. This is a point support of the beams.

Figure 2.3.3: Longitudinal timber beams for load spreading

Figure 2.3.4: Longitudinal steel beams for load spreading


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2.4.1 Line support

The number of beams and their strength must be sufficient and should be checked by calcula-

tion. The strength of the beam is characterised by the section modulus (see Chapter 2.2.2).

With m = mass of unit in tonnes; g = gravity acceleration 9.81 m/s2; SM = section modulus of

beams; r = length of beams in cm; s = loaded length of beams in cm, the required number of

beams may be obtained by the following formulae:

Number of required beams n = SM8

)sr(gm

for timber beams.


)sr(gm

for steel beams.

r

m

s

Figure 2.3.5: Beams with line support

The effective length of beams is limited due to their tendency to bending their ends up. The

following list indicates, as a rules of thumb, the maximum effective length r of beams depend-

ing on their loaded length s.

Timber beams 10 x 10 cm: rmax = (1.2 s + 0.8) m, but not more than (s + 1.0) m



Steel beams 12 x 12 cm: rmax = (1.2 s + 3.0) m, but not more than (s + 4.0) m






If the cargo unit is loaded on narrow stripes of footprint (Figure 2.3.6), the same formulae are

applicable. However, the small value for s may be replaced by Zero.

r

m

s

Figure 2.3.6: Beams with line support and point load from top


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Hence the formulae will read:


rgm

for timber beams.


rgm

for steel beams.

It should be noted in this case that the number of beams is as in the situation of Figure 2.3.5

but the beams have only half the length or less. That is of considerable commercial advantage.

2.4.2 Point support

Again, the number of beams and their strength must be sufficient and should be checked by

calculation. The applicable formulae show the relation to those used for hatch covers and pon-

toons. With m = mass of unit in tonnes; g = gravity acceleration 9.81 m/s2; SM = section

modulus of beams; r = length of beams in cm; s = loaded length of beams in cm, the required

number of beams may be obtained by the following formulae:


)sr2(gm

for timber beams.


)sr2(gm

for steel beams.

This situation is typical for bridging the weak area between container sockets with steel

beams on weather deck hatch covers. Timber beams are generally not suitable for this pur-

pose.

r

m

s

Figure 2.3.7: Beams with even load from top and point support at their ends

If the load m is not placed at the middle of the beam, the "offset" e may be taken into account

accordingly (Figure 2.3.8).

Number of required beams n =

2

2

r

e41

SM120

)sr2(gm for steel beams.

Figure 2.3.8: Beams loaded with offset e


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If such point supported beams are loaded by a cargo unit which itself bridges the middle of

the beams while resting on footprints crossing the beams, the required number of beams may

be considerably reduced (Figure 2.3.9).


)s2r2(gm

for timber beams.


)s2r2(gm

for steel beams.

r

m

s

Figure 2.3.9: Beams with straddled load and point support


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3. Securing

3.1 Securing principles

3.1.1 Definitions

The following terms and definitions are used in this chapter. They are mainly based on the

IMO CSS-Code.

Kilo Newton (kN) suitable unit of force under the SI-System for securing con-

siderations; it replaces the traditional tonne or kilogram,

which should be used for the mass only; the force of 1 kN

corresponds to about 0.1 tonne or 100 kg, taken as weight or

force in the old fashion

securing element single piece of securing equipment like a deck ring, shackle,

turn buckle, chain, wire, wire clip or securing point on the

cargo unit

securing device suitable combination of securing elements forming a lashing,

a shore or a welded stopper

homogeneous securing device consists of elements having the same values of MSL

securing arrangement a suitable composition of securing devices

homogeneous securing ar-

rangement

consists of securing devices of suitably adapted strength and

geometrical configuration to achieve, that in case of an ex-

treme external load all the devices carry their share and are

not loaded beyond their MSL

breaking load (BL)

or breaking strength

nominal force at which a securing element will break; in-

formation to be supplied by manufacturer or chandler; for

some securing materials BL is available by rules of thumb

Annex 13 method calculation method for evaluating a securing arrangement

supplied in the Annex 13 to the IMO CSS-Code; latest edi-

tion from 2003, MSC/Circ. 1026

maximum securing load

(MSL)

maximum acceptable force in a securing element or securing

device; the Annex 13 shows a table with MSL as percentage

of BL for different materials

calculation strength (CS) MSL reduced by a factor of safety; figures of CS for secur-

ing devices are only used in balance calculations according

to the Annex 13

CS = MSL / 1.5 for the standard method

CS = MSL / 1.35 for the alternative method

cross-stowage stowage pattern where the cargo is tightly stuffed between

and supported by the ship's sides or other fixed structures

like longitudinal bulkheads; minimal securing effort neces-

sary in general; securing against longitudinal forces required

in fore or aft holds, because friction may be reduced due to

temporary vertical forces; compacting of surface of cargo

may be required if units may jump out


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side-stowage support against transverse forces is given by fixed ship's

structure from one side only; there is a need for transverse

securing to the other side and also longitudinal securing

single stowage stowage pattern applicable to single cargo units stowed on

deck or in the hold; unit needs securing from all sides


For securing a heavy cargo unit on board against movement and breaking loose in heavy

weather, the following information in addition to those listed under chapters 1.1.2 and 2.1.2 is

required from shippers:

The position and MSL of securing points on the unit.

Limitations of the direction of forces to securing points on the unit.

Alternatively, information on securing areas where loop lashings may be attached.

Sensitivity of the unit against racking deformation.


The securing of heavy cargo units in ships requires proper pre-planning for the prevention of

sliding and tipping in transverse and longitudinal direction. With units of weak construction

also racking should be prevented. A securing plan shall be prepared indicating the lashings,

shores and welded stoppers as appropriate. The plan shall be supplemented by a list contain-

ing the MSL figures for each securing device, the lashing angles and additional information

necessary in order to assess the securing arrangement by means of the Annex 13 method.

An appropriate calculation shall be made using the Annex 13 method, either by manual calcu-

lation or using a recognised computer program2, in order to verify sufficient protection against

transverse and longitudinal sliding,

transverse tipping and also longitudinal tipping if applicable.

The securing plan and the calculation sheets shall be filed in the cargo operations log on board

the ship.

3.1.4 External forces

Forces acting on cargo units on sea-going vessels are resulting from three main sources:

Gravity forces with their components in the transverse and longitudinal direction of the

ship's co-ordinate system due to rolling or pitching.

Inertia forces on cargo units due to accelerations of the ship, which is the physical refer-

ence system for the cargo.

Impact forces resulting from the impact of wind or heavy water spray on cargo units

stowed on deck.

Forces from the above sources act as a combined vector within a three dimensional co-

ordinate system of the ship. This vector varies permanently. For ease of comprehension and

valuation, the three components of this vector are considered separately. The three compo-

nents are:

Fx = longitudinal force,

Fy = transverse force,

Fz = vertical force.

2 e.g. LashCon by DNV


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Although ships tend either to roll heavily or to pitch heavily, there may be simultaneous mo-

tions in both ways. Therefore, peak values of forces in the transverse direction may appear in

combination with up to 60% of peak values in the longitudinal and the vertical direction and

vice versa. However, peak values in the longitudinal direction and in the vertical direction

may appear together with 100% each, because of their common sources from pitching and

heaving motions of the ship.

Figure 3.1.1: Rolling and pitching motions of ships

The magnitude of forces to be expected during a voyage depends on a number of circum-

stances and parameters. These are explained as follows:

Weather, wind and sea conditions cannot easily be predicted over a period of more than a

couple of days although some certainty may be given through the knowledge of typical condi-

tions in distinguished areas and during certain seasons of the year.

Duration of the voyage has a general influence on the probability of meeting unfavourable

weather and sea conditions. In a short voyage this risk is smaller and can be better controlled

by observing the weather forecast.

Behaviour of the ship can be classified by size of the ship, her stability and her speed.

Large ships do not find a sea condition producing violent motions as often as do small

ships. In large ships there is a reduced risk of severe forces to the cargo.

Ships with high initial stability and shorter periods of roll meet "resonant" wave encoun-

ters and large roll amplitudes with greater probability than do ships with a low initial sta-

bility. In addition, "stiff" vessels produce higher transverse forces through their shorter

periods of roll and higher angular accelerations.

Ships running at high speed will more easily take heavy shocks from waves than will do

slow ships. Thus, forces increase with speed in general.

Location of stowage of a particular cargo unit has a significant influence on the magnitude of

forces expected during the voyage.

Longitudinal forces increase from lower hold to stowage high on deck.

Transverse forces increase from lower hold to stowage high on deck and from a position

at about 45% of the length towards the forward and aft end of the ship.

Vertical forces (in addition to the omnipresent gravity component) increase from a posi-

tion at about 45% of the length towards the forward and aft end of the ship.

Stowage positions on the weather deck or hatch top are subject to impact forces by wind

and sea sloshing.

Mass of the cargo unit gives a proportional effect to gravity forces and to inertial forces,

following Newton’s Law.

Dimensions of the cargo unit have an influence to impact forces which are proportional to

the affected area of the unit. This will of course only apply to deck cargo.


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0

.8 g

0

.4 g

0.3 g

0.1 g 0

.6 g

0.5 g

0.8 g

0.6 g

Figure 3.1.2: Approximate accelerations to the ship

3.1.5 Basic securing principles

Practical securing of cargo may be categorised as follows:

Direct securing means to apply lashings, shores or locks in order to transfer external forces

directly from the cargo to the ship's structure. This is achieved most efficiently if the direction

of the lashing, shore or lock is as close as possible to the direction of the force which is to be

counter-acted. That means, a lashing intended to prevent transverse sliding should run in the

transverse direction at a low angle or parallel to the deck.

Friction securing means to apply and pre-tension lashings in a way to increase the vertical

force to the stowage area. The appropriate lashing will therefore be set in a close to vertical

direction. This principle is less effective than direct securing by two reasons. The first reason

is that the helpful additional friction force is equal to the pre-tension in the lashing multiplied

by the friction coefficient of 0.3 with timber. Thus only 30% of the lashing force is used. The

second reason is that the force in the lashing will only depend on its pre-tension effected by a

tightening device. This pre-tension will not last very long due to settling effects.

But there is also one advantage. Friction securing, if effective, acts into any direction, i.e. to

fore and aft, to port and to starboard. The main reason for applying friction securing may be

limited space on board or lack of suitable securing points. A typical example for nearly pure

friction securing is found with timber deck cargo stowed from side to side. Also cargo on road

vehicles and roll trailers is quite often secured in this way, but this is usually insufficient for

sea-transport.

Compacting means to apply securing material in order to compact a bulk of cargo units.

There is no direct or indirect transfer of forces to the ship's structure. Thus compacting must

necessarily always be combined with a reliable stowage pattern like cross-stowage. A typical

example for compacting is the securing of steel coils in lower holds.

Heavy project cargo units and similar sensitive cargo must be secured by direct securing only.

If a direct securing arrangement also implies friction increasing and compacting, this is a wel-

come side effect.


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3.2 Arrangements for direct securing

3.2.1 Securing against sliding

Cargo units must be secured against transverse and longitudinal sliding in the first place.

Good friction between the foot print of a cargo unit and the stowage area is the most eco-

nomic way of providing a primary resistance against sliding in all directions. Friction must be

improved by placing timber or rubber mats under the cargo unit. If steel beams are used for

bedding, timber boards or rubber mats must be placed both between cargo unit and steel

beams as well as between steel beams and the stowage area, unless the beams are effectively

secured to the stowage area by welding or shoring.

As a general first estimation, the overall securing effort for a particular cargo unit should be

distributed into 40% both to port and to starboard, and 10% both to fore and aft. Taking the

rule of thumb in the Annex 13 to the CSS-Code into account and the usual size of vessels op-

erated by Beluga Shipping, the above estimation may be expressed in terms of MSL as fol-

lows:

MSL to starboard = 70% of the weight of the unit,

MSL to port side = 70% of the weight of the unit,

MSL to forward = 18% of the weight of the unit,

MSL to aft = 18% of the weight of the unit.

weight W

MSL = 18% W to fore

MSL = 18% W to aft

MSL = 70% W to stbd

MSL = 70% W to port

Fig. 3.2.1: Distribution of lashing strength

Transverse securing must be up-graded against the above estimation, if the ship is considered

as "stiff" with a rolling period of less than 13 seconds. Longitudinal securing must be up-

graded against the above estimation for stowage locations on deck forward of 0.7 Lpp. Longi-

tudinal sliding in the lower hold and tween deck between 0.3 Lpp and 0.7 Lpp will generally

be prevented by the friction of steel on timber alone. In any case of doubt, the securing ar-

rangement must be assessed by the advanced calculation method and upgraded accordingly.

3.2.2 Securing against tipping

Securing against transverse tipping must be considered in general, if the height of the centre

of gravity of a unit above the deck is greater than 60% of the width of the transverse base of

the unit.


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h

w

stbd port

c.o.g.

Figure 3.2.2: Risk of transverse tipping with h > 0.6 w

In the case of an asymmetrical arrangements of the centre of gravity and/or the tipping axis a

thorough analysis of the necessary tipping resistance of the securing arrangement must be

carried out in accordance with the advanced calculation method.

a

stbd port

b

tipping axis

c.o.g.

Figure 3.2.3: Analysis of tipping with asymmetrical conditions

Securing against longitudinal tipping will be limited to rare situations where the height of the

centre of gravity of a unit above the deck is greater than 120% of the length of the longitudi-

nal base of the unit.

h

l

fwd aft c.o.g.

Figure 3.2.4: Risk of longitudinal tipping with h > 1.2 l

Securing against tipping may be effected by the same lashings intended for the prevention of

sliding, provided the lashings act with a suitable lever with regard to the relevant tipping axis.

3.2.3 Direct securing by lashings only

Vertical lashing angles should not exceed 60° for the prevention of sliding. Horizontal lash-

ing angles , i.e. deviation of transverse lashings from the transverse direction or the deviation

of longitudinal lashings from the longitudinal direction, should not exceed 30°.

In an ideal case the cargo unit is equipped with a sufficient number of securing points at about

half the height of the unit and of sufficient strength. If all lashings have permissible deviations

from the transverse direction, equally to fore and aft, no extra lashings against longitudinal

securing are required. If all lashings have sufficient levers c to the appropriate tipping axis, no

extra lashings are required against transverse tipping.


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f wd

aft

tipping axis

levers c

Figure 3.2.5: Ideal securing arrangement against transverse and longitudinal sliding

and transverse tipping

3.2.4 Direct securing without securing points on the cargo

Quite often heavy cargo units are delivered for shipment without having dedicated securing

points. In those cases loops of lashings have to be put around the whole body of the unit in a

suitable way on order to prevent sliding and tipping. Pure vertical loops, although preferably

used in road transport, are insufficient for sliding prevention of heavy units on ships.

friction loops

Figure 3.2.6: Heavy unit secured to a flatrack by friction loops

Additional lashings must be applied in the form of half loops for the prevention of sliding.


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friction loops

horizontal half loops

Figure 3.2.7: Transverse sliding prevention by additional half loops

Cylindrically shaped units without securing points tempt the lasher to place lashings around

the body of the unit and fasten the ends to both sides. These so-called "silly loops" are not

able to secure a cargo unit against sliding, because the turn around the body does not provide

sufficient friction to counteract a load of the magnitude of MSL of the lashing.

silly loops

Figure 3.2.8: Inadequate transverse securing by silly loops

The adequate solution of securing such a unit is to use vertical half loops from both sides.

Each half loop is counted as two lashings.

vertical half loops

Figure 3.2.9: Proper transverse securing by vertical half loops

Another option for fastening direct lashings to a cargo unit without dedicated securing points

is the fitting of head loops. This may be used for longitudinal securing of a cylindrical unit,

where longitudinal half loops are not feasible.


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head loops

Figure 3.2.10: Longitudinal securing by direct lashings fastened to head loops

For securing a heavy wooden box against sliding, horizontal half loops should be kept low to

the rigid part of the box. If there is a risk of tipping, head loops should be used to fasten lash-

ings to the top of the box.

head loops

horizontal half loops

Figure 3.2.11: Securing a wooden box by half loops and head loops

3.2.5 Direct securing by lashings and stoppers

Occasionally, lifting fittings on heavy cargo units may also be used for securing. However,

there are often restrictions with regard to the permissible securing direction or available space

or amount of securing points on the ship, so that a combination of lashings and stoppers or

lashings and timber shores must be used.

Figure 3.2.12 shows a compact unit with lifting trunnions, bedded on double steel beams with

rubber mats underneath. The shown longitudinal stowage does not allow securing to the trun-

nions against transverse sliding, which is prevented by robust timber shore constructions. The

lashings attached to the trunnions prevent transverse tipping and longitudinal sliding.

Figure 3.2.13 shows the same unit in transverse stowage. The lashings attached to the trun-

nions prevent transverse sliding. Transverse tipping appears not to be critical at all. Longitu-

dinal sliding is prevented by stoppers welded to the steel beams, which are placed on rubber

mats.


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stbd port

Figure 3.2.12: Heavy unit secured against transverse tipping and longitudinal sliding

by lashings and against transverse sliding by timber shore constructions

port stbd

Figure 3.2.13: Heavy unit secured against transverse sliding and tipping by lashings

and against longitudinal sliding by welded stoppers

3.2.6 Homogeneity of mixed securing arrangements

The elasticity of different securing devices plays an important role in the performance of a

complex securing arrangement. The Annex 13 to the CSS-Code includes a safety factor of 1.5

as a divisor to the MSL for arriving at the smaller figure of CS. This safety factor is mainly

intended for compensating different elasticity's of the various securing devices. But it shall

also cover small deviations from the ideal securing direction and other variations.

This safety factor is certainly serving the purpose as long as no extreme differences of elastic-

ity exist, but may be insufficient for situations where, e.g., a large unit or a huge pile of pipes

is partly fixed by welded stoppers or stanchions and partly secured by long wire rope lashings.

If the discrepancy of elasticity's is extreme, then the only reasonable solution is to dimension

the stiff securing devices so that they can avoid sliding alone, while the more flexible securing

devices may be left for the protection against tipping or for compacting purposes.


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Figure 3.2.14: Unsuitable combination of different elasticity's

In such a situation it is useless to try to solve the problem by a high pre-tension of the flexible

securing device, e.g. wire rope lashings. As the high pre-tension must be applied to both sides,

the pre-tension forces compensate each other. Any additional external force must be counter-

acted by the stiff devices, e.g. stoppers, alone, because they restrict the movement of the unit

and prohibit any additional loading of the lashing. If the unit is liable to racking deformation,

the lashing will certainly prevent undue racking.

3.2.7 Desirable pre-tension in lashings

The obtainable pre-tension in a lashing depends on the technical means and on the engage-

ment and physical strength of the lashing workers. For usual turnbuckles in wire rope lashings

a pre-tension of 30 kN (3 t in the old phrasing) is the reasonable maximum. For chains with

lever tensioners plus extension the same figure may be obtained.

The pre-tension shall be kept as high as possible but must never exceed 50% of the MSL. In

practice, a pre-tension of 50% MSL is scarcely achievable. So there is hardly a risk to overdo

with pre-tensioning.

It is reasonable to apply pre-tensions in lashings of different elasticity's deliberately in a way

so that devices with a high elasticity get a high pre-tension and vice-versa, in order to obtain a

more homogeneous load distribution in an extreme load condition.

There is always a slackening of lashings observed when the ship is at sea. After some hours at

sea re-tightening is indispensable, with due re-tightening wire clips first.

3.3 Securing material

3.3.1 Material approved by Beluga-Shipping

Beluga ships are generally equipped with a standard outfit of securing material, which is listed

in the Lift/Lash Material Inventory. The MSL-figures declared by Beluga Shipping are partly

smaller than those allowed by IMO in the CSS-Code, Annex 13 due to higher safety factors

used by Beluga Shipping.

Standard lashing 10 ton MSL

Item dimensions BL MSLBeluga MSLIMO

Wire rope grommet 22 mm , 1, 2.5, 5, 10, 15, 25 m 263 kN 98 kN 118 kN

Shackle green pin 28 mm 500 kN 125 kN 250 kN

Shackle yellow pin 28 mm 500 kN 125 kN 250 kN

Turnbuckle eye-eye 44 mm , 457 mm take up 623 kN 156 kN 311 kN

Link chain 20 mm , 1.5 m 488 kN 122 kN 244 kN

Lashing plate 200 x 110 x 20 mm, 35 mm -- kN 98 kN -- kN


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The MSLIMO-figure for the wire rope grommet has been obtained as 30% of BL with factor

1.5 for narrow bend of the double wire. The MSLBeluga-figures are generally obtained by di-

viding the breaking strength by a safety factor of 4.

Standard lashing 8.5 ton MSL


Wire rope grommet 22 mm , 1, 2.5, 5, 10, 15, 25 m 263 kN 98 kN 118 kN

Shackle green pin 28 mm 500 kN 125 kN 250 kN

Shackle yellow pin 28 mm 500 kN 125 kN 250 kN

Turnbuckle eye-eye 32 mm , 457 or 305 mm take up 340 kN 85 kN 170 kN

Link chain 20 mm , 1 - 1.5 m 488 kN 122 kN 244 kN

Lashing plate 200 x 110 x 20 mm, 35 mm -- kN 98 kN -- kN

Other equipment


Lashing chain & lever 13 mm , 6 m 200 kN 100 kN 100 kN

Lashing belt & tensioner 50 mm width, 8 m 50 kN 25 kN 25 kN

Turnfoot D-ring LE 3 353 kN 176 kN 176 kN

Galvanised wire rope 16 mm (on coils of 220 m) 141 kN 80 kN 99 kN

Wire rope clips for 16 mm wire rope --- --- ---

The MSLIMO of the galvanised wire rope is taken as one-way material with 70% BL.

3.3.2 Assessment of other material

If for any reasons additional securing material must be purchased abroad, it is important to

obtain a document from the chandler or manufacturer stating the dimensions and the nominal

breaking load. It is, however, prudent to check the information given for plausibility.

The overview below shows securing material that is commonly used for securing break bulk

and project cargo, based on information supplied by the Annex 13 of the IMO CSS-Code. It

should be noted that these figures are not applicable for containers in standardised stowage,

where classification societies may use other safety factors, adapted to their system.

Material MSL

shackles, rings, deck eyes, turnbuckles of mild steel 50% of breaking strength

fibre ropes 33% of breaking strength

web lashings 50% of breaking strength

wire rope (single use) 80% of breaking strength

wire rope (re-useable) 30% of breaking strength

steel band (single use) 70% of breaking strength

chains of high tensile steel 50% of breaking strength

timber 0.3 kN per cm2

normal to the grain

For checking the information of the breaking load, as supplied by the manufacturer or chan-

dler, a set of rules of thumb are given in the following table, together with some supporting

remarks. The rule of thumb figures should be used for securing calculations only in those

cases where the supplied information appears uncertain or no information is available.

For high tensile steel material and for synthetic fibre material rules of thumb are not available.

Note: The diameter d in these rules of thumb must be entered in cm.


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Material / Elements BL [kN] MSL [kN] Remarks

Polypropylene rope 12 d2 33% of BL turn sticks for tightening must be

secured against re-winding Polyester rope 15 d2 33% of BL

Fibre belts document 50% of BL knotting of belts is prohibited

Wire rope of 6 x 19 + 1 FC or

6 x 37 + 1 FC 50 d

2 70% of BL one-way use (IMO permits 80%)

30% of BL re-usable material

Wire rope of 6 x 12 + 7 FC or

similar 25 d

2 70% of BL one way use (IMO permits 80%)

30% of BL re-usable material

Shackles of mild steel 20 d2 50% of BL measure bolt diameter

Turnbuckles of mild steel 20 d2 50% of BL measure thread diameter

Deck rings of mild steel 20 d2 50% of BL measure steel diameter of ring

Elements of high tensile steel document 50% of BL shackles, turnbuckles , D-rings

Chains of high tensile steel document 50% of BL long link & short link chains

Conifer timber shores - 1 kN/cm2

in line (parallel) to the grain

Conifer timber shores - 0.3 kN/cm2

normal (vertical) to the grain

Welded seams - 8 kN/cm2

for shearing load

Welded seams - 11 kN/cm2

for tension load

Steel band document 70% of BL not to be used for project cargo

A single weld leg should have a thickness a = 5 to 6 mm. Thus the MSLshear = 4 kN per cm

welded seam and MSLtension = 6 kN per cm welded seam.

3.3.3 Inspection and maintenance

Inspection and maintenance of both fixed and portable securing gear should be carried out

under the responsibility of the master. Reference is made to Chapter 2 of the approved Cargo

Securing Manual.

Visual inspection of all components being utilised should be completed at intervals not ex-

ceeding six months, aside from the usual inspection during loading/unloading. Defective

components must be immediately and effectively taken out of service, i.e. placed into a scrap

bin.

Components not being used after completion of work must be collected into a dedicated stor-

age place and protected from corrosion by salt water.

Actions of inspection and maintenance of the ship's cargo securing equipment must be docu-

mented in the appropriate Annex to the Cargo Securing Manual.

Threads of turnbuckles, shackle and bearings of twistlocks shall be regularly greased. Wire

rope grommets of the re-usable type shall be given conservation with wire rope grease.

Parts showing significant abrasion, corrosion or signs of cracks, or parts which are bent must

be discarded. If repair appears feasible the parts should be transferred to an authorised work-

shop or otherwise put into the scrap bin.

Discarded or missing parts must be replaced by equivalent parts. Appropriate manufacturer's

declaration documents must be received from the chandler and kept with the Cargo Securing

Manual.

Great care has to be taken, that securing elements, which have bee taken ashore inadvertently

during unloading, are returned immediately and be not replaced by other non-identical ele-

ments.


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Damage to fixed cargo securing elements must be repaired by an authorised workshop and

reported to the next classification society survey.

Discarded material as well as used one-way material must be disposed at a scrap yard. The

receipt of such disposal must be kept on board. Disposal of such material over board at sea is

not permitted on Beluga ships.

3.3.4 Welding standards

If deemed necessary for the safe securing of cargo, additional securing points or stoppers or

buttresses may be welded in appropriate positions under the strict observation of hot-work

procedures with the master's permission. Such welding shall be carried out by skilled persons

only. Reference is made to Chapter 2 of the approved Cargo Securing Manual.

Any welded attachments to the ship's deck, hatch cover, cargo hold plating, tank top or tween

deck pontoons must be aligned to stiffeners below the welding surface using an appropriate

weld area for absorbing the intended load.

Eye plates or lugs shall be aligned to the direction of the intended load.

D-rings of high tensile steel shall be welded to the deck or vertical structures in the ship by a

full penetration weld of several weld legs on both sides of the saddle in order to obtain the

nominal securing capacity. Preferably low hydrogen electrodes (lime basic electrodes) should

be used.

Stoppers must be welded to the deck or hatch cover in a way that welded seams are not sub-

jected to excessive torque.

Welding at or in close vicinity of fuel tanks is prohibited.

3.4 Determination of MSL of securing devices

Any calculated assessment of a securing arrangement, either by a simple rule of thumb or by

an advanced calculation method must be based on a sound input from the strength capacity of

the securing devices. It is therefore indispensable to obtain a clear picture of the available

MSL figures of the individual lashings, shores or stoppers.

3.4.1 Beluga standard lashings

The 10 ton standard lashing has an MSL = 98 kN, while the 8.5 ton version provides an MSL

= 83 kN. However, it is important also to assess the securing points at the cargo unit in order

obtain the final MSL of a particular Beluga standard lashing.

3.4.2 Securing points on cargo units

If the shipper has given the breaking strength BL of securing points on cargo units, the MSL

may be taken as 50% of this BL. If the shipper has given strength information in figures of

SWL for securing, then these should be directly taken as MSL-figures.

If lifting fittings in form of trunnions, plates or rings shall be used for securing and their

strength is supplied in figures of SWL for lifting, the MSL for securing may be taken as twice

the lifting SWL.

If no information is given, the rules of thumb under chapter 3.3.2 should be used.


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3.4.3 Conventional wire rope lashings

Types of wire ropes for lashing purposes

Mainly two types of wire rope should be used with regard to cost and ease of handling. These

are the flexible constructions of six strands with one or seven fibre cores. If not otherwise

specified by the manufacturer or chandler, the rules of thumb for the breaking load in chapter

3.3.2 above should be used.

The left type in Figure 3.4.1 with seven fibre cores is quite flexible and easy to use, but has

only about half the strength of the more common type with one fibre core.

6 x 12 + 7 FC BL = 25 x d

2

d d

6 x 19 + 1 FC BL = 50 x d

2

Figure 3.4.1: Suitable wire ropes for lashing purposes

Narrow bends and sharp corners

If a wire rope is guided around narrow bends or, moreover, around sharp corners, its strength

will be considerably reduced. The table below shows the residual strength as percentage of the

strength of the straight rope. It is important to note, that the strength reduction is more severe

if the rope is slipping in the bend.

ratio b/d 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

rope steady in the bend 50% 65% 72% 77% 81% 85% 89% 93% 96% 99%

rope slipping in the bend 25% 50% 60% 65% 70% 75% 79% 83% 87% 90%

Figure 3.4.2: Residual strength in a narrow bend

Sharp corners are much more aggressive to a wire rope. As a rule of thumb, the residual

strength after a 180° turn with sharp corners is 25% of the single straight wire rope, if steady

in the turn. If slipping at sharp corners, the strength is nominally reduced to zero.

In certain cases there is no other choice than using bolt holes or frame notches for fastening

lashings to a cargo unit, with the permission of the shipper. The MSL should then be carefully

established using the mentioned rule of thumb.


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Figure 3.4.3: Residual strength in a bolt hole with sharp corners

Doubling the wire rope at the sharp corners will be beneficial to the residual strength, as

shown in the figures below.

2 x 25% 2 x 25%

MSL = MSL of single wire

Figure 3.4.4: Doubling the wire at the sharp

corners of a notch

2 x 25%

2 x 25%

MSL = MSL of single wire

Figure 3.4.5: Spreading the load to two

notches

Application of wire rope clips

The reliable holding capacity of a wire rope clip depends on the tightness of the nuts. A well

done clip must press a visible dent into the wire with its U-bolt. The U-bolts should, as far as

possible, be placed on the dead end of the wire rope. In order to obtain the proper tightness of

a clip, the nuts or threads must be greased before tightening. A clip attached in this manner

may be attributed a holding capacity of about 10% of the breaking load of the wire rope.

Figure 3.4.6 shows the load transfer from the loaded part to the dead end of the rope under the

above assumption that the load in the bend is reduced by 40% of the force at the beginning of

the bend. The situation is well balanced with a load transfer of 10% BL per clip.

Figure 3.4.6: Transfer of loads with 10% BL per clip


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The correct assembly of a wire rope lashing must take into account:

Wire rope clip size should fit to the rope diameter,

U-bolt of clips should be attached to the dead end of the wire,

Number of clips should be at least as shown in Figures 3.4.7 to 3.4.9,

Nuts of clips must be greased before tightening,

Distance between clips should be at least 6-times wire diameter,

Dead ends must be secured against tangling open.

There are many ways to assemble a wire rope lashing in terms of forming an eye or loop, in-

clude a turnbuckle and connect it to the ship and the cargo. In any case, the clipped connec-

tion should be placed at a bend. Therefore, the following three types of wire lashings have

proved as reliable options.

double wire in bend

large bend diameter

Figure 3.4.7: Type A wire rope lashing

Type A is the favourite lashing type. It can be assembled and tightened in a convenient work-

ing position. The strength of shackle and turnbuckle should be consistent with the strength of

the double wire. If the upper bend has a diameter of less than 5 d, a reduction of strength of

the double wire must be considered. This also applies for the Type B wire lashing.

double wire in bend

large bend diameter

Figure 3.4.8: Type B wire rope lashing

Type B wire lashing should be used, if only turnbuckles of less strength are available. A good

pre-tightening before setting the wire clips is necessary because the turnbuckle has to pick up

the slack of both parts of the wire. It should be noted that in this option no shackle is neces-

sary and only 5 clips must be set in total.


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double wire in bend

Figure 3.4.9: Type C wire lashing

Type C wire lashing must be used with a stronger wire than in type A. It is the preferable type

for long lashings and for half loop lashings, which run over a unit and come back to the same

side.

A widespread mistake is to attach the wire clips in the open length of the wire lashing without

using a bend in between3.

"La-Paloma" lashing

Figure 3.4.10: Lashing with indeterminable MSL

The overall MSL of a wire rope lashing is the least MSL of the elements: wire rope, shackle,

turnbuckle, deck ring and the fitting on the cargo unit.

Figure 3.4.11: Correct assembly of Type A wire rope lashings

3 This lashing has been given the name "La-Paloma" lashing in memory of the lucky sailor presented by the

performer and vocalist Hans Albers.


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Figure 3.4.12: Wrong clips setting and MSL reduced due to single lay at sharp corners

Figure 3.4.13: "La Paloma"-lashing with indeterminable MSL

Figure 3.4.14: Too large angle of wires and "La Paloma"-connection

3.4.4 Chain-lashings and fibre belts

Chain-lashings with lever tensioners and fibre belts with ratchet tensioners are ready-made

lashings with an approved breaking strength and a documented MSL. But as with the Beluga

standard lashing it is important also to assess the securing points at the cargo unit and also on

the ship in order obtain the final MSL of the chain- or fibre lashing.

While chains are pretty stiff and fibre belts are highly flexible, an in-series combination of

both may be a suitable way to create a lashing with acceptable flexibility and persisting pre-

tension.


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Figure 3.4.15: Chain lashings

Figure 3.4.16: Web lashings

3.4.5 Welded stoppers

Beluga Shipping uses standardised stoppers, which are in majority simple stopper plates act-

ing against sliding of a cargo unit. In certain cases such stopper plates are modified to also

fulfil a clip function, i.e. secure the foot plate of a cargo unit against lifting and in this way to

prevent tipping of the unit.

When using stoppers a face plate shall be inserted between cargo and stopper. The face plate

shall be tag welded to the stopper.

Figure 3.4.17: Stoppers with and without face plate


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Figure 3.4.18: Stopper with clip function

The applicable MSL-figures for Beluga standardised stoppers have been determined by means

of advanced calculation programmes. The results are given in the tables below. Material used

shall have a minimum strength according to S355 or GL 360, with minimum yield strength of

355 N/mm2

(equal to 35.5 kN/cm2 or about 35.5 kg/mm

2). Thickness of welding seam is 8

mm. The MSL will be reduced if the thickness of welding seams is smaller.

L L

h h L1 h1

MSL

MSLvertical

MSLtransvers

simple stopper plate stopper plate with clip function

Figure 3.4.19: Standardised stoppers in the Beluga fleet

Ordinary stopper plate

L h t MSL

20 cm 15 cm 2 cm 150 kN

30 cm 15 cm 2 cm 200 kN

Stopper plate with clip function

L L1 h h1 t MSLtransvers MSLvertical

20 cm 15 cm 15 cm 5 cm 2 cm 100 kN 50 kN

30 cm 20 cm 15 cm 5 cm 2 cm 150 kN 80 kN

The MSLs of stoppers of different design or clips with other dimensions of the clips shall be

determined with approval from the Engineering Department of Beluga Shipping.

Figure 3.4.20: Corner stoppers made of angle profile sections


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Figure 3.4.21: Beam stopper vertically mounted

Figure 3.4.22: Beam stoppers strengthened by stiffeners

3.4.6 Timber shoring arrangements

Timber shoring arrangements for securing heavy cargo units must be solid constructions,

which do not disassemble in a slack condition. All elements must be well connected to each

other by strong nails or cramps. Additionally, timber shores must be stabilised by nailing

dunnage planks cross-wise onto the shores.

Figure 3.4.23: Principle of timber shore construction


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The pressure transferred from the cargo unit to the ship's structure must be distributed to

structural girders by means of crossbeams. Shores must be tightly fitted in and positioned on

benches. Crossbeams must overlap the shores on each end.

Timber shores that are intended to transfer securing forces from cargo units to rigid structures

of a vessel are given a nominal MSL of 0.3 kN per cm2. This figure applies to the crossbeams,

where the force acts "normal" or vertical to the timber grain. The shores actually transfer the

force along the grain with a permissible load of about 1 kN per cm2, but the MSL must reflect

the weakest part of the construction, which moreover may also be the cargo unit itself.

Since timber shores are subject to pressure, the risk of buckling behaviour restricts the free

length of a timber. If the external force shall be restricted to the permissible MSL = 0.3

cross-section a2 in cm

2, then the free length of a shore must be limited to:

lperm = 25 a [cm]

This formula is based on the assumption that the shore is not loaded higher than its MSL. If

there is doubt about this limitation, the free length should be made shorter.

Figure 3.4.24: Shoring arrangement with horizontal crossbeams

Figure 3.4.25: Shoring arrangement with vertical crossbeams

Figure 3.4.26: Timber shoring construction with intermediate stabilising members


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Figure 3.4.27: Transverse and longitudinal shoring of concrete pipes

Figure 3.4.28: Shores between bedding cradles

Figure 3.4.29: Shores on benches between cargo units

3.5 Securing calculation

The 1994 amendment of the IMO CSS-Code has presented a new Annex 13 with the title

"Methods to assess the efficiency of securing arrangements for non-standardised cargo". This

Annex 13 enables the maritime community to use an internationally agreed approach for non-

standardised cargo securing calculations, which meanwhile has been accepted worldwide by

ship operators as well as in legal disputes.

3.5.1 Annex 13 Rule-of-thumb

Rules-of-thumb, as given in chapter 3.2.1 of this document, may be used for a raw estimation

of the lashing effort. Another rule-of-thumb is provided by the Annex 13 that reads:


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The total of the MSL values of the securing devices on each side of a unit of cargo (port

as well as starboard) should equal the weight of the unit.

It must be noted that this rule does not take the size or speed of the vessel into account, nei-

ther her stability nor the location of stowage in the ship. It further addresses only the weight

of the unit, but not its dimensions, which may become important for forces by wind and sea-

sloshing. The rule ignores the effect of lashing angles and friction at the stowage place, but an

explanatory text in the IMO Code reminds that lashing angles to the deck should not be

greater than 60° and care should be taken for adequate friction.

On ships of the Beluga fleet the above rule-of-thumb should not be used except for small

items in under deck stowage.

3.5.2 Annex 13 Advanced Calculation Method

The advanced calculation method, presented in the Annex 13 to the CSS-Code, is still a sim-

plified model of the reality, but it has certain advantages against the various even more simple

rules-of-thumb. In order to obtain reliable results from the advanced calculation method cer-

tain typical misuse practices must be avoided:

- Use of invalid MSL-figures in the balances of forces and moments,

- Ignorance of limiting conditions, as lined out in the Annex 13,

- Mixing with elements of other calculation methods,

- Converting the balance formulas into target oriented equations,

- Non-observance of SI-units.

3.5.3 Annex 13 Alternative Calculation Method

The alternative calculation method has been developed in IMO, on the initiative of the late

marine surveyor Capt. Edward Boyle, NCB New York, and adopted in 2002. It contains only

minor changes to the basic advanced calculation method and does not replace the latter. The

changes are:

- Horizontal lashing angles are taken into account.

This is the key issue of the improvement and solves the frequent question on how to treat a

lashing at, e.g 45° to the transverse direction. However, the amount of entry data to the calcu-

lation is considerably increased and it is advisable to use an approved computer program for

avoiding calculation errors within the processing of the lashing data.

- Calculation strength CS = MSL/1.35.

This is a consequence to the more precise consideration of horizontal lashing angles, which

allows to reduce the safety factor.

- Small changes in the balance calculation.

The changes are insignificant, in particular if a computer program is used. The amended ver-

sion of the Annex 13 contains a calculated example, which demonstrates that each lashing

must be treated separately, duly distinguishing its direction of action (fore, aft, port, stbd). For

each lashing two f-values must be taken from an appropriate table with the entries of the ver-

tical and the horizontal lashing angle, and utilised within the applicable balance.


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3.5.4 Computer based calculation

There are numerous versions of suitable computer programs for the application of the ad-

vanced and the alternative calculation method presented by the Annex 13. One of the most

commonly used is the LashConTM

by Olav Lyngstad, available from Det Norske Veritas. This

program has been introduced in the Beluga fleet.

The program offers to chose between the basic advanced calculation method and the alterna-

tive method with recommendation of the latter. It provides a storage stack where a number of

calculated cases can be stored. It also offers print-outs of each page. The calculated accelera-

tions can be replaced by figures adapted to conditions in sheltered waters.

However, there are several minor drawbacks, which must be known and overcome on occa-

sion by manual calculation or by using LashCon in a dual approach.

- The program does not offer intermediate entries for the stowage levels. This may be-

come particularly important for interpolation between the stowage levels "on deck low"

and "on deck high".

- The program does not allow to exclude steep transverse lashings from the transverse

sliding balance while using the same lashings for the transverse tipping balance.

- The program does not use tipping prevention levers "c", as proposed by the Annex 13.

These levers are expressed by c = d sin, where d is the horizontal distance from the

tipping axis to the securing point on the deck. This approach appears easier to handle but

fails if the securing point is not on deck but higher, e.g. on the ship's side in the tween

deck or lower hold.

- In the basic advanced method the program requires to enter a lashing a second time for

checking the effect from it longitudinal component,

- The number of securing devices is limited to 10. Grouping of devices is therefore indis-

pensable in larger securing arrangements. This may become difficult with the alternative

method.

3.5.5 Additional tipping moment for very large cargo units

The tipping moment acting on a cargo unit in heavy weather, as stipulated by the Annex 13 to

the CSS-Code, is simply derived from the nominal transverse or longitudinal force Fy or Fx,

multiplied with the vertical distance of the force vector from the tipping axis.

However, there is an additional tipping moment resulting from rotational inertia of a cargo

unit when subjected to the rotational acceleration of a rolling or pitching vessel. This moment

is independent from the location of stowage in the ship.

The Annex 13 to the CSS-Code does not take this additional moment into account, because it

is of negligible magnitude for usual cargo units and also heavy lift units of moderate size.

Only for very large units, like offshore modules, huge cranes, huge straddle carriers, this addi-

tional tipping moment should be accounted for, in particular, if tipping becomes a critical cri-

terion.

Transverse tipping

The following formula determines this additional tipping moment in a rolling motion:

Madd = ''max m ip2 [kNm]

with Madd = additional tipping moment [kNm]

''max = maximum angular acceleration of the vessel [s-2

]


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m = mass of the cargo unit [t]

ip = polar radius of inertia of the cargo unit [m]

ship acceleration

additional tipping moment from inertia ordinary tipping

moment = Fya

tipping axis

tipping lever a

centre of rotation

transverse force Fy

z

Figure 3.5.1: Additional tipping moment of large cargo units

The additional tipping moment cannot be determined by means of data provided in the Annex

13 to the CSS-Code. The following tools for obtaining figures for ''max and ip are given:

The angular acceleration ''max is calculated on the basis of a harmonic roll with the amplitude

and a rolling period T, which must be estimated from the metacentric height GMC by the

well known formula:

C

GM

B78.0T

[s] (B = breadth of ship [m])

The roll amplitude should be taken as 30°. Then ''max is obtained by formula:

2

maxT

2

[s

-2]

For ease of reference the following table is offered for = 30° roll amplitude:

T [s] 8 9 10 11 12 13 14 15 16 17 128 19 20

''max [s-2

] 0.32 0.26 0.21 0.17 0.14 0.12 0.11 0.09 0.08 0.07 0.06 0.06 0.05

The polar radius of inertia of the cargo unit ip depends on the cross-section of the cargo unit in

the plane of tipping. There are several formulae available for estimating ip.

If the mass of a square shaped unit is homogeneously distributed within the limits of length,

width and height, then

3

hw

2

1i

22

p

= 0.289 22 hw [m]

If the mass of a square shaped unit is concentrated in the shell of the unit, i.e. the unit is a hol-

low body, then


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12

hwi

p

= 0.289 (w + h) [m]

If the mass of a cylindrical unit is homogeneously distributed within the limits of length and

diameter d, then

8

di

p = 0.354 d [m]

If the mass of a cylindrical unit is concentrated in the shell of the unit, i.e. the unit is a hollow

cylinder, then

2

di

p = 0.5 d [m]

w

l

ip

h

ip l

w

h

Figure 3.5.2: Polar radius of inertia ip for a full square shaped body (left)

and a hollow square shaped body (right)

Longitudinal tipping

A similar consideration for tipping in the longitudinal direction should consider a pitching

period T = 0.5 Lpp seconds and a pitching amplitude of 15°. This includes a moderate

slamming shock. The additional tipping moment in longitudinal direction may become sig-

nificant due to the generally short pitching periods of 5 to 6 seconds.

Figure: 3.5.3: Cargo units with large polar radius of inertia


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4. Stowage and securing of break bulk

4.1 Pipes stowed on deck

4.1.1 Stowage and securing principles

A deck cargo of pipes must be secured according to the principles of the CSS-Code, and the

securing arrangement should be assessed by the Annex 13 method. This assessment method is

applicable for direct securing only and not for friction securing (over-the-top lashings).

The concept of "direct securing" should be governed by the following conditions:

- The pipes must be stowed longitudinally on the ship.

- The pipes may be looked at as a single block of cargo only under the pre-condition that

they are placed tightly by each other in the lower tier, preferably with rubber mat lining

between each other, the second and further tiers stowed into the grooves of the bottom

tier and lined with friction increasing material, preferably rubber mats.

- Over-the-top lashings must be set for compacting the stow.

- The lower tier must be placed on boards of soft timber for providing friction to the hatch

cover and wedges must be used to prevent rolling of the pipes while the loading process

is going on. The wedges should be fixed by nails to the bottom timbers.

- Transverse sliding must be prevented by direct securing means, preferably solid stan-

chions.

- Longitudinal sliding must be prevented by welded stoppers to the lower tier of pipes and

by friction between layers.

- Tipping is not considered to present a problem in this case.

The height h of such a stack of n tiers of pipes with diameter d in metres is:

3

2

)1n(1dh [m]

4.1.2 Securing alternative 1

Transverse sliding is prevented by a sufficient number of vertical "half loop" lashings made

of wire rope and tightened by turnbuckles (see Figure 4.1.1).

Compacting: The lashings applied for the prevention of transverse sliding do also serve for

the necessary compacting.

Longitudinal sliding is prevented by stoppers welded to the hatch top, lined with timber

chocks for avoiding damage to the pipes in the bottom tier. The upper tiers are fixed to the

lower by friction from rubber lining with = 0.6.

Caution:

It should be noted that with this alternative the block of pipes would shift considerably during

heavy rolling between extreme port and starboard roll due to the elasticity of the long lashing

wires. Therefore this alternative is not recommended for a block of pipes covering the full

width of the deck space of the vessel.


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Figure 4.1.1: Transverse securing with vertical half loops


Transverse sliding is prevented by a sufficient number of horizontal "half loop" lashings

made of wire rope and tightened by turnbuckles (see Figure 4.1.2). These lashing are some-

times also called "spring lashings" and are guided longitudinally through the pipes with both

ends fastened to D-rings on the hatch top.

Compacting: A sufficient number of over-the-top lashings must serve for the necessary com-

pacting.

Longitudinal sliding is prevented by stoppers welded to the hatch top, lined with timber

chocks for avoiding damage to the pipes in the bottom tier. The upper tiers are fixed to the


Comment:

Although the elasticity of this alternative is less due to the shorter lashing wires, a serious

problem with may arise by the sensitive corners of the pipes, which of course must be

shielded by edge protectors. But these may be wasted by the permanent sawing effect of the

stretching and contracting wires, if the ship starts to roll.

Figure 4.1.2: Securing alternative 2 with horizontal half loops to both sides


Transverse sliding is prevented by a sufficient number of stanchions with buttresses to the

deck (see Figure 4.1.3) or an equivalent construction.


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Compacting: A sufficient number of over-the-top lashings must serve for the necessary com-

pacting.

Longitudinal sliding must be prevented by stoppers welded to the hatch top, lined with tim-

ber chocks for avoiding damage to the pipes in the bottom tier. The upper tiers are fixed to the


Figure 4.1.3: Securing alternative 3 with solid stanchions on both sides

Comments:

In this alternative the transverse motion of the block of pipes in rolling motions of the ship is

close to zero. Additional horizontal or vertical "half loop" lashings would therefore be useless.

Hence, it is of utmost importance that the stanchions alone are strong enough to keep the

block in place, together with the share contributed by friction to the timber battens on the

hatch top. It would be a substantial shortcoming if the securing effort would be partitioned

between "half loops" of considerable length and relatively stiff stanchions.

The "friction loops" cannot be reflected in the balance of forces above although they certainly

contribute by increasing the friction, as long as the pre-tension remains in the wires. Anyway,

their share is comparatively small, but necessary to keep the top layers of pipes in place.

4.1.5 Longitudinal securing

The three alternatives above are distinguished by the method of transverse securing, where

sliding prevention may be obtained by sufficient strength of lashings or stanchions. However,

securing against longitudinal sliding may become difficult, particularly in the forward part of

the ship, because the friction between the upper layers of pipes dictates the limits.

If the sliding balance shows negative results for the upper tiers, and there is no simple means

to secure these tiers longitudinally, the master should be instructed to reduce the speed in case

of threat of slamming.

Even pipes stowed under deck need protection against longitudinal sliding. This may be ef-

fected by blocking the pipe ends in the upper tier with timber to transverse bulkheads or solid

tiers of other cargo or by jamming the top layer of pipes against the underside of decks or

hatch covers by means of air bags. Rubber mats between the layers of pipes are always help-

ful in this respect.

4.1.6 Technical details

Ensuring a compact block

The assumption that the stacked pipes may be treated as one compact block of cargo is only

justified if all the pipes have good contact among each other. Pipes within the stack should

have six lines of contact to adjacent pipes. Pipes in the bottom will have only five, and pipes

at the top and the sides only four such lines of contact. Pipes at the upper and lower corners of


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the stack, although having only three lines of contact, are quite well merged to the stack by

the pressure of lashings.

line of contact

Figure 4.1.4: Ideal lines of contact

However, there may be several handicaps that may prevent a good contact between the pipes.

Pipes are not always 100% straight but may show a slight curve. Thus contact at the ends

may give space in the middle or vice versa.

Pipes may be shipped with so-called "spacers" made of polyethylene rope wrapped

around the pipe at a few metres distance. The spacers are compressed during rolling and

produce slack in the stack of pipes.

Wedges may be pre-fitted on the bottom dunnage by means of templates. This may lead

to inaccuracies in the stowage of pipes.

Rubber mats should be used between the pipes at all lines of contact. If poly-rope spacers

are attached to the pipes, the rubber mats may be ineffective if they are thinner than the

ropes.

Protection of pipes

Pipes are often shipped with bevel protectors. These are made of steel or aluminium or plastic

material and must not be damaged or removed.

root face

outside

inside

bevel

bevel protector

Figure 4.1.5: Bevel protector

If pipes are coated on their outside, so-called chicken-ladders must be used at the places

where wire lashing are guided around. These chicken-ladders are made of short soft wood

boards connected to each other by tacked-on fibre ropes or plastic tapes.

If lashings are guided through pipes, as shown in the securing alternative 2, so-called edge

protectors must be used. These are ready-made plate angles of steel or aluminium with bulges

for guiding the wire.

If the pipes are coated inside, e.g. by the special "flow-coat" used for gas-pipes, a direct con-

tact of the wires to the pipes must be avoided by slipped-on pieces of rubber hose.

Most pipes are welded with a longitudinal seam. Shippers usually require the stowage with

the seam in 12 o'clock position in order to avoid chafing damage to other pipes. Sometimes

pipes are shipped with spiral seams. For those only spacers can avoid the chafing contact.

Construction of stanchions

There are certainly a number of alternatives for the construction of stanchions. The consider-

able cost for such stanchions justifies a re-usable concept, if repeated shipments of pipes are


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carried. Three different concepts are presented. They must be designed to purpose and ap-

proved by Beluga Shipping.

Concept 1 is in some way similar to that used also for timber deck cargo. It consists of H-

beams, which are vertically inserted into two steel lugs and chocked with timber. This ar-

rangement requires a strength of the upper lug of the desired MSL multiplied by h/(h-d) and a

section modulus of the H-beam that can resist the bending moment MSL d with a bending

stress of not more than about 20 kN/cm2.

MSL

MSLh/h-d

d

h

MSLd/h-d

Figure 4.1.6: Stanchion by concept 1

Concept 2 may be applied if the hatch coaming does not permit the welding of lugs. It con-

sists of H-beams of less sectional dimensions than concept 1, but needs fittings for bolting it

to the deck and connecting it to a buttress with similar fittings for taking the transverse load.

The dimensions of the stanchion and the buttress as well as the pedestals on deck must be able

to withstand the tension and pressure forces shown in Figure 4.1.7. There is no significant

bending moment in this concept, but the buttress must resist buckling.

MSL

MSL


Concept 3 consists of H-beam stanchions welded to the hatch cover. This option may be ap-

plied if the hatch cover is strong enough for taking the required MSL. Generally, the stan-

chions must be short in order not to place undue stress to the plating of the hatch cover. The

H-beams may be doubled or otherwise strengthened for obtaining the necessary section

modulus.

MSL



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4.2 Mixed cargo

This chapter addresses the stowage and securing of various cargo items, which are relatively

light and small, so that individual securing of each item may be not feasible. Therefore care

must be taken to provide a tight stow of the block and apply securing measures for groups of

items, where necessary.

4.2.1 Cross-stowage

Cross-stowage means a stowage pattern where the cargo is tightly stuffed and supported

against transverse forces by the sides of the cargo space or other fixed structures like longitu-

dinal bulkheads, requiring minimal securing effort in general by blocking with timber shores.

Figure 4.2.1: Cross-stowage of cable reels, compacted by wire lashings

Figure 4.2.2: Cross-stowage of concrete pipes, secured by timber shoring


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Figure 4.2.3: Cross-stowage of wooden boxes, secured by timber shoring

Figure 4.2.4: Cross-stowage of steel constructions, secured by timber shoring

Figure 4.2.5: Cross-stowage of steel drums on pallets, secured by timber shoring


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4.2.2 Side-stowage

Side stowage means a stowage pattern where support against transverse forces is given by

fixed ship's structures from one side only. There is a need for transverse securing to the other

side as well as some longitudinal securing in many cases. Securing a side stowage pattern is

mainly achieved by half-loop lashings.

Figure 4.2.6: Side-stowage of wooden boxes, provisionally secured by web lashings

4.2.3 Longitudinal securing

Securing against longitudinal forces is required in particular in cargo spaces forward in the

ship, where friction may be reduced due to temporary vertical forces from pitching motions of

the vessel.

Figure 4.2.7: Longitudinal securing of a cross-stowage pattern

4.2.4 Use of timber dunnage

Timber dunnage in the form of wooden planks or plywood-boards must be used under cargo

items whenever there is a need to provide good friction, in particular under cargo items with a

metallic or otherwise smooth bottom.


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Figure 4.2.8: Timber dunnage flooring for creating friction

Timber must also be used under cargo for handling slings during loading and unloading.

Figure 4.2.9: Timber squares under steel plates for handling the chain slings

Timber dunnage, plywood boards or square timbers must be used between layers of cargo

items, whenever there is a need to equalise an uneven surface and/or to provide a compact

stowage block.

Figure 4.2.10: Plywood boards for stabilising an IBC-stow


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Figure 4.2.11: Dunnage flooring for stabilising top stowage of wooden crates

Figure 4.2.12: Timber squares for levelling a stow of steel construction parts

Guideline for Project Cargo Operations

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