MSC.1/Circ.1623

7 December 2020

AMENDMENTS TO THE CODE OF SAFE PRACTICE FOR CARGO STOWAGE AND SECURING (CSS CODE)

1 The Maritime Safety Committee, at its 102nd session (4 to 11 November 2020), approved amendments to the Code of Safe Practice for Cargo Stowage and Securing (CSS Code), as prepared by the Sub-Committee on Carriage of Cargoes and Containers, at its sixth session (9 to 13 September 2019), as set out in the annex.

2 Member States are invited to bring the amendments to the attention of shipowners, ship operators, ship masters and crews and all parties concerned.

ANNEX

AMENDMENTS TO THE CODE OF SAFE PRACTICE FOR CARGO STOWAGE AND SECURING (CSS CODE)

ANNEX 13

Methods to assess the efficiency of securing arrangements

For semi-standardized and non-standardized cargo

The complete text of annex 13, together with its four appendices, is replaced by the following:

"1 Scope of application

1.1 The methods described in this annex should be applied to semi-standardized and non-standardized cargo including very heavy and/or very large cargo items. Standardized stowage and securing systems, in particular containers on containerships, are excluded.

1.2 Cargoes carried on towed barges should be secured according to the provisions of this annex except that the assumed external forces may be determined using an alternative method acceptable to the Administration instead of that described in section 7.1 of this annex.

1.3 Very heavy and/or very large cargo items as addressed in chapter 1.8 of this Code may require provisions and considerations beyond the general scope of this annex. Examples of such provisions and considerations are given in appendix 3 of this annex.

1.4 Semi-standardized cargoes, for which the securing arrangements are often designed based on worst case assumptions on cargo properties, lashing angles and stowage positions on board, may require provisions and considerations beyond the general scope of this annex. Examples of such provisions and considerations are given in appendix 4 of this annex.

1.5 Notwithstanding the general principles contained in this annex, the adequacy of cargo securing may be demonstrated by means of detailed engineering calculations based upon the general principles and encompassing the additional provisions and considerations shown in appendix 3 of this annex. Computer programs used for that purpose should be validated against a suitable range of model tests or full-scale results in irregular seas. When using new software for new and unconventional applications, the validation should be documented.

1.6 The application of the methods described in this annex is supplementary to the principles of good seamanship and should not replace experience in stowage and securing practice.

2 Purpose of the methods

The methods should:

.1 provide guidance for the preparation of Cargo Securing Manuals and the examples therein;

.2 assist ship's staff in assessing the securing of cargo items not covered by the Cargo Securing Manual;

.3 assist qualified shore personnel in assessing the securing of cargo items not covered by the Cargo Securing Manual; and

.4 serve as a reference for maritime and port-related education and training.

3 Presentation of the methods

The methods are presented in a universally applicable and flexible way. It is recommended that designers of Cargo Securing Manuals convert this presentation into a format suiting the particular ship, its securing equipment and the cargo carried. This format may include applicable diagrams, tables or calculated examples.

4 Strength of securing equipment

4.1 Manufacturers of securing equipment should at least supply information on the nominal breaking strength of the equipment in kilonewtons (kN)1.

______________

1 1 kN ≈ 100 kg.

4.2 "Maximum securing load" (MSL) is a term used to define the load capacity for a device used to secure cargo to a ship. "Safe working load" (SWL) may be substituted for MSL for securing purposes, provided this is equal to or exceeds the strength defined by MSL.

Where practicable, the MSL should preferably be marked on the securing equipment.

The MSLs for different securing devices are given in table 1 if not given under 4.3.

The MSL of timber should be taken as 0.3 kN/cm2 normal to the grain.

Table 1 - Determination of MSL from breaking strength

Material

MSL

Shackles, rings, deckeyes, turnbuckles of mild steel

50% of breaking strength

Fibre rope

33% of breaking strength

Web lashing

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

50% of breaking strength

4.3 Particular securing devices (e.g. fibre straps with tensioners or special equipment for securing containers) may be marked with a permissible working load, as prescribed by an appropriate authority. This may be taken as the MSL.

4.4 When the components of a lashing device are connected in series (e.g. a wire to a shackle to a deckeye), the minimum MSL in the series should apply to that device.

4.5 Where temporary welded fittings are used, they should be designed to be adequate for the expected loading, and installed by qualified welders in accordance with established welding procedures. The design and placement of these fittings should be such as to minimize bending.

 

4.6 Simple stoppers may be used to provide securing against sliding. These are generally welded to a surface by fillet welds, characterized by thickness (a) and length (l). A face plate should be provided against the cargo piece so that welds are not loaded by a shear force at right angles to the weld direction or by significant bending forces. As a simple rule of thumb for welded steel stoppers, the MSL of single-lay weld leg can then be approximated as 4 kN/cm (l) normal to the face plate, assuming 5 mm weld thickness (a). For a triple-lay weld leg, MSL can be taken as 10 kN/cm normal to the face plate.

 

Figure 16.1 - Welding of steel stoppers

4.7 All securing devices to be accounted for in the balance calculations described in this annex should be capable of transferring forces directly from the vessel to the cargo or vice versa, in order to reflect their MSLs. For that purpose, lashings should be attached to fixed securing points or strong supporting structures marked on the cargo item or advised as being suitable, or taken as a loop around the item with both ends secured to the same side as shown in figure 7 in annex 5 of the Code. Lashings going over the top of the cargo item, whose only function is to increase friction by their pre-tension, cannot be credited in the evaluation of securing arrangements under this annex.

5 Rule-of-thumb method

5.1 The total of the MSL values of the securing devices on each side of a cargo item (port as well as starboard) should equal the weight of the item.2

______________

2 The weight of the unit should be taken in kN.

5.2 This method, which implies a transverse acceleration of 1g (9.81 m/s2), applies to nearly any size of ship, regardless of the location of stowage, stability and loading condition, season and area of operation. The method, however, takes into account neither the adverse effects of lashing angles and non-homogeneous distribution of forces among the securing devices nor the favourable effect of friction.

5.3 Transverse lashing angles to the deck should not be greater than 60 and it is important that adequate friction is provided by the use of suitable material. Additional lashings at angles of greater than 60 may be desirable to prevent tipping but are not to be counted in the number of lashings under the rule of thumb.

6 Safety factor

6.1 When using balance calculation methods for assessing the strength of the securing devices, a safety factor is used to take account of the possibility of uneven distribution of forces among the devices or reduced capability due to the improper assembly of the devices or other reasons. This safety factor is used in the formula to derive the calculated strength (CS) from the MSL and shown in the relevant method used.

6.2 Notwithstanding the introduction of such a safety factor, care should be taken to use securing elements of similar material and length in order to provide a uniform elastic behaviour within the arrangement.

6.3 If securing devices of different elasticity are used in the same direction, e.g. welded bottom stoppers and fibre belts or long wire lashings, the more flexible securing devices in such an arrangement should be excluded if they, due to their elongation, do not contribute to preventing initial movement of the cargo.

7 Advanced calculation method

7.1 Assumption of external forces

7.1.1 External forces to a cargo item in longitudinal, transverse and vertical directions should be obtained using the formula:

F(x,y,z) = m a(x,y,z) + Fw(x,y) + Fs(x,y)

where

F(x,y,z) = longitudinal, transverse and vertical forces

m = mass of the item

a(x,y,z) = longitudinal, transverse and vertical accelerations (see table 2 below)

Fw(x,y) = longitudinal and transverse forces by wind pressure

Fs(x,y) = longitudinal and transverse forces by sea sloshing.

The basic acceleration data are presented in table 2.

Table 2 - Basic acceleration data

 

 

Remarks:

The given transverse acceleration figures include components of gravity, pitch and heave parallel to the deck. The given vertical acceleration figures do not include the static weight component.

 

7.1.2 The basic acceleration data are to be considered as valid under the following operational conditions:3

________________

3 The acceleration values in table 2 are calculated according to the guidance formulae for acceleration components in the IGC Code (resolution MSC.5(48)) and reduced to a probability level of 25 days.

.1 operation in unrestricted area;

.2 operation during the whole year;

.3 length of ship is 100 m;

.4 service speed is 15 knots; and

.5 B/GM ≥ 13 (B = moulded breadth of ship, GM = metacentric height).

7.1.3 For operation in a restricted area, reduction factors for accelerations may be considered, taking into account the season of the year, the accuracy of the weather forecast affecting the wave heights during the intended voyage and the duration of the voyage. Restricted area means any sea area in which the weather can be forecast for the entire sea voyage or shelter can be found during the voyage.

7.1.4 Reduction factors, fR, may be applied to significant wave heights4, Hs, not exceeding 12 m for the design of securing arrangements in any of the following cases:

________________

4 Arithmetic mean of the highest one third of waves measured from trough to crest.

.1 The required securing arrangement is calculated for the maximum expected 20-year significant wave height in a particular restricted area and the cargo is always secured according to the designed arrangement when operating in that area.

.2 The maximum significant wave height that a particular securing arrangement can withstand is calculated and the vessel is limited to operating only in significant wave heights up to the maximum calculated. Procedures for ensuring that any operational limitation is not exceeded should be developed and followed and documented in the ship's approved Cargo Securing Manual.

.3 Required securing arrangements are designed for different significant wave heights and the securing arrangement is selected according to the maximum expected wave height for each voyage for which an accurate weather forecast is available. Thus, the duration of the voyage should not exceed 72 hours or a duration as accepted by the Administration.

7.1.5 The basic acceleration data in table 2 may be multiplied by the following reduction factor:

fR = 1 - (Hs - 13)² / 240,

 

where Hs is:

 

.1 the maximum expected 20-year significant wave height in the area according to ocean wave statistics; or

.2 the maximum predicted significant wave height on which the operational limitations are based; or

.3 for voyages not exceeding 72 hours the maximum predicted significant wave height according to weather forecasts.

7.1.6 When weather-dependent lashing is applied, operational procedures for the following activities should be developed, followed and documented in the ship's approved Cargo Securing Manual, or otherwise included in the ship's safety management system:

.1 decision on the level of cargo securing based on the length of the voyage and the weather forecast;

.2 communication to all concerned parties of the decided level of cargo securing for the intended voyage;

.3 execution and supervision of appropriate cargo securing efforts in accordance with the Cargo Securing Manual; and

.4 monitoring of environmental conditions and ship motions to ensure that the applied level of cargo securing is not exceeded.

7.1.7 For ships of a length other than 100 m and a service speed other than 15 knots, the acceleration figures should be multiplied by a correction factor given in table 3.

Table 3 - Correction factors for length and service speed

Length (m)

Speed (kn)

50

60

70

80

90

100

120

140

160

180

200

9

1.20

1.09

1.00

0.92

0.85

0.79

0.70

0.63

0.57

0.53

0.49

12

1.34

1.22

1.12

1.03

0.96

0.90

0.79

0.72

0.65

0.60

0.56

15

1.49

1.36

1.24

1.15

1.07

1.00

0.89

0.80

0.73

0.68

0.63

18

1.64

1.49

1.37

1.27

1.18

1.10

0.98

0.89

0.82

0.76

0.71

21

1.78

1.62

1.49

1.38

1.29

1.21

1.08

0.98

0.90

0.83

0.78

24

1.93

1.76

1.62

1.50

1.40

1.31

1.17

1.07

0.98

0.91

0.85

7.1.8 For length/speed combinations not directly tabulated, the following formula may be used to obtain the correction factor with v = speed in knots and L = length between perpendiculars in metres:

 

This formula should not be used for ship lengths less than 50 m or more than 300 m.

In addition, for ships with B/GM less than 13, the transverse acceleration figures should be multiplied by the correction factor given in table 4.

Table 4 - Correction factors for B/GM

B/GM

3

4

5

6

7

8

9

10

11

12

13 or above

on deck, high

2.64

2.28

1.98

1.74

1.56

1.40

1.27

1.19

1.11

1.05

1.00

on deck, low

2.18

1.93

1.72

1.55

1.42

1.30

1.21

1.14

1.09

1.04

1.00

'tween deck

1.62

1.51

1.41

1.33

1.26

1.19

1.14

1.09

1.06

1.03

1.00

lower hold

1.24

1.23

1.20

1.18

1.15

1.12

1.09

1.06

1.04

1.02

1.00

7.1.9 The following should be observed:

.1 In the case of marked roll resonance with amplitudes above 30, the given figures of transverse acceleration may be exceeded. Effective measures should be taken to avoid this condition.

.2 In the case of heading into the seas at high speed with marked slamming impacts, the given figures of longitudinal and vertical acceleration may be exceeded. An appropriate reduction of speed should be considered.

.3 In the case of running before large stern or quartering seas with a stability which does not amply exceed the accepted minimum requirements, large roll amplitudes must be expected with transverse accelerations greater than the figures given. An appropriate change of heading should be considered.

.4 Forces by wind and sea to cargo items above the weather deck should be accounted for by a simple approach:

.1 force by wind pressure = 1 kN per m2

.2 force by sea sloshing = 1 kN per m2

.5 The wind force may be reduced by the same principles as the accelerations, i.e. multiplying it with a reduction factor, fR, based on the expected significant wave height.

.6 Sloshing by sea can induce forces much greater than the figure given above. This figure should be considered as remaining unavoidable after adequate measures to prevent overcoming seas.

.7 Sea sloshing forces need only be applied to a height of deck cargo up to 2 m above the weather deck or hatch top.

.8 For voyages in a restricted area and with forecast wave heights for which no sea sloshing is expected, sea sloshing forces may be neglected.

7.2 Balance of forces and moments

7.2.1 The balance calculation should preferably be carried out for:

.1 transverse sliding in port and starboard directions;

.2 transverse tipping in port and starboard directions; and

.3 longitudinal sliding under conditions of reduced friction in forward and aft directions.

7.2.2 In the case of symmetrical securing arrangements, one appropriate calculation for each case above is sufficient.

7.2.3 Friction contributes towards prevention of sliding. The following friction coefficients (μ) should be applied.

Table 5 - Friction coefficients

Materials in contact

Friction coefficient (μ)

Timber-timber, wet or dry

0.4

Steel-timber or steel-rubber

0.3

Steel-steel, dry

0.1

Steel-steel, wet

0.0

A friction increasing material or deck coating with higher friction coefficients may be used assuming a certified conservative friction coefficient and the endurable shear stress of the material under repeated loads, as they occur in heavy weather at sea. The applicability of these data should be reviewed with due consideration of the prevailing conditions in terms of moisture, dust, greasy dirt, frost, ice or snow as well as the local pressure applied (weight per area) to the material. Specific advice on this matter as well as instructions for maintenance of coatings should be included in the ship's Cargo Securing Manual, if appropriate.

7.2.4 Transverse sliding

7.2.4.1 The balance calculation should meet the following condition (see also figure 17):

Fy ≤ μ m g + CS1 f1 + CS2 f2 + + CSn fn

Where:

n is the number of lashings being calculated

Fy is transverse force from load assumption (kN)

μ is friction coefficient m is mass of the cargo item (t)

g is gravity acceleration of earth = 9.81 m/s2

CS is calculated strength of transverse securing devices (kN)

CS

=

MSL

1.5

 

f is a function of μ and the vertical securing angle α (see table 6).

7.2.4.2 A vertical securing angle α greater than 60 will reduce the effectiveness of this particular securing device in respect to sliding of the item. Disregarding of such devices from the balance of forces should be considered, unless the necessary load is gained by the imminent tendency to tipping or by a reliable pre-tensioning of the securing device and maintaining the pre-tension throughout the voyage.

7.2.4.3 Any horizontal securing angle, i.e. deviation from the transverse direction, should not exceed 30, otherwise an exclusion of this securing device from the transverse sliding balance should be considered.

 

 

Figure 17 - Balance of transverse forces

Table 6 - f values as a function of α and μ

α

μ

-30

-20

-10

0

10

20

30

40

50

60

70

80

90

0.3

0.72

0.84

0.93

1.00

1.04

1.04

1.02

0.96

0.87

0.76

0.62

0.47

0.30

0.1

0.82

0.91

0.97

1.00

1.00

0.97

0.92

0.83

0.72

0.59

0.44

0.27

0.10

0.0

0.87

0.94

0.98

1.00

0.98

0.94

0.87

0.77

0.64

0.50

0.34

0.17

0.00

Remark: f = μ sin α + cos α

7.2.4.4 As an alternative to using table 6 to determine the forces in a securing arrangement, the method outlined in paragraph 7.3 can be used to take account of transverse and longitudinal components of lashing forces.

7.2.5 Transverse tipping

This balance calculation should meet the following condition (see also figure 18):

Fy a ≤ b m g + CS1 c1 + CS2 c2 + + CSn cn

 

where

 

Fy, m, g, CS, n are as explained under 7.2.1

a is lever-arm of tipping (m) (see figure 18)

b is lever-arm of stableness (m) (see figure 18)