Circular Letter MSC/Circ.1026 

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

(adopted on 21 May 2002)

 

1. The Maritime Safety Committee, at its seventy-fifth session (15 to 24 May 2002), approved amendments to the Code of Safe Practice for Cargo Stowage and Securing (CSS Code), as devel­oped by the DSC Sub-Committee at its sixth session (16 to 20 July 2001) and set out in the Annex.

 

2. Member Governments are invited to bring the amendments to the attention of shipowners, ship operators, shipmasters 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 NON-STANDARDIZED CARGO

 

1. SCOPE OF APPLICATION

 

1. In paragraph 1, after the second sentence a new sentence is added as follows:

 

"A11 lashing assemblies used in the application of the meth­ods described in this Annex must be attached to fixed securing points or strong supporting structures marked on the cargo unit or advised as being suitable, or taken as a loop around the unit with both ends secured to the same side as shown in Annex 5, Figure 2 of the Code. Lashings going over the top of the cargo unit, which have no defined secur­ing direction but only act to increase friction by their pretension, cannot be credited in the evaluation of secur­ing arrangements under this Annex."

 

4. STRENGTH OF SECURING EQUIPMENT

 

2. In paragraph 4.2, the second sentence in the first sub-pa­ragraph is replaced by the following text:

 

"Safe Working Load (SWL) may be substituted for MSL for securing purposes, provided this is equal to or exceeds the strength defined by MSL."

 

3. In Table 1 (as amended by MSC/Circ.812), "70% of break­ing strength" on the line regarding web lashing is replaced by "50% of breaking strength".

 

5. SAFETY FACTOR

 

4. Existing paragraph 5 is replaced by the following text and re-numbered as paragraph 6:

 

"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.

 

CS = MSL/safety factor

 

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. RULE-OF-THUMB METHOD

 

5. Existing paragraph 6 is re-numbered as paragraph 5. Existing sub-paragraphs 6.1, 6.2 and 6.3 are re-numbered as 5.1, 5.2 and 5.3 accordingly.

 

7. ADVANCED CALCULATION METHOD

 

6. After Table 3 the following text and formula are added:

 

"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 shall not be used for ship lengths less than 50 m or more than 300 m."

 

7. Under the existing paragraph 7.2, the following text and a new table are added:

 

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

 

Table 5
Friction coefficients

 

 

 

8. In paragraph 7.2.1, the text from (µ = 0.3 for steel-timber or steel- rubber) to (µ = 0.0 for steel-steel, wet) is deleted; "table 5" in the definition of "f" is replaced by "table 6"; and a for­mula is added under the definition of CS as follows:

 

 

9. Existing Table 5 is re-numbered as Table 6.

 

10. Under the re-numbered Table 6, the following text is added:

 

"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."

 

11. In paragraph 7.2.3, under the definition of CS a formula is added:

 

 

12. A new paragraph 7.2.4 is added as follows:

 

"7.2.4 Calculated example

 

A calculated example for this method is shown in Appen­dix l."

 

13. A new paragraph 7.3 is added as follows:

 

"7.3 Balance of forces - alternative method

 

The balance of forces described in paragraph 7.2.1 and 7.2.3 will normally furnish a sufficiently accurate determination of the adequacy of the securing arrangement. However, this alter­native method allows a more precise consideration of horizontal securing angles.

 

Securing devices usually do not have a pure longitudinal or transverse direction in practice but have an angle β in the hori­zontal plane. This horizontal securing angle β is defined in this Annex as the angle of deviation from the transverse direction. The angle β is to be scaled in the quadrantal mode, i.e. between 0 and 90°.

 

 

Figure 3
- Definition of the vertical and horizontal securing angles α and β

 

A securing device with an angle β develops securing effects both in longitudinal and transverse direction, which can be ex­pressed by multiplying the calculated strength CS with the ap­propriate values of F_x or F_y. The values of F_x and F_y can be ob­tained from Table 7.

 

Table 7 consists of five sets of figures, one each for the fric­tion coefficients µ = 0.4, 0.3, 0.2, 0.1 and 0. Each set of figures is obtained by using the vertical angle α and horizontal angle β. The value of F_x is obtained when entering the table with β from the right while F_y is obtained when entering with β from the left, using the nearest tabular value for α and β. Interpolation is not required but may be used.

 

The balance calculations are made in accordance with the following formulae:

 

Transverse sliding:

 

F_y ≤ µmg+F_y1CS₁+...F_ynCS_n

 

 

Longitudinal sliding:

F_x ≤ µ(mg - F₂) + F_x1CS_l+F_xnCS_n

 

 

Transverse tipping:

 

F_ya ≤ bmg + 0.9(CS₁с₁ + CS₂с₂ +... + СS_nс_n)

 

Caution:

 

Securing devices, which have a vertical angle a of less than 45° in combination with horizontal angle β greater than 45°, should not be used in the balance of transverse tipping in the above formula.

 

All symbols used in these formulae have the same meaning as defined in paragraph 7.2 except F_y and F_x, obtained from Ta­ble 7, and CS is as follows:

 

 

A calculated example for this method is shown in Appen­dix 1.

 

Table 7
- F_x-values and F_y - values as a function of α, β and µ

 

Table 7.1 for µ = 0.4

 

 

Table 7.2 for µ = 0.3

 

 

 

Table 7.3 for µ = 0.2

 

 

Table 7.4 for µ = 0.1

 

 

 

Table 7.5 for µ = 0.0

 

 

Remark: F_x = cos α sin β + µ sin α. F_y = cos α cos β + µ sin α

 

14. The existing text under the heading "Advanced calculation method: calculated example" with the heading are deleted from section 7 and added in as new Appendix 1 to the Annex with modifications as following paragraphs 15 and 16.

 

15. In new Appendix 1, the words "Advanced calculation method: calculated example" are replaced by the follows:

 

"Calculated example 1

(refer to paragraph 7.2,
Balance of forces and moments)"

 

16. In new Appendix 1, calculated example 2 is added after cal­culated example 1 as follows:

 

"Calculated example 2

(refer to paragraph 7.3,
Balance of forces - alternative method)

 

A cargo unit of 68 t mass is stowed on timber (µ = 0.3) in the tween deck at 0.7L of a vessel. L = 160 m, B = 24 m, ν = = 18 kn and GM = 1.5 m. Dimensions of the cargo unit are height = 2.4 m and width = 1.8 m. The external forces are: F_x = = 112 kN, F_y = 312 kN, F_z = 346 kN.

 

The top view shows the overall securing arrangement with eight lashings.