5.1 Within the supply transport chain, there are a number of different stresses acting on the cargo. These stresses may be grouped into mechanical and climatic stresses. Mechanical stresses are forces acting on the cargo under specific transport conditions. Climatic stresses are changes of climatic conditions including extremely low or high temperatures.
5.2 During transport various forces will act on the cargo. The force acting on the cargo is the mass of the cargo (m) which is measured in kg or ton, multiplied by the acceleration (a) which is measured in m/s² :
F = m ∙ a
Acceleration considered during transport are the gravitational acceleration (a = g = 9.81 m/s²) and acceleration caused by typical transport conditions such as by the braking or rapid change of traffic lanes by a road vehicle or by the motions of a ship in heavy sea. These accelerations are expressed as product of the gravitational acceleration (g) and a specific acceleration coefficient (c) e.g. a = 0.8 g.
5.3 The following tables provide the applicable acceleration coefficients for the different modes of transport and for the various securing directions. To prevent a cargo from movement, the cargo has to be secured in longitudinal and transverse direction according to the worst combination of horizontal and corresponding vertical accelerations. The securing arrangement has to be designed to withstand the forces due to accelerations in each horizontal direction (longitudinal and transverse) separately (see chapter 9 and annex 7).
Road transport | ||||
Securing in | Acceleration coefficients | |||
Longitudinally (cx) | Transversely | Minimum vertically down | ||
forward | rearward | |||
Longitudinal direction | 0.8 | 0.5 | - | 1.0 |
Transverse direction | - | - | 0.5 | 1.0 |
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Rail transport (combined transport) | ||||
Securing in | Acceleration coefficients | |||
Longitudinally (cx) | Transversely (cy) | Minimum vertically down (cz) | ||
forward | rearward | |||
Longitudinal direction | 0.5 (1.0)† | 0.5 (1.0)† | - | 1.0 (0.7)† |
Transverse direction | - | - | 0.5 | 1.0 (0.7)† |
† The values in brackets apply to shock loads only with short impacts of 150 milliseconds or shorter, and may be used, for example, for the design of packaging. | ||||
Sea transport | |||||
Significant wave height in sea area | Securing in | Acceleration coefficients | |||
Longitudinally | Transversely | Minimum vertically down | |||
A | Hs ≤ 8 m | Longitudinal direction | 0.3 | - | 0.5 |
Transverse direction | - | 0.5 | 1.0 | ||
B | 8 m < Hs ≤ 12 m | Longitudinal direction | 0.3 | - | 0.3 |
Transverse direction | - | 0.7 | 1.0 | ||
C | Hs > 12 m | Longitudinal direction | 0.4 | - | 0.2 |
Transverse direction | - | 0.8 | 1.0 | ||
5.4 The effect of short term impact or vibrations should always be considered. Therefore, whenever the cargo cannot be secured by blocking, lashing is required to prevent the cargo from being significantly displaced, taking into account the characteristics of the cargo and the mode of transport. The mass of the cargo alone, even when combined with a high friction coefficient (see appendix 2 to annex 7), does not sufficiently secure the cargo as the cargo can move due to vibrations.
5.5 The significant 20-years return wave height (Hs) is the average of the highest one-third of waves (measured from trough to crest) that is only exceeded once in 20 years. The allocation of geographic sea areas to the respective significant wave heights is shown in the following table:
A | B | C |
Hs ≤ 8 m | 8 m < Hs ≤ 12 m | Hs > 12 m |
Baltic Sea (incl. Kattegat) Mediterranean Sea Black Sea Red Sea Persian Gulf Coastal or inter-island voyages in following areas: Central Atlantic Ocean Central Indian Ocean Central Pacific Ocean (between 30°N and 35°S) | North Sea Skagerak English Channel Sea of Japan Sea of Okhotsk Coastal or inter-island voyages in following areas: South-Central Atlantic Ocean South-Central Indian Ocean South-Central Pacific Ocean | unrestricted |
Sources: The Royal Netherlands Meteorological Institute (KNMI):
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5.6 During longer voyages, climatic conditions (temperature, humidity) are likely to vary considerably. These may affect the internal conditions in a CTU which may give rise to condensation on cargo or internal surfaces (see annex 3).
5.7 Whenever a specific cargo might be damaged when exposed to high or low temperatures during transport, the use of a CTU specially equipped for keeping the cargo temperature within acceptable limits should be considered (see chapter 7).
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