IMSML Website Article 44/2024: Resolution MSC.539(107) - Amendments to the International Maritime Solid Bulk Cargoes (IMSBC) Code (PART 4 of 7), Section 6 - Methods of Determining the Angle of Repose, AND Section 7 - Cargoes which may Liquefy or Undergo Dynamic Separation

Section 6 - Methods of Determining the Angle of Repose

An angle of repose of a non-cohesive solid bulk material shall be measured by a method approved by the appropriate authority as required by 4.1.4 of this Code, see Section 6.1.

Recommended test methods

There are various methods in use to determine the angle of repose for non-cohesive solid bulk materials. Section 6.2 provides that the recommended test methods are as follows:

[1] Tilting box method - This laboratory test method is suitable for non-cohesive granular materials with a grain size not greater than 10 mm. A full description of the equipment and procedure is given in 2.1 of appendix 2 (see Section 6.2.1);

[2] Shipboard test method - In the absence of a tilting box apparatus, an alternative procedure for determining the approximate angle of repose is given in 2.2 of appendix 2 (see Section 6.2.2).

Section 7 - Cargoes which may Liquefy or Undergo Dynamic Separation

Section 7.1 - Introduction

Such cargoes may appear to be in a relatively dry granular state when loaded, and yet may contain sufficient moisture to become fluid or unstable under the stimulus of compaction and the vibration that occurs during a voyage, see Section 7.1.1. A ship’s motion may cause the cargo to shift sufficiently to capsize the vessel, see Section 7.1.2.

How many types of cargo shift are there? Section 7.1.2 identifies two types:

[1] Sliding failure; OR …

[2] Liquefaction consequence.

Note, for [1] above, trimming the cargo in accordance with Section 5 of this Code can prevent sliding failure, see Section 7.1.2.

Can some Group A Cargoes heat spontaneously? Yes, see Section 7.1.3.

Section 7.2 - Condition for Hazards

What happens to Group A Cargoes that my liquefy during a voyage even when they are cohesive and trimmed level? Liquefaction can result in cargo shift (see Section 7.2.1):

[1] The volume of the spaces between the particles reduces as the cargo is compacted owing to the ship’s motion (see Section 7.2.1.1);

[2] The reduction in space between cargo particles causes an increase in water pressure in the space (see Section 7.2.1.2);

[3] The increase in water pressure reduces the friction between cargo particles, resulting in a reduction in the shear strength of the cargo (see Section 7.2.1.3).

Does liquefaction occur when cargo consists of large particles or lumps, and water passes through the spaces between the particles? NO, as there is no increase in water pressure, see Section 7.2.2.

When can a cargo shift cause liquefaction? Generally, when the moisture content exceeds the TML. However some cargoes are susceptible to moisture migration, and may develop a dangerous wet base even if the average moisture content is less than the TML. For cargoes like this, even when the cargo surface is dry, undetected liquefaction may take place, resulting in the shifting of cargo, see Section 7.2.3. Note, that cargoes with high moisture content are prone to sliding, especially when the cargo is shallow and subject to large heel angles.

How do viscous fluid state cargoes behave? It may flow from one side of the ship with a roll, but do not completely return with a roll the other way. Therefore, the ship may progressively reach a dangerous heel and capsize quite suddenly, see Section 7.2.4.

Section 7.3 Provisions for Cargoes which May Liquefy or Undergo Dynamic Separation

Section 7.3.1 - General

When shall Group A Cargoes be accepted for loading? When the actual moisture content of the cargo is less than its TML, see Section 7.3.1.1. For cargoes having moisture content in excess of the TML, may be carried, but with this caveat: It requires specially constructed or fitted cargo ship for confining cargo shift (see Section 7.3.2 below)

Are there restriction in stowage for surrounding cargoes? Cargoes which contains liquids other than packaged canned goods shall not be stowed in the same cargo space above or adjacent to these solid bulk cargoes, see Section 7.3.1.3.

What can be done to prevent liquids entering the cargo space in which these solid bulk cargoes are stowed during the voyage? Section 7.3.1.4 mandates that ‘adequate measures’ are taken, but does not specify in detail what are the exact procedures.

Are there dangers of using water to cool these cargoes while the ship is at sea? Masters should be cautioned about doing this as introducing water may bring the moisture content of these cargoes to a flow state. Where necessary, due consideration shall be given to apply water in the form of spray, see Section 7.3.1.5.

Section 7.3.2 - Specially Constructed or Fitted Cargo Ship for Confining Cargo Shift

Such ships shall have permanent structural boundaries, so arranged as to confine any shift of cargo to an acceptable limit. The ship has to carry evidence of approval by IMO, see Section 7.3.2.1.

If portable divisions are used, Section 7.3.2.2 requires compliance with the following:

[1] Design and position shall provide restraint of the immense forces generated by the flow movement of high-density bulk cargoes. There is a need to reduce to an acceptable level the potential heeling movements arising out of a transverse cargo flow across the cargo space. The divisions shall not be constructed of wood (see Section 7.3.2.2.1);

[2] As necessary, the elements of the ship’s structure bounding such cargo shall be strengthened (see Section 7.3.2.2.2);

[3] Detailed plans of the steadily arrangement and stability arrangements should be approved by IMO. The ship shall carry evidence of this IMO approval (see Section 7.3.2.2.3).

What must be submitted to IMO for such an approval? Section 7.3.2.3 stipulates the following:

[1] Relevant structural drawings (including scaled longitudinal and transverse sections) (see Section 7.3.2.3.1);

[2] Stability calculations (taking into account loading arrangements and possible cargo shift) showing the distribution of cargo and liquids in tanks, and of cargo which may become fluid; AND …

[3] Any other information which may assist IMO in the assessment of the submission.

Section 7.3.3 - Specially Constructed Cargo Ships for Dry Powdery Cargoes

Section 7.3.3.1 requires the following for the construction of the ship:

[1] Constructed to solely carry dry powdery cargoes (see Section 7.3.3.1.1); AND …

[2] Handles cargoes by means of closed type system using pneumatic equipment which prevent the cargo from the exposure to weather (see Section 7.3.3.1.2).

Note, that the ship shall carry evidence of approval by IMO, see section 7.3.3.2.

Thank you for reading IMSML Website Article 44/2024

Stay tuned for the next IMSML Website Article 45/2024: Resolution MSC.539(107) - Amendments to the International Maritime Solid Bulk Cargoes (IMSBC) Code, Section 8 - Test Procedures for Group A Cargoes, AND Section 9 - Materials Possessing Chemical Hazards

Signing-off for today,

Dr Irwin Ooi Ui Joo, LL.B(Hons.)(Glamorgan); LL.M (Cardiff); Ph.D (Cardiff); CMILT

Professor of Maritime and Transport Law

Head of the Centre for Advocacy and Dispute Resolution

Faculty of Law

Universiti Teknologi MARA Shah Alam

Selangor, Malaysia

Tuesday, 3 September 2024

Note that I am the corresponding author for the IMSML Website Articles. My official email address is: uijoo310@uitm.edu.my