Transportable Moisture Limit

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The Transportable Moisture Limit (TML) is the maximum Gross Water Content (GWC) by weight that a Group A or liquefiable solid bulk cargo may contain while being transported on a bulk carrier without it being at risk of liquefying. The TML is determined using one of three methods stated in Appendix 2 of the International Maritime Solid Bulk Cargoes Code (IMSBC Code)[1] or, as in the case for Iron Ore Fines (IOF) and Coal, the modified method as stated in DSC.1/Circ.71[2] and Modified Proctor/Fagerberg Method for Coal[3], respectively. The modified method specifically designed for IOF can be implemented on a voluntarily basis by the relevant authority and is to be amended in the 2015 Edition of the IMSBC Code and to become mandatory as of 1 January 2017[2].

The TML test methods are the:

  1. Flow Table Test,
  2. Proctor/Fagerberg Test,
  3. Penetration Test,
  4. Modified Proctor/Fagerberg Test for Iron Ore Fines and
  5. Modified Proctor/Fagerberg Test for Coal.


Flow Table Test (FTT)

During the Flow Table Test procedure described in Appendix 2 of the International Maritime Solid Bulk Cargoes Code (IMSBC Code), the TML is calculated as 90% of the Flow Moisture Point (FMP). The FMP is calculated as the average gross water content by weight of the two samples on the flow table, one which shows plastic deformation (above FMP) and one which does not show plastic deformation (below FMP). These two samples must have a maximum difference of 0.5% gross water content by weight to be valid.

See: Flow Table Test

Equation

The following equation is derived from the equations given in Appendix 2 of the International Maritime Solid Bulk Cargoes Code (IMSBC Code) which are used to calculate the TML during the Flow Table Test:

Ftttml.gif

Where:

TML = Transportable Moisture Limit (%),
m1 = mass of wet sample just above the Flow Moisture Point (FMP),
m2 = mass of dry sample just above the Flow Moisture Point (FMP),
m3 = mass of wet sample just below the Flow Moisture Point (FMP) and
m4 = mass of dry sample just below the Flow Moisture Point (FMP).

Penetration Test (PT)

During the Penetration Test procedure described in Appendix 2 of the International Maritime Solid Bulk Cargoes Code (IMSBC Code), the TML is calculated as 90% of the Flow Moisture Point (FMP). The FMP is calculated as the average gross water content by weight of the two samples in the Penetration Test mould, one which shows penetration by the penetration bit greater than 50mm (above FMP) and one which does not show penetration by the penetration bit greater than 50mm (below FMP). These two samples must have a maximum difference of 0.5% gross water content by weight to be valid.

See: Penetration Test

Equation

The same equation that is used to determine the TML during the Flow Table Test is used during the Penetration Test.

Proctor/Fagerberg Test (PFT)

Graphical representation of a compaction curve produced by performing a Proctor/Fagerberg Test (PFT) on a solid bulk cargo. Source: http://TMLTesting.com

The Proctor/Fagerberg Test procedure described in Appendix 2 of the International Maritime Solid Bulk Cargoes Code (IMSBC Code) states the TML is equal to the Critical Moisture Content. The Critical Moisture Content (CMC) is the point at which a graphical representation of the compaction curve of a solid bulk cargo, produced while performing the Proctor/Fagerberg Test (PFT), intersects the degree of saturation line equal to 70%.

See: Proctor/Fagerberg Test

Modified Proctor/Fagerberg Test (MPFT)

Iron Ore Fines

The Modified Proctor/Fagerberg Test procedure described in DSC.1/Circ.71 states the TML is equal to the Critical Moisture Content. The Critical Moisture Content (CMC) is the point at which a graphical representation of the compaction curve, produced while performing the Modified Proctor/Fagerberg Test (MPFT) for Iron Ore Fines (IOF), intersects the degree of saturation line equal to 80%.[2]

See: Modified Proctor/Fagerberg Test for Iron Ore Fines

Coal

The Modified Proctor/Fagerberg Test procedure described in the 'Modified Proctor/Fagerberg Method for Coal' states the TML is equal to the Critical Moisture Content. The Critical Moisture Content (CMC) is the point at which a graphical representation of the compaction curve, produced while performing the Modified Proctor/Fagerberg Test for Coal, intersects the degree of saturation line equal to 70%.[3]

See: Modified Proctor/Fagerberg Test for Coal

Other TML Test Methods

Other TML test methods that have been used to determine the TML of a solid bulk cargo, but not mentioned in the IMSBC Code, are tests such as the vibrating platform method, developed by British Coal[4], a drainage method, produced by Norway[5], and a method using a concrete tester developed in Finland[6][7].

References

  1. International Maritime Organisation, International Maritime Solid Bulk Cargoes Code, 2013 Edition, London: International Maritime Organization.
  2. 2.0 2.1 2.2 International Maritime Organisation, DSC.1/Circ.71 - Early Implementation of Draft Amendments to the IMSBC Code Related to the Carriage and Testing of Iron Ore Fines, 15 November 2013, London. (Download PDF)
  3. 3.0 3.1 Modified Proctor/Fagerberg Method for Coal, 24 November 2014. (Download PDF)
  4. Kruszewski, A., When Cargoes Start to Flow. Hazardous Cargo Bulletin, 1989: p. 40.
  5. International Maritime Organization, Development of New Criteria in Respect of Liquefaction and Sliding Failure - Drainage Method for Determination of the Transportable Moisture Limit (BC 26/5/14). 1984.
  6. Sandvik, K. and A. Rein, Safe Transport at Sea of Bulk Mineral Cargoes. Bulk Solids Handling, 1992. 12(5): p. 79–83.
  7. Munro, M. and A. Mohajerani, Determination of Transportable Moisture Limit of Iron Ore Fines for the Prevention of Liquefaction in Bulk Carriers. Marine Structures, 2015. 40(1): p. 193-224.

See Also