Flow Table Test

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Flow Table Test Apparatus (Source: http://tmltesting.com).

The Flow Table Test (FTT) is one of the three test methods stated in Appendix 2 of the International Maritime Solid Bulk Cargoes Code (IMSBC Code) used to determine the Transportable Moisture Limit (TML) of Group A or liquefiable solid bulk cargoes. The two other test methods stated in Appendix 2 of the IMSBC Code used to determine the TML of Group A or liquefiable solid bulk cargoes are the Penetration Test (PT) and Proctor/Fagerberg Test (PFT)[1].

Note: All information contained within these boxes were obtained from Appendix 2 of the International Maritime Solid Bulk Cargoes Code, 2013 Edition[1].


Note: All information contained within these boxes are collaborative notes and not specifically recommended in the International Maritime Solid Bulk Cargoes Code, 2013 Edition[1]


Note: Please refer to the latest edition of the International Maritime Solid Bulk Cargoes Code (IMSBC Code) before performing the test described below.


History[edit]

A timeline of events relating to TML Testing. This includes the Penetration Test, Flow Table Test, Proctor/Fagerberg Test and Modified Proctor/Fagerberg Test for iron ore fines. Also included are the International Maritime Solid Bulk Cargoes Code (IMSBC Code) editions[2].

The Flow Table test (FTT) has been widely used in the cement industry to test hydraulic cement since 1983 with the release of ASTM C230 / C230M Standard Specification for Flow Table for Use in Tests of Hydraulic Cement [3]. It can be traced back to 1971 when it was used to test Portland-Cement [4] and as far back as 1952 when it was used to test Magnesium Oxychloride Cements [5]. The early BC Code included a modified procedure, created by the Department of Mines and Technical Services in Canada that can be used to determine the TML of bulk cargoes using the Flow Table apparatus. In 2000, this method also branched out into the ISO Guide 12742 [6] [7]. The FTT was introduced to the IMSBC Code, when it was known as the Code of Safe Practice for Solid Bulk Cargoes (BC Code), between 1970 to 1971 [8].

Timeline[edit]

Year Document Development Reference(s)
1952 ASTM Designation C230 - Standard Specification for Flow Table for Use in Tests of Hydraulic Cement Released [5][7]
1970 to 1971 Code of Safe Practice for Solid Bulk Cargoes (BC Code) Introduced [1][9]
1971 ASTM Designation C124 - Method of Test for Flow of Portland-Cement Concrete by use of the Flow Table Released [4][7]
1983 ASTM C230 / C230M Standard Specification for Flow Table for Use in Tests of Hydraulic Cement Becomes widely used [3][7]
2000 ISO 12742 - Copper, Lead, and Zinc Sulfide Concentrates - Determination of Transportable Moisture Limits - Flow-Table Method Introduced [6][7]
2007 ISO 12742 - Copper, Lead, and Zinc Sulfide Concentrates - Determination of Transportable Moisture Limits - Flow-Table Method Latest Publication [6]
2008 AS 4974 - Copper, Lead, and Zinc Sulfide Concentrates - Determination of Transportable Moisture Limits - Flow-Table Method Introduced (ISO 12742 Equivalent) [10]

Scope[edit]

The flow table is generally suitable for mineral concentrates or other fine material with a maximum grain size of 1 mm. It may also be applicable to materials with a maximum grain size up to 7 mm. It will not be suitable for materials coarser than this and may also not give satisfactory results for some materials with high clay content. If the flow table test is not suitable for the material in question, the procedures to be adopted should be those approved by the authority of the port State.


The test described in Appendix 2 paragraph 1.1 of the IMSBC Code (the FTT) is used to determine the:

  1. moisture content of a sample of cargo,
  2. the Flow Moisture Point (FMP) of the cargo under impact or cyclic forces of the flow table apparatus and
  3. the Transportable Moisture Limit (TML) of the cargo.

Apparatus[edit]

Flow Table mould volume calculations.
Flow Table Test tamper (figure 1.1.2.4 in Appendix 2 of the IMSBC Code, 2013 Edition)
Flow Table Apparatus (figure 2(1) (Partial) in ASTM C230/C230M - 2008)
Flow Table Apparatus (figure 2(2) (Partial) in ASTM C230/C230M - 2008)
Flow Table Apparatus (figure 2(3) (Partial) in ASTM C230/C230M - 2008)
  1. Standard flow table and frame (ASTM Designation (C230-68) - see 3),
  2. Flow table mounting (ASTM Designation (C230-68) - see 3),
  3. Mould (ASTM Designation (C230-68) - see 3),
  4. Tamper (see figure 1.1.2.4): the required tamping pressure may be achieved by using calibrated, spring-loaded tampers (examples are included in figure 1.1.2.4) or some other suitable design of tamper that allows a controlled pressure to be applied via a 30 mm diameter tamper head.
  5. Scales and weights (ASTM Designation (C109-73) - see 3) and suitable sample containers.
  6. Glass graduated measuring cylinder and burette having capacities of 100-200 mL and 10 mL, respectively.
  7. A hemispherical mixing bowl approximately 30 cm diameter, rubber gloves and drying dishes or pans. Alternatively, an automatic mixer of similar capacity can be used for the mixing operations. In this case, care should be exercised to ensure that the use of such a mechanical mixer does not reduce the particle size of consistency of the test material.
  8. A drying oven with controlled temperature up to approximately 110oC. This oven should be without air circulation.

Volume of Flow Table Mould[edit]

As seen in the figure on the right, the volume of the Flow Table Test mould is calculated as 286.66 cm3. Also, by filling the mould with water and by weighing the amount of water in the mould and using the density of water at the temperature it was weighed you can also measure the volume. By using this method the volume of the mould was determined to be 285.29 cm3.

If you want to use the volume of the Flow Table mould for calculations, it is recommended to recalculate the volume using the exact measurements of your mould or fill your mould with water to determine the volume. The volume given above may not be the exact volume of the mould you are using.


Temperature and Humidity[edit]

It is preferable to work in a room where the samples will be protected from excessive temperatures, air currents and humidity variations. All phases of the material preparation and testing procedure should be accomplished in a reasonable space of time to minimize moisture losses and, in any event, within the day of commencement. Where possible, sample containers should be covered with plastic film or other suitable cover.


Procedure[edit]

The quantity of material required for a flow moisture test will vary according to the specific gravity of the material to be tested. It will range from approximately 2 kg for coal to 3 kg for mineral concentrates. It should be collected as a representative sample of the cargo being shipped. Experience has shown that more accurate test results will be obtained by ensuring that the moisture content of the test sample is increased rather than decreased towards the FMP.

Consequently, it is recommended that a preliminary flow moisture test should be conducted, generally in accordance with the following, to indicate the condition of the test sample, i.e. the quantity of water and the rate at which it is to be added or whether the sample should be air-dried to reduce its moisture content before commencing the main flow moisture test.


Preparation of Test Sample[edit]

The representative sample of test material is placed in the mixing bowl and thoroughly mixed. Three subsamples (A), (B) and (C) are removed from the mixing bowl as follows: about one fifth of the sample (A) should be immediately weighed and placed in the drying oven to determine the moisture content of the sample “as received”. Two further subsamples, each of about two fifths of the gross weight, should then be taken, one (B) for the preliminary FMP test and the other (C) for the main FMP determination:

Filling the mould. The mould is placed on the centre of the flow table and filled in three stages with the material from the mixing bowl. The first charge, after tamping, should aim to fill the mould to approximately one third of its depth. The quantity of sample required to achieve this will vary from one material to another, but can readily be established after some experience has been gained of the packing characteristics of the material being tested.

The second charge, after tamping, should fill the mould to about two thirds of its depth and the third and final charge, after tamping, should reach to just below the top of the mould.

Tamping procedure. The aim of tamping is to attain a degree of compaction similar to that prevailing at the bottom of a shipboard cargo of the material being tested. The correct pressure to be applied is calculated from:

Tamping pressure (Pa) = Bulk density of cargo (kg/m3) x Maximum depth of cargo (m) x Gravity acceleration (m/s2)

You can also use the calculator provided on the main site by clicking the following link:

http://tmltesting.com/calc-tamping.php


Bulk density can be measured by a single test, using the Proctor C apparatus described in ASTM Standard D-698 or JIS-A-1210, on a sample of the cargo at the proposed moisture content of loading.

When calculating the tamping pressure, if no information concerning cargo depth is available the maximum likely depth should be used.

Alternatively, the pressure may be estimated from the table below:


Typical Cargo Bulk Density
(kg/m3)
Maximum Cargo Depth
(m)
Tamping Pressure
(kPa)
Force on 30 mm Diameter Head
(kgf)
Coal 1,000 2 20 1.4
Coal 1,000 5 50 3.5
Coal 1,000 10 100 7.1
Coal 1,000 20 200 14.1
Coal 2,000 2 40 2.8
Coal 2,000 5 100 7.1
Coal 2,000 10 200 14.1
Coal 2,000 20 400 28.3
Metal Ore 3,000 2 60 4.2
Metal Ore 3,000 5 150 10.6
Metal Ore 3,000 10 300 21.2
Metal Ore 3,000 20 600 42.4
Iron Ore Concentrate 4,000 2 80 5.7
Iron Ore Concentrate 4,000 5 200 14.1
Iron Ore Concentrate 4,000 10 400 28.3
Iron Ore Concentrate 4,000 20 800 56.5
Lead Ore Concentrate 5,000 2 100 7.1
Lead Ore Concentrate 5,000 5 250 17.7
Lead Ore Concentrate 5,000 10 500 35.3
Lead Ore Concentrate 5,000 20 1,000 70.7

Tampingpressure.png

Note: Extrapolation of the tamping pressure from the graph above is not part of the procedure stated in Appendix 2 of the IMSBC Code, 2013 Edition. The graph is shown just as a visual guide to the data given in the table above.

The number of tamping actions (applying the correct, steady pressure each time) should be about 35 for the bottom layer, 25 for the middle and 20 for the top layer, tamping successively over the area completely to the edges of the sample to achieve a uniformly flat surface for each layer.

Removal of the mould. The mould is tapped on its side until it becomes loose, leaving the sample in the shape of a truncated cone on the table.


Preliminary Flow Moisture Test[edit]

Preliminary Flow Table Test (figure 1.1.4-1 in Appendix 2 of the IMSBC Code, 2013 Edition)
Stages of Flow Table Testing on a sample of Iron Ore Fines. See : Identification of a Flow State.

Immediately after removing the mould, the flow table is raised and dropped up to 50 times through a height of 12.5 mm at a rate of 25 times per minute. If the material is below the FMP, it usually crumbles and bumps off in fragments with successive drops of the table.

At this stage, the flow table is stopped and the material returned to the mixing bowl, where 5-10 ml of water, or possibly more, is sprinkled over the surface and thoroughly mixed into the material, either with rubber-gloved fingers or an automatic mixer.

The mould is again filled and the flow table is operated as described above for up to 50 drops. If a flow state is not developed, the process is repeated with further additions of water until a flow state has been reached.

Identification of a flow state. The impacting action of the flow table causes the grains to rearrange themselves to produce compaction of the mass. As a result, the fixed volume of moisture contained in the material at any given level increases as a percentage of the total volume. A flow state is considered to have been reached when the moisture content and compaction of the sample produce a level of saturation such that plastic deformation occurs (In certain conditions, the diameter of the cone may increase before the flow moisture point is reached, due to low friction between the grains rather than to plastic flow. This must not be mistaken for a flow state.). At this stage, the moulded sides of the sample may deform, giving a convex or concave profile.

With repeated action of the flow table, the sample continues to slump and to flow outwards. In certain materials, cracks may also develop on the top surface. Cracking, with the appearance of free moisture, is not, however, an indication of development of a flow state. In most cases, measurement of the deformation is helpful in deciding whether or not plastic flow has occurred. A template which, for example, will indicate an increase in diameter of up to 3 mm in any part of the cone is a useful guide for this purpose. Some additional observations may be useful. For example: when the (increasing) moisture content is approaching the FMP, the sample cone begins to show a tendency to stick to the mould. Further, when the sample is pushed off the table, the sample may leave tracks (stripes) of moisture on the table. If such stripes are seen, the moisture content may be above the FMP: the absence of tracks (stripes) is not necessarily an indication of being below the FMP.

Measuring the diameter of the cone, at the base or at half height, will always be useful. By addition of water in increments of 0.4% to 0.5% and applying 25 drops of the flow table, the first diameter increase will generally be between 1 and 5 mm and after a further increment of water the base diameter will have expanded by between 5 and 10 mm.

As an alternative to the procedure described above, for many concentrates a fast way of finding the approximate FMP is as follows:

When the moisture content is definitely beyond the FMP, measure the diameter after 25 drops, repeat the test after adding a further increment of water, measure the diameter and draw a diagram as illustrated in figure 1.1.4-1, showing increase in diameter plotted against moisture content. A straight line drawn through the two points will cross the moisture content axis close to the FMP.

Having completed the preliminary FMP test, the sample for the main test is adjusted to the required level of moisture content (about 1% to 2%) below the flow point.


During the Flow Table Test, the FMP is said to be reached when the sample has reached the flow state. The term flow state, in regards to the Flow Table Test, refers to when a sample is showing plastic deformation. This is not to be confusing with showing 'flow'.

See Also: Identification of a Flow State


Main Flow Moisture Test[edit]

When a flow state has been reached in the preliminary test, the moisture content of sub-sample (C) is adjusted to about 1% to 2% less than the last value which did not cause flow in the preliminary test (this is suggested simply to avoid starting the main test too close to the FMP and then having to waste time air-drying it and starting again). The final test is then carried out on this adjusted sample in the same manner as for the preliminary test, but in this case with the addition of water in increments of no more than 0.5% of the mass of the test material (the lower the “preliminary” FMP, the smaller the increments should be). After each stage, the whole moulded sample should be placed in a container, weighed immediately and retained for moisture determination if required. This will be necessary if the sample flowed or if the next, slightly wetter, sample flows. If not required it may be returned to the mixing bowl.

When a flow state has been reached, the moisture content should be determined on two samples, one with moisture content just above the FMP and the other with moisture content just below the FMP. The difference between the two values should then be 0.5% or less, and the FMP is taken as the mean of these two values.


Calculations[edit]

Note: The TML is determined and reported in gross water content by weight. This is different to net water content by weight.

Introduction[edit]

It should be noted that, for many materials, there are recognized international and national methods for determining moisture content. These methods, or ones that have been established to give equivalent results, should be followed.


Concerntrates and Similar Materials[edit]

It is clearly important that the samples should be dried to a constant mass. In practice, this is ascertained after a suitable drying period at 105oC by weighing the sample successively with an interval of several hours elapsing. If the mass remains constant, drying has been completed, whereas if the mass is still decreasing, drying should be continued.

The length of the drying period depends upon many variables, such as the disposition of the material in the oven, the type of container used, the particle size, the rate of heat transfer, etc. It may be that a period of five hours is ample for one concentrate sample, whereas it is not sufficient for another. Sulphide concentrates tend to oxidize, and therefore the use of drying ovens with air circulation systems is not recommended for these materials, nor should the test sample be left in the drying oven for more than four hours.


Coal[edit]

The recommended methods for determination of the moisture content are those described in ISO 589-1974, “Hard Coal – Determination of Total Moisture”. This method, or ones that have been established to give equivalent results, should be followed.


Calculation of moisture content, FMP and transportable moisture limit:

The moisture content (specifically the gross water content by weight) of the concentrate "as received" is:

Fttcalc12016.png

Where:

w1 = Gross Water Content (%),
m1 = the exact mass of the subsample "as received" and
m2 = the exact mass of the "as received" subsample, after drying.

The Flow Moisture Point (FMP) of the material is (in gross water content by weight):

Fttfmp.gif

Where:

FMP = Flow Moisture Point (%),
m3 = the exact mass of the sample just above the flow state,
m4 = the exact mass of the sample just above the flow state, after drying,
m5 = the exact mass of the sample just below the flow state and
m6 = the exact mass of the sample just below the flow state, after drying.

The Transportable Moisture Limit (TML) of the material is (in gross water content by weight):

Ftttmlorig.gif

Where:

TML = Transportable Moisture Limit (%) and
FMP = Flow Moisture Point (%).

Peat Moss[edit]

For all Peat Moss, determine the bulk density, using either the ASTM or CEN (20 litres) method.

Peat should be above or below 90kg/cubic meter on a dry weight basis in order to obtain the correct TML.

As indicated in 1.1.1, the following should be determined:

  1. the moisture content of a sample of cargo (MC);
  2. the flow moisture point (FMP);
  3. the transportable moisture limit (TML). The TML will be determined as follows:
    1. for peat with a bulk density of greater than 90 kg/cubic metre on a dry weight is 85% of the FMP; and
    2. for peat with a bulk density of 90 kg/cubic metre or less on a dry weight, the TML is 90% of the FMP.

Typical Values[edit]

Below are some typical Transportable Moisture Limit (TML) and Flow Moisture Point (FMP) values, determined using the Flow Table Test, for common solid bulk cargoes:

Material Typical FMP values determined using the Flow Table Test (% GWC) Typical TML values determined using the Flow Table Test (% GWC)
Iron Ore Fines 8.22 - 13.67 (Average = 10.48)[7] 7.40 - 12.30 (Average = 9.43)[7]

Discussion[edit]

To discuss the information on this page you can click on the discussion tab at the top left of this page or use the 'Disqus' option at the bottom of this page.

References[edit]

  1. 1.0 1.1 1.2 1.3 International Maritime Organisation, International Maritime Solid Bulk Cargoes Code, 2013 Edition, London: International Maritime Organization.
  2. Munro, M., & Mohajerani, A. (2016). Moisture Content Limits of Iron Ore Fines to Prevent Liquefaction During Transport: Review and Experimental Study. International Journal of Mineral Processing, 148. doi: http://dx.doi.org/10.1016/j.minpro.2016.01.019
  3. 3.0 3.1 American Society for Testing and Materials, ASTM Designation C230 / C230M - Standard Specification for Flow Table for Use in Tests of Hydraulic Cement. 2008.
  4. 4.0 4.1 American Society for Testing and Materials, ASTM Designation C124 - Method of Test for Flow of Portland-Cement Concrete by use of the Flow Table. 1971.
  5. 5.0 5.1 American Society for Testing and Materials. ASTM Designation C230 - Standard Specification for Flow Table for Use in Tests of Hydraulic Cement. 1952 [cited 2015; Available from: http://www.standardscatalog.com/catalog/show/ASTM-C230/history/.
  6. 6.0 6.1 6.2 International Standards Organization, ISO 12742 - Copper, Lead, and Zinc Sulfide Concentrates - Determination of Transportable Moisture Limits - Flow-Table Method. 2007.
  7. 7.0 7.1 7.2 7.3 7.4 7.5 7.6 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.
  8. Munro, M. and A. Mohajerani, Moisture Content Limits of Iron Ore Fines to Prevent Liquefaction During Transportation. International Journal of Mineral Processing.
  9. Munro, M. and A. Mohajerani, Moisture Content Limits of Iron Ore Fines to Prevent Liquefaction During Transportation. International Journal of Mineral Processing.
  10. Australian Standards, AS 4974 - Copper, Lead, and Zinc Sulfide Concentrates - Determination of Transportable Moisture Limits - Flow-Table Method. 2008.

See Also[edit]

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