Penetration Test

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Penetration Test Apparatus (Modified Image from: http://geo-con.com.au)[1]
Penetration Bits and Holder (Modified Image from: http://geo-con.com.au)[1]

The Penetration Test (PT) 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 Flow Table Test (FTT) and Proctor/Fagerberg Test (PFT). The PT constitutes a procedure whereby a material in a cylindrical vessel is vibrated. The Flow Moisture Point (FMP) is determined on the basis of the penetration depth of an indicator.[2].

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


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[3].

The Penetration test was developed in Japan by Tamaki Ura and Masato Tanaka at the Research Institute of Marine Engineering for determining the TML of coal [4]. Research began on the Penetration test in 1989 [4] and it was adopted by the International Maritime Organization, in 1994, for determining the TML of ore concentrates and coal [5][6].

Timeline[edit]

Year Document Development Reference(s)
1987 Analysis of Capsizing of Bulk Carrier due to Liquefaction of Ore Concentrates with Height Moisture Content Published [7]
1988 Determination of flow moisture point Published [8]
1988 Study on the Liquefaction Characteristics of Coal Published [9]
1989 Development of Test Method of Transportable Moisture Limit for Coals Published [10]
1989 Development of The Penetration Method for Mineral Concentrates Published [4]
1990 Development of new criteria against shifting of bulk cargoes Published [11]
1990 Tentative results of international co-operation experiment on the penetration method Published [12]
1990 Supplementary data for determining the conditions of the penetration method for mineral concentrates and similar materials Published [13]
1991 Development of a Test Method to determine Flow Moisture Point of Bulk Cargo Published [14]
1994 Code of Safe Practice for Solid Bulk Cargoes (BC Code) Introduced [5][6]

Scope[edit]

  1. The penetration test is generally suitable for mineral concentrates, similar materials, and coals up to a top size of 25 mm.
  2. In this procedure, the sample, in a cylindrical vessel, is subjected to vertical vibration of 2g rms + 10% (g = gravity acceleration) for 6 minutes. When the penetration depth of a bit put on the surface exceeds 50 mm, it is judged that the sample contains a moisture greater than the flow moisture point.
  3. This procedure consists of a preliminary test to get an approximate value of the flow moisture point and a main test to determine the accurate flow moisture point. When the approximate value of the flow moisture point is known, the preliminary test can be omitted.

The test described in Appendix 2 paragraph 1.2 of the IMSBC Code (the PT) is used to determine the:

  1. moisture content of a sample of cargo,
  2. the Flow Moisture Point (FMP) of the cargo and
  3. the Transportable Moisture Limit (TML) of the cargo.

Apparatus[edit]

Penetration Test tamper (figure 1.1.2.4 in Appendix 2 of the IMSBC Code, 2013 Edition)
  1. The test apparatus consists of:
    1. a vibrating table;
    2. cylindrical vessels;
    3. indicators (penetration bits and a holder);
    4. a tamper (see 1.1.2.4); and
    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.
  2. The vibrator, with a table on which a cylindrical vessel can be clamped, should be capable of exciting a mass of 30 kg at a frequency of either 50 Hz or 60 Hz with an acceleration of 3g rms or more, and it can be controlled to adjust the acceleration level.
  3. Penetration bits are made of brass. The mass of the bit for coal should be adjusted to 88 g (5 kPa), and that for concentrates to 177 g (10 kPa). When the sample contains coarse particles, it is recommended that two bits of the same pressure are put on the surface to avoid misjudgment.
  4. A holder should be made to guide the rod of a bit with minimum friction to the centre of a cylindrical vessel.
  5. A cylindrical vessel and penetration indicators should be selected in accordance with the nature and condition of the test sample, viz. size of particles and bulk density.
  6. Dimensions of cylindrical vessels are as follows:

Cylinder size Inner diameter Depth Wall thickness
small 146 mm 202 mm 9.6 mm or more
large 194 mm 252 mm 10.3 mm or more
The vessels should be made of reasonably rigid, non-magnetic, impermeable and lightweight material such as acrylics or vinyl chloride.
The small cylindrical vessel is selected for the materials having a maximum particle size of 10 mm or less. The large cylindrical vessel is for those having a maximum particle size of 25 mm or less.

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 test material required 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]

  1. The quantity of the sample required is approximately six times or more the capacity of the selected cylindrical vessel. The amount of representative test sample with which each container is filled should be as follows: approximately 1,700 cm3 for the small container, and 4,700 cm3 for the large container.
  2. Mix the sample well and divide into three approximately equal sub-samples, namely (A), (B) and (C). The sub-sample (A) should be immediately weighed and placed in the drying oven to determine the moisture content of the sample “as received”. The sub-samples (B) and (C) are used for the preliminary test and the main test, respectively.
  3. The vibration level of the vibrating table should be calibrated, using an acceleration meter, prior to carrying out testing. The acceleration of the table should be adjusted to 2g rms + 10% with a container filled with a sample mounted on the table.

Preliminary Flow Moisture Test[edit]

This test is intended to measure quickly the approximate flow moisture point, using sub-sample (B). Water is added in increments after every penetration test. When a flow state has been reached, the moisture content of the sample just above the flow state is measured. The moisture content of the sample just below the flow state can be calculated by deducting the increment of water last added from the gross mass of the sample.

1. Fill the appropriate cylindrical vessel with sub-sample (B) in four distinct stages and tamp after the addition of each layer using a specified tamper. Tamp to a pressure denoted in the Flow Table Test (FTT) procedure (See Below) for mineral concentrates or to 40 kPa for coals, and apply the pressure evenly over the whole surface area of the material until a uniformly flat surface is obtained.


It is noted that “tamping does not affect the result of the Penetration Test, because the sample is quickly consolidated by vibration from the vibrating table regardless of the pressure of tamping conducted prior to the test” [4].

The following is from paragraph 1.1.4.1 (Flow Table Test procedure) of the IMSBC Code, 2013 Edition used to calculate the tamping pressure during the Penetration Test (PT):

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.

After the tamping pressure has been calculated and the tamping procedure performed:

2. Place the penetration bit on the surface of the material through the holder.

3. Operate the vibrator at a frequency of 50 Hz or 60 Hz with an acceleration of 2g rms + 10% for 6 minutes. If necessary, the acceleration level should be checked by referring to the output of the acceleration meter attached to the vibrating table.

4. After 6 minutes of vibration, read the depth of penetration.

5. When the depth of penetration is less than 50 mm, it is judged that liquefaction did not take place. Then:

1. Remove the material from the cylindrical vessel and replace in the mixing bowl with the remainder of the sample.
2. Mix well and weigh the contents of the mixing bowl.
3. Sprinkle an increment of water of not more than 1% of the mass of the material in the bowl and mix well.
4. Repeat the procedure.

6. When the depth of penetration is greater than 50 mm, it is judged that liquefaction took place. Then:

1. Remove the material from the cylindrical vessel and replace in the mixing bowl.
2. Measure the moisture content in accordance with the procedure described in the Flow Table Test (FTT) procedure (also described below).
3. Calculate the moisture content of the sample just below the flow moisture point on the basis of the amount of water added.

7. If the penetration depth in the first attempt exceeds 50 mm, i.e. the sample as received liquefied, mix sub-samples (B) and (C) and dry at room temperature to reduce the moisture. Then, divide the material into two sub-samples (B) and (C), and repeat the preliminary test.


Main Flow Moisture Test[edit]

  1. On the basis of the preliminary test, the main test should be carried out to determine the flow moisture point more accurately.
  2. Adjust the moisture content of the sub-sample (C) to the last value, which did not cause flow in the preliminary flow moisture test.
  3. The first test of the main flow moisture test is carried out on this adjusted sample in the same manner as described in the preliminary test, In this case, however, the addition of water in increments should not be more than 0.5% of the mass of the test material.
  4. When the approximate value of the flow moisture point is known in advance, the moisture content of the sub-sample (C) is adjusted to approximately 90% of this value.
  5. When a flow state has been reached, the flow moisture point is determined as described in the Flow Table Test (FTT) procedure (also described below).

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) values, determined using the Penetration Test, for common solid bulk cargoes:

Material Typical TML values determined using the Penetration Test (% GWC)
Iron Ore Fines 5.90 - 11.50 (Average = 7.55)[15]

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 Munro, M. and A. Mohajerani, 2015, Management of Hazardous Effects of Liquefaction of Iron Ore Fines during Transportation in Bulk Carriers, Journal of Environmental Management
  2. 2.0 2.1 International Maritime Organisation, International Maritime Solid Bulk Cargoes Code, 2013 Edition, London: International Maritime Organization.
  3. 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
  4. 4.0 4.1 4.2 4.3 Tanaka, M. and T. Ura, Development of The Penetration Method for Mineral Concentrates. International Maritime Organization, Sub-Committee on Dangerous Goods, Solid Cargoes and Containers, BC 30/5/12, 1989
  5. 5.0 5.1 IMO: Code of Safe Practice for Solid Bulk Cargoes (BC Code), IMO, 1994 edition
  6. 6.0 6.1 http://underwater.iis.u-tokyo.ac.jp/research/bulk/bulk-chp3-e.html
  7. URA, Tamaki, Analysis of Capsizing of Bulk Carrier due to Liquefaction of Ore Concentrates with Height Moisture Content, IMO, BC28/INF.4, (1987.1), pp.1-25.
  8. TANAKA, Masato; URA, Tamaki, Determination of flow moisture point, IMO, BC29/5/11, (1988.5).
  9. URA, Tamaki, Study on the Liquefaction Characteristics of Coal, IMO, BC30/5/2, (1988.8).
  10. TANAKA, Masato; URA, Tamaki, Development of Test Method of Transportable Moisture Limit for Coals, Journal of Japan Institute of Navigation, No.80, (1989.3), pp.125-131.
  11. URA, Tamaki; TANAKA, Masato, Development of new criteria against shifting of bulk cargoes, IMO, BC31/3/2, (1990.10).
  12. URA, Tamaki; TANAKA, Masato, Tentative results of international co-operation experiment on the penetration method, IMO, BC31/INF.4, (1990.12).
  13. URA, Tamaki; TANAKA, Masato, Supplementary data for determining the conditions of the penetration method for mineral concentrates and similar materials, IMO, BC31/INF.5, (1990.12).
  14. URA, Tamaki; TANAKA, Masato, Development of a Test Method to determine Flow Moisture Point of Bulk Cargo, Journal of Japan Institute of Navigation, No.84, (1991.3), pp.45-51. (Download PDF)
  15. 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[edit]

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