1.2 Penetration test procedure

 The penetration test constitutes a procedure whereby a material in a cylindrical vessel is vibrated. The flow moisture point is determined on the basis of the penetration depth of an indicator.

  1.2.1 Scope

• .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 2 g rms ± 10% (g = gravity acceleration) for 6 min. When the penetration depth of a bit put on the surface exceeds 50 mm, it is judged that the sample contains a moisture content 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.

• .4 The room where the samples are tested should be prepared as mentioned in 1.1.3.

  1.2.2 Apparatus (see figure 1.2.2)

• .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 ancillary equipment (see 1.1.2.5 to .8).

• .2 The vibrator (see figure 1.2.2.2), 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 3 g rms or more, and it can be controlled to adjust the acceleration level.

• .3 Dimensions of cylindrical vessels (see figures 1.2.2.3-1 and 1.2.2.3-2) 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.

• .4 Penetration bits (see figure 1.2.2.4) 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.

• .5 A holder (see figure 1.2.2.5) should be made to guide the rod of a bit with minimum friction to the centre of a cylindrical vessel. When two bits are used, they should be positioned in accordance with figure 1.2.2.

• .6 A cylindrical vessel and penetration indicators should be selected in accordance with the nature and condition of the test sample, namely. size of particles and bulk density.

  1.2.3 Procedure

  1.2.3.1 Preparation of the test sample and the vibrating table

• .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 subsamples, namely (A), (B) and (C). The subsample (A) should be immediately weighed and placed in the drying oven to determine the moisture content of the sample “as-received”.

• The subsamples (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 2 g rms ± 10% with a container filled with a sample mounted on the table.

  1.2.3.2 Preliminary flow moisture test

 This test is intended to measure quickly the approximate flow moisture point, using subsample (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 subsample (B) in four distinct stages and tamp after the addition of each layer using a specified tamper. Tamp to a pressure denoted in 1.1.4.1 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.

• .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 2 g rms ± 10% for 6 min. 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 min 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 described in 1.2.3.2.1 to 1.2.3.2.5.

• .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 1.1.4.4.

  • .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 subsamples (B) and (C) and dry at room temperature to reduce the moisture. Then, divide the material into two subsamples (B) and (C), and repeat the preliminary test.

  1.2.3.3 The main flow moisture test

• .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 subsample (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 1.2.3.2. 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 subsample (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 1.1.4.3.