The methods for manual sampling are applicable to the taking of samples of sponge iron from conveyors, trucks and stockpiles, during the loading or production.
- Identify the lot to be sampled,
- Ascertain the nominal lot size,
- Determine the mass of increment considering the nominal lot size.
The mass of each increment shall be as per the lot quantity to be sampled.
| Sample size | Increments |
| Up to 500Mt | 6 |
| 500 to 1000Mt | 10 |
| 1000 to 2000Mt | 15 |
| 2000 to 5000Mt | 20 |
(While taking increments, special care shall be taken to obtain representative increments because of the segregation of fine and coarse particles.)
- Sampling from Conveyors
When the increment is taken from a stopped conveyor belt, a section of adequate length in the direction of the stream and of the full width and thickness of the DRI stream, should be taken.
- Sampling from trucks
The increment shall be taken at random from the new surface of DRI exposed during the loading or unloading of the trucks. When it is suspected that there is some bias (between the top and bottom, the front and the rear, or the left and the right) in the DRI in the truck, it is advisable to take increments from each such stratum.
- Sampling from Bunker Discharge
The increment shall be taken at random from the new surface of DRI exposed during the unloading of the bunker.
- Sampling from Stockpiles
The sponge iron should be stacked in geometric shapes preferably 100 mt in quantity. The quantity of sponge iron shall be assessed from bulk density if it is not weighed. The height of the stack should not be more than 1.5 m. A bulk sample from central portion of 1 m to 1.5 m diameter on the top shall be made to expose to the bottom of the stack. The trenches of 0.5 m, Min depth shall be made longitudinally on four sides to expose the materials. Samples with the help of double scoops shall be collected in such a manner that the size distribution of the sample shall be proportionate to the size distribution of the stockpile. The scoop should be moved from bottom to the top of the trench.
Procedure for sample preparation:
The preparation of samples of DRI shall be conducted with extreme care to minimize the chance of reoxidation due to dampness, overheating or both. All equipment should be thoroughly cleaned to remove remnants of deleterious material and it is desirable to flush the equipment just prior to use with a small quantity of the same DRI.
The crushing and grinding shall be conducted with a crusher and a grinder suitable for the size and mechanical strength of the DRI particles. The crusher and grinder should be purged just before use with DRI from the same source. Precautions shall be taken to minimize overheating and reoxidation and to avoid the production of flakes of metal.
From the gross sample (+)10 mm size shall be crushed to (–)10 mm with the help of jaw crusher and mixed along with (–) 10 mm fractions already screened. The mixed material shall be split up for reduction of volume. When the sample quantity attains around 5 kg, then the material is further crushed to (–)6 mm, mixed thoroughly and divided by splitter till the final quantity is around 1 kg. The sample thus obtained shall be ground in disc grinder to (–)150 micron size. Special precautions should be taken to ensure that grinding process does not generate excessive heat which could significantly change the chemical composition.
Mixing By mixing the sample thoroughly it can be made homogeneous and consequently the errors in sample division can be lessened. The mixing maybe conducted either by a mechanical mixer or by hand. The mixer shall be selected to suit the sample and its particle size.
Sieve analysis: The test sample for size analysis should be prepared from each increment, each partial sample or the gross sample without mixing.
Test Sample for Chemical Analysis: The test sample for chemical analysis may be prepared from each increment, each partial sample of the gross sample. A test sample of 100 g, Min at (–)150 micron in particle size shall be prepared.
