When sampling cement from a lot (consisting of several cement bags), the lot is divided into several sub-lots.
The number of sub-lots into which multiple lots are to be divided depends on the weight of the lot. Use the following table when dividing lots into sub-lots.
Lot Weight |
Number of Sub-lots |
up to 100 |
2 |
101 – 200 |
3 |
201 – 300 |
4 |
301 – 500 |
5 |
501 – 1000 |
6 |
1001 – 2000 |
7 |
Take a sample from at least 2% of the bags, subject to at least five. Pick at least 5 numbers at random. of bags from the sub-lot. Use the following procedure to randomly select bags.
Table of Contents
Process of random sampling for selecting bags from sub-lots
- First count the number of bags in a sub-lot. Let it be “n”.
- Then decide how many bags you need to sample. At least 5 bags should be selected as a guide.
- Divide the total number of bags (ie N) by the number of bags to be sampled (ie N/5). Let it be “X”.
- Now starting with any bag at random, count the bags in the sub-lot in a sequence 1, 2, 3 up to x and so on. every x^{th} The bag thus numbered will be discarded.
taking samples from bags
- Insert the sampling tube (as shown in the picture above) diagonally into the valve of the bag and place your thumb over the air hole and then withdraw the sampling tube.
- Take approximately the same number of increments from each bag as chosen above.
- The weight of each increment should not be less than 2 kg.
sample packing
- Store the sample selected above in a moisture-proof, air-tight container to avoid absorption of moisture and aeration of the sample.
- If the sample is to be stored in a can, immediately fill the can completely and seal it.
- The containers should have suitable identification marks so that they can be linked to the particular sub-lot from which the gross sample is drawn.
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