WITS_Mining_Dust Test_Adeline Choh_Draft

Apr 23, 2026 21:40 · 8:06 · English · Whisper Turbo · 2 speakers

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Lecture Index

0:09

S… Speaker 1 (WITS_Mining_Dust Test_Adeline Choh_Draft)

Hello everyone. Welcome to the Mining Engineering Laboratories. My name is Ms. Adeline. I'm here to present to you the Gravimetric Dust Sampling and Assessment Lab.

0:21

S… Speaker 1 (WITS_Mining_Dust Test_Adeline Choh_Draft)

Gravimetric dust sampling for risk assessment is a legal requirement for every mining company. The purpose of this lab is to determine the time weighted average readings over full shifts for different job categories for employees working on the ground and on the surface. Time weight average is the average exposure to hazardous substance, which in this case is called dust over a full shift.

0:49

S… Speaker 1 (WITS_Mining_Dust Test_Adeline Choh_Draft)

Welcome to the DAS lab. Now we are proceeding to the experiments. Here are the equipment that we use for this experiment. We have the wet and dry bulb thermometer, which will be used for measuring room atmospheric conditions. We have the sampling pump set at a flow rate of 1.9 liters per minute. We have two flexible tubes. We have filter papers and supporting pads.

1:18

S… Speaker 1 (WITS_Mining_Dust Test_Adeline Choh_Draft)

The filter papers have to always be exposed to room conditions at least 12 hours before sampling. We have an electronic microbalance which must be allowed to warm up for at least 30 minutes before use. The microbalance is sensitive to vibrations and the stability of the workbench. Check the spirit level to make sure it is in the center.

1:48

S… Speaker 1 (WITS_Mining_Dust Test_Adeline Choh_Draft)

We have a tweezer which is used for picking up the filter paper and the supporting part. We have a cold dust in a glass jar. We have a stopwatch that will be used for timing the run time. Now we're moving to the procedure. Always make sure you have an N95 face mask on. Now I'm using the wet and dry bulb thermometer to measure.

2:17

S… Speaker 1 (WITS_Mining_Dust Test_Adeline Choh_Draft)

atmospheric moisture in the room. I've turned on my micro balance and I'll allow it to warm up for at least 30 minutes. I've checked if my battery is charged and I've equally checked if my filter holders are clean. We have three references labeled 1 to 3 and 10 fields labeled F1 to F10. I'll start by weighing my filter papers.

2:44

S… Speaker 1 (WITS_Mining_Dust Test_Adeline Choh_Draft)

I will start with reference 1, 2 and 3 and I will take 3 consecutive readings which I will record on a sheet. I will repeat this way for all 10 fields. Now I am placing the supporting part on the outlet side of the filter holder and I place the filter paper on top of the support part.

3:16

S… Speaker 1 (WITS_Mining_Dust Test_Adeline Choh_Draft)

I'll close the filter holder using plastic plugs and then I'll remove the plastic plugs. I'll connect the flexible tube to the pump. Now I'm connecting the pump to the outlet end of the filter holder. I'm connecting the second flexible tube to the inlet end of the filter holder.

3:46

S… Speaker 1 (WITS_Mining_Dust Test_Adeline Choh_Draft)

I have to check for air leakages and this is how I do it. I use my thumb to close the mouth of the flexible tube and then I'll start the pump. I'll check the flow rate to see if it remains at zero until when I release the opening of the tube and then it has to jump back to the 1.9 liters per minute level. Now I'm doing the sampling. I'm placing the inlet flexible tube.

4:15

S… Speaker 1 (WITS_Mining_Dust Test_Adeline Choh_Draft)

into the jar containing the cold dust. Approximately five millimeters away from the cold dust. I'm running by palm for four seconds. After four seconds, I'm removing the flexible tubes connected to the filter holder. Starting with the outlet, I'm making sure the filter holder is held upright with the inlet facing upwards. This is to ensure

4:45

S… Speaker 1 (WITS_Mining_Dust Test_Adeline Choh_Draft)

that the collected particles do not fall off the filtered paper as we know that the force of gravity holds true. For the purpose of this video, I'll just demonstrate to you one reference and one field. But if you have to carry on the experiment, all three references have to be done and all ten fields have to be sampled.

5:15

S… Speaker 1 (WITS_Mining_Dust Test_Adeline Choh_Draft)

And the process is the same for all three references and all 10 fields. I'm done with the sampling. Now I'm taking the atmospheric humidity again using my wet and dry bulb thermometer. And I've recorded the reading. Now I'm weighing the reference papers to check for any changes caused by moisture. And I have to do this for all three references.

5:44

S… Speaker 1 (WITS_Mining_Dust Test_Adeline Choh_Draft)

But for the purpose of this demonstration, I will only show one, which is reference one, and I will take three consecutive readings. I will record them on sheet two. I will repeat the wait taken for the ten fields, and I will start with field one. But for the purpose of this video, I will only demonstrate field one.

6:11

S… Speaker 1 (WITS_Mining_Dust Test_Adeline Choh_Draft)

And the same procedure has to be repeated for all 10 fields. I'll wait until the little star on the screen of the micro balance stabilizes and then I take my readings. I'll record them on sheet 2. Now I've completed the sampling and I've recorded the weights in sheets 1 and 2. You have to use these weights.

6:43

S… Speaker 1 (WITS_Mining_Dust Test_Adeline Choh_Draft)

to do the following calculations. Gross mask, which is given by mask after sampling minus mask before sampling. Correction factor, which is given by mask of reference filter after sampling minus mask of reference filter before sampling. The correction factor calculation is to account for the effect of moisture content.

7:17

S… Speaker 1 (WITS_Mining_Dust Test_Adeline Choh_Draft)

This is given by gross mass minus correction factor. The time weighted average, which is given in milligrams per meters cubed, is equal to mass of dust divided by sampling rate times shift time. This brings us to the conclusion of this lab demonstration. Thank you for watching.

7:45

S… Speaker 2 (WITS_Mining_Dust Test_Adeline Choh_Draft)

And you are welcome anytime to Mining Engineering where your future lies.

This transcript was generated by AI (automatic speech recognition). May contain errors — verify against the original audio for critical use. AI policy

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