00:00Do you know why one handful of sand could save an entire train?
00:03Don't laugh. Look closely.
00:05The worker opens the firebox door,
00:07scoops up dry sand and throws it into the red-hot furnace.
00:10Isn't a train supposed to burn coal?
00:12Wouldn't sand put the fire out?
00:14Actually, this sand is not fuel,
00:17and it is not used to kill the fire.
00:19It is the lung cleaner of a steam locomotive.
00:22After an old steam train runs for a long time,
00:24its boiler tubes get covered with soot, oil, and carbon.
00:27That black layer works like insulation.
00:30It blocks heat, so even when the fire burns hard,
00:33the boiler struggles to make steam.
00:35Once sand enters the firebox, hot airflow pulls it into the tubes.
00:39The grains act like sandpaper, scraping carbon off the pipe walls.
00:43Then the dirt leaves with the black smoke.
00:45But sand is even more important on the rails.
00:48A train needs it to start moving.
00:50Rainwater, oil, and even crushed leaves
00:52can create a slippery black film on the rails.
00:54Then the steel wheels can suddenly lose grip.
00:57So dry sand from the sandboxes is sprayed in front of the wheels,
01:00helping them bite the rail again.
01:02That is why one handful of sand can clean the boiler,
01:05stop the wheels from slipping,
01:07and save the train.
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