[Narrator] The Pellet Fuels Institute is a trade organization that has established
standards in order to grade pellets as premium, standard,
or utility. In this video, Penn State graduate student Jaya Tripathi, demonstrates how to
determine one of the properties used in this grading system: the pellet durability index.
[Tripathi] We first meter the diameter of our pellets,
so that we can select a sieve with slightly smaller mesh openings.
We then sieve our pellets to remove any fines before we start the tumbling test.
We then measure about 500 grams of pellets,
which will be our ensure weight or the start of the tumbling test.
This is our tumbler. It consists of a closed-in, square box mounted on a shaft,
that is rotated by a motor. We place the 500 grams of pellets inside the tumbler.
And then close the door.
We turn on the tumbler and let it run for 10 minutes at a speed of 50 revolutions per minute.
After ten minutes, we turn off the tumbler.
And we start taking out the pellets.
We again sieve those tumbled pellets to remove the fines.
The last step is to measure the final weight of the pellets after removing the fines,
that were generated due to tumbling. Here, in this case, the final weight is 488.4 grams.
Now, we can calculate the durability index of our pellets.
The previous weight, or the weight before the tumbling, was 500 grams,
and the weight after the tumbling is 488.4 grams.
The pellet durability index or PDI is equal to the weight after tumbling,
divided by the previous weight, of the pellet,
times 100. So, it would be for 88.4 / 500 times 100. Which gives the value of 97.6%.
According to the Pellet Fuel Institute, pellets with PDF value of 96.5% or greater, are graded as
premium, which means the pellets that were tested are of premium grade in terms of durability.
So, now you can also determine the durability of your pellets using this procedure.