“Grrrr, I can’t make it daddy! It keeps falling apart!” whines my four-year-old son. We are in the back garden playing with his diggers and dump trucks. He is trying to make a hill (my mind automatically jumps to stockpiles), from dry beach sand, so that he can drive his 4×4 trucks on it. With very free flowing beach sand, this objective is nearly impossible. With my knowledge of bulk materials handling kicking into high gear, I begin to ponder ways to achieve his objective:
- add moisture
- add coarser material
- add a binding agent
- modify the objective
- trade in child for a less demanding version
With the last option ruled out by my wife, I choose to add readily available water. The addition of moisture will make the sand more cohesive and help it to retain its shape… but how much to add? We begin to experiment. One quick squirt of a hose results in no discernible change, two squirts, then three, then four then – slop! Add more sand! Finally, we achieve the objective and the sand retains it shape. I leave him to play.
He’s back less than a minute later, “The sand won’t come out of my digger!” Alas, we have made the sand too cohesive and it won’t come out of the bucket of his front-end loader or the back of his dump truck. Clearly we need a liner for the dump truck that has lower friction. We settle on taping wax paper to the truck bed. Without readily having a robust liner to fix the issue with the digger, we take it out of the equation by using a small hand trowel to fill his dump truck. This seems to work to his satisfaction although it is a very manual solution that will need to be addressed at some later date.
Five minutes later, after beginning to build the stockpile in his desired location (the middle of my lawn), he comes running over and says, “It’s taking too many dumps to build the pile daddy! Can we get a bigger dump truck?” Ah, the desire for increased throughput combined with the clever ploy of getting a new toy! I quickly discard this capital expenditure, and say, “Not going to happen!” Many loads later we manage to make, at least in my son’s mind, the “perfect pile”.
Now I realize, as I reflect on the morning’s escapades, that I should have characterized the material properties of the sand, understood the desired throughput, and clearly identified the objective/goal of the project before embarking on this mission. While my trial and error approach ultimately worked, can you imagine this scenario playing out with a billion dollar bulk materials handling project?