On a recent, long drive from Birmingham to Memphis a discussion broke out regarding the things a rigger needs to know before rigging a load.
The first two things always at the top of the list are: the load’s weight and center of gravity. Incidentally, I sidetracked the conversation when I asked, “But which one is the most important?”
You can imagine the deep, philosophical discussion that question set in motion. Without knowing the load’s weight there cannot be a center of gravity. Likewise, without knowing the center of gravity, there would be no weight. This part of the conversation ate up about 30 minutes of our long trip, but it got the juices to stirring.
I don’t think these two items should be number one or two in any particular order. They should both be number one. This number one question the rigger must determine, load weight and CG, is the foundation to any lifting operation. And they cannot really be determined independent of each other.
If you are using a mobile crane or overhead crane, without knowing the load’s weight, no decision can be made as to whether the crane can make the lift. Further, the position of the crane hook over the load is determined by the center of gravity. Lastly, without the weight and the center of gravity, the length and size of the slings cannot be determined. Remember the slings hold the hook over the center of gravity and prevent the load from rotating around the center of gravity (load control).
I am afraid that if we truly knew how many loads were lifted every day without first arriving at the answer to question one, we would be shocked.
Rigging is not a guessing occupation, it is a thinking occupation.
Don’t be a guesser, be a rigger.
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