Someone the other day was asking why my crush test results were different from those sent to another lab. It was the same sand!
Here’s the answer:
It’s just not possible that all laboratories and equipment, and technicians are all equal and all accurate and precise and exact, all the time.
Let’s take just the crush test for instance…
There are possible errors introduced, depending on different labs and technicians:
(1) initial washing – washing and scrubbing can be somewhat subjective, as one lab technician might wash sand more thoroughly than another
(2) building crush prep material. Sieves all have tolerances, and they all vary somewhat. And sieves get dirty over time as sand particles are trapped in the mesh. But, they still might test in spec. So, one lab might create a crush prep material that is slightly coarser than another, resulting in perhaps slightly different crush test results
(3) Loading the crush cylinder is a technique that takes a LOT of time to master. Some technicians might load the crush cylinder with a slight slope, which can focus the stress during the crush test
(4) Crush testing itself involves ramping up pressure over a set amount of time, then holding the stress constant for 2 minutes, then quickly releasing
(5) the final step is to once again use sieves to see how much falls through the smallest mesh, and ends up in the pan. Here, if different sieves are used than step 2, it might introduce errors. And this process is repeated, at least 2 or 3 times and the results averaged.
So, through no fault of either lab, there might be different crush test results for similar sand.
In order to reduce any sources of error, at Global Energy Labs we use calibrated equipment, we follow the correct procedures, and we have highly trained and experienced personnel doing the testing.
Beyond that, there are mathematical precisions and compiled errors that no lab can completely eliminate.
To hire a lab that consciously reduces the sources of errors, go here!
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