Monday, April 13, 2009

Excessive Flaming - LOI

One issue commonly encountered when testing materials for ash/loss on ignition (L.O.I) is excessive flaming. Violent, uncontrolled combustion in a crucible doesn’t normally precede high precision test results. As a workaround, it’s common when testing flammable materials for ash by conventional methods such as a muffle furnace that a stepwise approach to heating be applied. First the sample is brought to a temperature where it will smolder, but not flame. The temperature is increased slowly over time until the desired test temperature is reached. While this approach works, it significantly increases test times. It also requires that the operator stop what they’re doing at regular intervals to step up the temperature on the muffle furnace. It’s an effective, if not altogether operator friendly process.

Modern rapid ash/L.O.I. analyzers like the MAX® 5000XL can automate this process and make it essentially painless. Perhaps more importantly, they can offer a granularity of control that is not possible under the classic operator intensive method. The only investment is a bit of up front programming on the part of the operator. Consider this extreme process:

Heat sample from 60°C to 250°C
Hold at 250°C for exactly 8 minutes
Heat from 250°C to 400°C at a controlled rate of 5°C per minute
Hold at 400°C for exactly 15 minutes
Heat from 400°C to 600°C
Hold until rate of weight loss in the sample is less than 0.0500%/minute

A process like that would be impossible for a human operator to execute once, let alone replicate for multiple trials. However once the programming is done, not only can the MAX® 5000XL execute these steps, it can export all the data to an Excel file so that the operator can examine any portion of the process in detail.

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