Each drying process has a unique rate of solvent increase in the normal and upset conditions. The potential maximum rate of solvent concentration increase should be estimated, so that the analyzer has time to generate an alarm, and the method of corrective action has time to reduce the solvent concentration, before a flammable or explosive limit is reached in the dryer.
Some of the factors include:
- dryer volume
- ventilation rates
- line speed
- drying rates
- maximum coating weight
It should be recognized that it is not uncommon for rates of solvent increase to reach 10% L.F.L. per second or more, leading to a flammable or explosive concentration in just a few seconds. It is also possible that the maximum rate of accidental solvent increase is so high that it is not entirely possible, even with a perfect analyzer, to prevent a dangerous condition in the dryer.
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