Last week we discussed the first type of process upset that could present a hazardous condition, the steady-state, this week let's focus on on the condition that poses the greatest difficulties in detection and correction.
Process upsets from transient conditions produce a hazard from an unstable process that is changing relatively quickly. Causes include:
There are several fundamental safety precautions which should be applied to all dryer designs.
Once the minimum ventilation requirement is known, dampers must be secured so that ventilation is never reduced below the minimum. The best method is to cut away the damper so that it is not possible under any condition to reduce the ventilation rate to an unsafe level. Manually adjusted stops, and sometimes even welded stops, have been found to be insufficient to prevent accidental loss of ventilation due to incorrect damper settings.
