Back to the Basics: Rate-of-rise alarm

An alarm which activates when the rate of increase in solvent concentration exceeds the rate alarm level, can give early warning when a severe upset condition exists that is likely to eventually result in a very high solvent concentration. 

Because the alarm triggers on a change in reading per second, and not a reading level, the rate alarm can activate at the very beginning of the analyzer's response time rather than several seconds or more later when the reading has finally climbed above the warning or danger alarm levels. 

Back to the Basics: Routine Testing of Alarms

A positive test for correct operation of critical alarms is essential. 

At a minimum this should be performed as part of a regular yearly audit that includes verification of the alarm relays, alarm annunciators, fault relays and all corrective actions, including:

  • shut-down 
  • emergency-stop 
  • dampers 
  • off-coat 
  • burners 
  • horns 
  • lights

Back to the Basics: Two Alarm Levels

Two alarm levels provide a more complete system less likely to cause unwanted shut-downs. 

Back to the Basics: Operator Training & Visibility of Alarms

Regardless of the amount of automation in the process, it is critical to train all personnel, including operators and maintenance workers, on the exact meaning of the analyzer readings and alarms.

Following any shut-down, the process should not re-start until the alarms have been manually reset and cleared, and the cause of the alarm understood and corrected.

The alarm and reading of the analyzer should also be easily and quickly visible by the operator, so that prompt and clear actions can be taken in response to a dangerous condition.