Implementing CEMS Alarms: Nuisance or Necessary?
Alarms on a CEM system can be extremely helpful in managing CEMS compliance as they can help avoid emissions violations or catastrophic downtime situations. However, if alarms are not set up intelligently, they can become nuisances that are often ignored resulting in real problems going undetected. The following are some simple, yet informative alarms that we recommend:
Non-valid data alarms
We recommend setting up alarms for whenever data is invalid for reasons other than normal maintenance, calibrations, or process down conditions. We suggest that these alarms be split up by parameter (NOx, Opacity, etc.). In order to avoid having an alarm become a nuisance, we further suggest to implement a delay instead of having it sent out for every invalid minute. One method would be to create a rule to send the alarm for the first invalid minute, and then once every 15 minutes thereafter. Another possibility would be to only send an alarm only when 15 minutes or more of data is invalid.
Ideally, these alarms would help control emissions before an excess emission is reached. Depending on limits and operating flexibility, the thresholds on these alarms vary. However, the alarm should be configured to provide the operators enough time to make minor adjustments to correct the emissions without disrupting the process unnecessarily. Sometimes it takes trial and error to find a good set point. For instance, 1-minute alarms are typically not very useful (unless for opacity), but a 1-hour alarm may be beneficial for controlling a 4-hour average.
Calibration drift alarms
Sometimes it is not always clear just by glancing at a calibration report if there has been a failure or significant drift or perhaps daily calibration checks are not reviewed on a daily basis. In those cases, implementing an alarm for a calibration failure or major drift can be helpful as a secondary check to ensure excessive downtime is avoided due to a daily calibration failure.
Specific Malfunction Alarms
Often analyzers have numerous internal operational alarms that can be beneficial for troubleshooting and avoiding catastrophic failures. If these are brought into the data system, operators can see them and alert maintenance personnel so they can be addressed in a timely fashion. These could be such things as internal temperature, pressure, or gas flow alarms, which could indicate an obstruction or part failure. There can also be alarms on other CEM system components, such as rack, shelter, and heated sample line temperatures. Any of these alarms can provide valuable advanced warning that something is wrong on the system before excessive downtime is incurred.
Are you questioning whether your CEMS alarms are configured properly? Air Tox can assist with reviewing your current alarm configuration and advise on best practices. Contact us here.