The validity of the SmartCEMS® PEMS model is entirely dependent on the training data set and the quality assurance program in place at the site. If a comprehensive model is developed initially, there would be no reason to limit the range of time that it would be valid.
An initial model that includes all normal operations, startups, shutdowns, and transitional operating states is deemed ‘robust’ and will provide valid predictions for compliance purposes for many years. The model can easily be retrained, if required, for any extreme, ambient, or other operating conditions not encountered during the initial training data collection.
The system keeps track of when the model is valid for a given set of process data in real-time and provides alarms for tracking excursions from the established model envelope and records the status of the model prediction automatically. Requirements for a periodic or annual recertification test would be dependent on the local regulatory requirements and the facility quality assurance program.
We would recommend retraining the PEMS model (and recertification if required) following any major process change, such as the addition of pollution controls or for changes in fuel and fuel quality. Validation of the PEMS model can be conducted following tuning or annual maintenance activities (such as an extensive overhaul) but this would not be mandatory. The PEMS can be retuned at any time (periodically or continuously) using existing CEMS equipment or by mobilizing temporary or mobile emission monitoring equipment and collecting the process data concurrently with the target pollutant emission rates.