What is the minimum feedwater sulfite level required when using an economizer?

When using an economizer in a water system, it is crucial to maintain adequate sulfite levels in the feedwater to prevent corrosion in the heat exchange surfaces. Sulfite acts as an oxygen scavenger, protecting metal surfaces from the corrosive effects of oxygen and other oxidizing agents present in the water.

The minimum sulfite level required for effective protection in systems with economizers is 5 ppm. This level has been determined through operational experience and research, ensuring that sufficient sulfite is present to handle the oxygen levels typically found in feedwater. Maintaining this concentration helps to minimize corrosion risks, which can lead to costly equipment failures and operational inefficiencies.

Levels below this threshold may not provide adequate protection, leaving metal surfaces vulnerable to corrosion under the specific conditions present in economizers, which operate with higher temperatures and concentrated contaminants. Therefore, maintaining a minimum of 5 ppm sulfite is essential for ensuring the longevity and safety of the system.