Considerations When Applying Microprocessor Relays In Chemically Harsh Environments

The evolution of microprocessor based protection, monitoring, and control devices in industrial applications has resulted from a need for smaller, more cost effective protection devices that can provide substantially more metering, monitoring, and reporting functionality than electro-mechanical or solid-state relays. These requirements have led to the use of surface mount components, replacing the larger, more expensive through-hole components. While helping to meet the requirements of the industrial market, the use of surface mount (SMT) technology has produced technical challenges directly related to the industrial environment for which they were designed. Harsh chemical environments, specifically environments that contain gaseous sulphide, can result in the corrosion and ultimate failure of the surface mount components used to manufacture microprocessor-based devices. Although the terminology "Harsh Chemical Environment" is commonly used to describe applications known to contain chemical contamination, it has been established that the levels of hydrogen sulphide (H2S) required to cause failures in surface mount components is scientifically lower than previously thought. This paper will serve to highlight the technical challenges associated with implementing microprocessor-based devices in industrial environments where there is the potential for hydrogen sulphide or other corrosive gas contamination. Among the issues to be discussed; (a) how hydrogen sulphide effects microprocessor based devices; (b) sources and levels of hydrogen sulphide causing component failure; and (c) prevention and containment solutions for industrial applications.