A Fuel Ratio Method for Estimating the MESG of Nitrogen-Diluted and Oxygen-Enriched Fuels, Including the Brandes-Redecker Method to Estimate the MESG of Mixed Fuels

Properly specifying electrical equipment for hazardous (classified) areas requires information about certain properties of the materials anticipated to be present. While it is a straight-forward procedure to test a product or stored intermediate in order to establish a Group designation, testing is not in-expensive. Additional difficulty can arise when the electrical equipment design must account for in-process compositional variations.

This paper expands on published MESG data for four nitrogen-diluted and oxygen-enriched fuels, hydrogen, ethylene, propane, and methane. The data is compared to predictions of the NFPA-497 pseudo-MESG technique to account for nitrogen dilution. A new Fuel Ratio method is presented, which provides a closer, more conservative estimation of nitrogen-diluted mixture properties. The Fuel Ratio method is also applicable to oxygen-enriched fuel streams.