Abstract
It is essential to maintain cleanliness in an oxygen system as many accidents occurring in oxygen-enriched environment indicate contamination as a major source of ignition. Computational fluid dynamics (CFD) analyses show that valve seats, T-joints, elbows and spots with complex geometries are possible locations for accumulation of the dust particles. It is important to understand the mechanisms of contaminant accumulation, the initiation of fire and its propagation in valves and regulators in order to suggest ways for their prevention. As contaminant dust particles flow with oxygen through valves and piping systems, the solid dust particles impact or rub with the pipe wall or with each other. This results in the building up of static electric charges in them. These charged dust particles may eventually accumulate and lead to electrostatic discharge, thus creating a potential cause of initiation of fire. The aim of the present work is to develop a mathematical model based on CFD, of the dispersion and settling of micron-sized charged dust particles in the pressure regulator, commonly used in oxygen application. A two-dimensional numerical model of flow, dust particle dispersion and particle settling, utilizing finite volume approach, has been developed on FLUENT 6.3.26 platform. The results show that there is a possibility of electrical discharge due to the settlement of charged dust particles if a regulator is attempted to be reopened within a short time of it being closed. Since it is practically impossible to make all oxygen systems free of contaminants at all times, it may be worthwhile to analyze ways about how to avoid ignition even in presence of large concentration of dust particles. The present study may give an insight into the possibility of ignition and offer suggestions to avoid it through appropriate system configuration and operation timings.
