Leaking gas from a snow-covered pipe: empirical evidence and modeling of preferential flow paths

Abstract

The potential dangers associated with exposed fuel gas pipes in areas of significant snowfall are examined. There have been numerous incidents in the past two decades where snow loading or impact on fuel gas equipment has been identified as one step in the sequence of events leading to fires or explosions. This study experimentally and numerically examines the possibility of snow cover creating a preferential pathway for gas flow into a nearby structure from a leaking pipe. Simple experiments show that when a suspended pipe is covered with snow, a gap often forms directly underneath the pipe, which has the potential to serve as a low-resistance flow path for fugitive fuel gas. Using a simplified geometry, the fraction of gas entering a nearby structure from a leaking, snow-covered pipe is examined using finite differences to solve the flow equations in porous media. The snow cover is shown to force a large portion of the fugitive gas toward the structure under certain circumstances and has the potential to create additional hazards that would not be present without the snow layer. Using sensitivity analysis, the major parameters governing fugitive gas flow are determined, which include internal structure pressure, gap size, snow permeability, and distance of the leak from the structure.