Study on Gas Diffusion in Fire Working Areas of Oil and Gas Pipelines Based on Temperature Difference

[Image: see text] When a pipeline is under fire safety work construction, the stack effect of the pipeline will increase the diffusion rate of nitrogen, reduce the oxygen content, and cause asphyxia. To prove the influence of the stack effect of the pipeline on the nitrogen movement in the pipeline and put forward effective ventilation control measures, the formation mechanism, gas diffusion law, and ventilation parameters of the stack effect of the oil and gas pipelines are studied through theoretical derivation and numerical simulation. The results show that the nitrogen concentration at the height of the breathing zone in the hot zone first increases and then decreases along the axial distance. The larger the temperature difference, the faster the diffusion speed of nitrogen in the fire safety work area, and the lower the oxygen concentration. When the temperature difference increases to 30 °C, the maximum oxygen concentration in the work area is 0.177; to control the problem of low oxygen content caused by the stack effect, three ventilation schemes are put forward. Through the analysis that installing fans symmetrically on both sides, 4 m away from the pipe opening, can effectively reduce the stack effect intensity when the optimal working wind speed of the fan is 4 m/s. The findings of this study can help in better understanding the causes of the chimney effect during pipeline fire safety work and provide theoretical basis for controlling personnel suffocation caused by the chimney effect.