A series of experiments are carried out to reveal the effect of an obstacle on the explosion intensity of a methane-air mixture in a spherical vessel connected to a pipeline. Results show that obstacle presence, blockage ratio, and position play significant roles in explosion intensity. The oscillation amplitude of pressure both in the vessel and at the pipeline terminus weakens when an obstacle exists in the pipeline. The effects of the blockage ratio on explosion intensity are different when obstacle position changes. Explosive intensity decreases with blockage ratio when the obstacle is set at the intersection of the spherical vessel and the pipeline and in the middle section of the pipeline. Moreover, when the blockage ratio is similar to 56%, the minimum explosion intensity is obtained when the obstacle is set at the middle section of the pipeline. Explosion intensity increases with blockage ratio when the obstacle is positioned near the pipeline terminus. The most dangerous case is when the obstacle is positioned near the pipeline terminus, especially when the blockage ratio is 75% or greater. The maximum pressure and the rate of pressure increase at the point of intersection of the spherical vessel and the pipeline are higher than at the middle section. The conclusions provide an important reference for designing explosion venting safety systems and explosion-resistant designs. (C) 2016 American Institute of Chemical Engineers Process Saf Prog 36: 67-73, 2017