Experiments have been performed to study evolution and interaction of bubbles over three inline submerged orifices. Complete, partial and non-coalescence patterns are observed during the growth of bubbles at similar and dissimilar spacing and diameter of orifices. When orifices are equispaced and similar in size, symmetric interfacial shape is observed during coalescence, but unequal orifice spacing resulted in asymmetric merging of bubbles. Drainage of liquid before initiation of coalescence and growth of gaseous bridge between bubbles before unification are observed for both symmetric and asymmetric arrangements. Effect of gas flow rate has been observed for equal and unequal spacing. Delay in merge time is one of the important parameter which has been observed in case of unequal orifice spacing distances and its effect is analyzed for different air flow rate into the liquid tank. Scattered regime plot has been shown in order to understand the bubble coalescence and non-coalescence patterns in different zones and combinations of orifice sizes and orifices spacing. (C) 2017 Elsevier Ltd. All rights reserved.