Accurate prediction of bubble diameter is crucial for the proper design, optimization, and scale-up of gas-liquid apparatuses. Bubble formation at submerged multiple orifices in a gas-liquid apparatus under industrial conditions is systematically investigated in this work. It is found that the bubble diameter firstly increases and then approaches to a relatively constant value in the low viscous liquid when increasing the orifice superficial gas velocity. Parametric studies demonstrate that large orifice diameter and high liquid viscosity lead to larger bubble diameter, and the inflection point in the curve of bubble diameter versus orifice superficial gas velocity is also affected. With surfactant added in solutions, the bubble diameter decreases markedly. Based on the experimental data, a semi-empirical correlation for predicting the bubble diameter is proposed using nonlinear least square optimization. The new correlation, containing the influence of orifice diameter, orifice superficial gas velocity and liquid properties on the bubble diameter, is further validated by comparing prediction results with experimental data over a wide range of operating conditions and working systems from the literature. Therefore, it is thought useful for the industrial design of gas-liquid apparatus. (C) 2019 Elsevier Ltd. All rights reserved.