Studies on operating characteristics of control valves with two-phase flow have not been given much attention in the literature despite its industrial importance during design and selection as well as during plant operation. However, literature shows considerable work with two-phase flow through pipes and different geometrical shapes of flow ducts. The present work attempts to study experimentally the effect of two-phase flow on pressure drop across the control valve for different volume fractions of the fluids. A typical fluid system of palm oil (liquid phase) and air (gas phase) has been used for the studies. The pressure drop in a horizontal straight pipe upstream of the valve is also considered to test the correlations from the literature on two-phase pressure drop. The same is extended to represent the pressure drop across the valve. The operating characteristics are obtained from the pressure drop relationship and valve opening. It is found that Lockhart-Martini (L-M) parameter and the quality (fraction of liquid) are found to correlate well with the two-phase multiplier defined based on pressure drop with gas phase. The installed characteristics of the valve for varying pressure drop and quality is presented. (c) 2005 Elsevier Ltd. All rights reserved.