ABSTRACT Heat exchanger network (H.E.N) is a key aspect of chemical process design and about 30% energy saving coupled with capital saving can be realized by improving the H.E.N design. The objectives of this work are: i) to study the flexibility of H.E.Ns under the simultaneous variations of temperature, heat capacity flow rates and the product of the overall heat transfer coefficient and the area of the heat exchanger. ii) to highlight the dangers and the opportunities for developing a practically applicable technique. Also, a modified method for the flexibility study of H.E.Ns was developed from the combination of two systematic computational methods (sensitivity analysis and heat load shift method). In this method the passive response of the network to the deviations in feed temperature, flow rate, heat transfer coefficient was evaluated by using the sensitivity analysis method while the possible design changes, which are required to eliminate the unwanted passive responses, were determined by using the heat load shift method.