New experimental data coupled with a numerical model and an approximate solution are proposed to predict dissociation time of hydrate plugs in oil sub-sea pipelines. The experimental hydrate plugs are dissociated by the method of symmetric depressurisation, both in a specially designed apparatus and a classical batch reactor. The agreement between the estimation of the model and the experimental data and the simplicity of the approximate equation presents an advantage in estimating the time of hydrate plug dissociation in pipelines. (c) 2005 Published by Elsevier Ltd.