This paper presents a method for assess the risk index in a power transformers park, risk index is a metric that allows park administrator to ensure an optimal physical asset management, allocating properly financial and human resources in operation and maintenance actions. Assessing risk index requires calculating two secondary sub-index termed failure probability and consequence factor. Those indexes are integrated into the risk index value. In order to illustrate this process, 16 units risk index is evaluated, those units operates in the national Ecuadorian electric grid, results and discussion are finally presented.