The scope of this International Standard covers turbines, storage pumps and pump-turbines of all sizes and of the following types: Francis; Kaplan; propeller; Pelton (turbines only); Bulb. Wherever turbines or turbine components are referred to in the text of this guide, they shall be interpreted also to mean the comparable units or components of storage pumps or pump-turbines as the case requires. The Guide also identifies without detailed discussion, other powerhouse equipment that could affect or be affected by a turbine, storage pump, or pump-turbine rehabilitation. The object of this guide is to assist in identifying, evaluating and executing rehabilitation and performance improvement projects for hydraulic turbines, storage pumps and pump-turbines. This guide can be used by owners, consultants, and suppliers to define: needs and economics for rehabilitation and performance improvement; scope of work; specifications; evaluation of results. The Guide is intended to be: an aid in the decision process; an extensive source of information on rehabilitation; an identification of the key milestones in the rehabilitation process; an identification of the points that should be addressed in the decision processes. The Guide is not intended to be a detailed engineering manual nor a maintenance guide.