INTRODUCTION Maintenance is the cornerstone of asset sustainability. An effective preventive maintenance program, combined with good operational practices, will reduce the need for much corrective and emergency maintenance, as well as total operating cost. A good preventive maintenance program will service not only mechanical and electrical equipment, but also the infrastructure and utility systems required to support the production process. MAINTENANCE HISTORY 1. In the period of pre-World war II, people thought of maintenance as an added cost to the plant which did not increase the value of finished product. 2. During and after World war II at the time when the advances of engineering and scientific technology developed, people developed other types of maintenance, which were much cheaper such as preventive maintenance.