Twenty first century is witnessing highly complex and sophisticated developments on Industrial front where spearheading competitiveness is an emerging phenomenon. In order to offer a competitive price-range for the newly emerging products industries are forced to adopt strategies of cost-cutting and at the same time they need to ensure their own growth in neck to neck demanding situations and also to counter the burn out of the recession. Somewhere they are in pressure of maintaining quality of the product and services for ensuring their own sustainability. In such a messy situation corporate and industries are undergoing through the huge amount of pressure and in that tough and critical hour they are unable to bear the burden of human error any more. These situations lead industries to depend heavily on automation of maximum processes.The book is an attempt to analyze the reliability and profit of a hot standby PLC system. The purpose is to ensure an efficient system to produce good quality product. To make the study useful and practical, real data on failures, repairs and costs of PLC System have been collected.Cost-benefit analysis is done on the basis of collected data.