Reliability assessment and improvement of the electrical : control and instrumentation systems of a cement plant baking process using FMECA

Abstract

The present work is a contribution towards a solution of some important reliability problems as found in some existing Algerian cement plants focusing on the baking system, the heart of the process, with special emphasis on electrical and electronic systems. Any fêlure that leads to shut down of the baking system will inevitably force the process to stop with heavy economical losses; these problems are further compounded by serious maintainability and safety problems which must be faced during the effort of putting the system back into operation. Reliability assessment is developed focusing principally on the electrical and electronic apparatus and devices of the cement baking process. For this, Failure Mode Effects and Criticality Analysis (FMECA) in conjunction with Fault Tree Analysis (FTA), Event Tree Analysis (ETA) and Reliability Bloc Diagram (RBD), are developed in order to determine all possible types of failures and the types of failures that will most negatively affect the operational capability of the system considered. . This is done by gauging the level of failure criticality by working out a Risk Priority Number (RPN). Critical subsystems, circuits and components are identified and classified for its use in a subsequent decision making process in order to take actions in the frame work of a Reliability Centred Maintenance (RCM) with the objective of achieving the required reliability level in a cost effective manner. Are the object of particular attention, the ways and means of reliability enhancement of the Process Control and Instrumentation (PCI) subsystems; the most adequate choice of solutions among several are proposed to improve the reliability of sensor-transmitters, electric drives, controllers and power supply. In the course of this research effort, investigations have been carried out to set up field data base with particular reference to Algerian cement plants with the use of other main sources such as The American Military Handbook Standards series, the MIL- HDBK 217 F, AVCO corporation and Faradip data bases