Risk and Safety Engineering, Operability Technique, FMECA Approach in the Identification Hazards - Case Study Example

RISK АND SАFЕTY ЕNGINЕЕRING Name Institution Subject Instructor Date Hazard analysis based on checklist The involvement of checklist in performing hazard analysis in very significant in addressing safety implications associated with the operation and maintenance of the steer-by-wire system in vehicles. The reliability of the steer-by-wire system in concerned with making sure that the performance of the system achieves the required mission or task while at the same time upholding safety requirements. Hazard analysis based on checklist for the steer-by-wire system ensures that mishap or accidents that may take place in the course of operation or maintenance do not take place. Their identification is made early for purposes of taking the necessary precautions. There are usual failures encountered that can only cause interruptions that are benign to the system and its users. However, some failures may lead to catastrophic interruptions. Hazards in steer-by-wire system are not desirable and could range from negligible hazards to catastrophic hazards. The kind of hazards resulting system failure are very common in both electronic and mechanical systems. It is thus important to perform the relevant and effective checklist hazard analysis for the operation and use of steer-by-wire system in vehicles. This analysis is concerned with the identification and elimination of hazards whose inherent existence in the system may be bringing about with other failures (Kelly, 2006). General operation environment 1. Are all the components of the system arranged in an orderly manner? 2. Are all the requirements necessary for smooth functionality of the system in place and functional? 3. Are there any foreign objects that could interfere with the smooth functionality of the steer-by wire system? User safety 1. Is the user conversant with the control and operation of the steer-by-wire system? 2. Is the controller or the user of the system under any physical threat in the event of a mishap coming from the system? 3. Is the user or operator equipped with the necessary safety equipment while operating or controlling the system? 4. Is there any health safety threats associated with the use or control of the system? HAZOP technique In the system of steer-by-wire, HAZOP Hazard and Operability technique of analysis offers a systematic and structured way of risk identification, evaluation and management. In particular, the use of HAZOP techniques is often involved in the identification of potential hazards in the steer-by-wire system. This technique is also involved in the identification of the problems and risks that are associated with the functionality and operability of the steer-by-wire system. The hazard and operability technique of analysis is based on a theoretical assumption that risk occurrences are brought about by deviation from operating or design intention of the system. In this approach, the identification of design and operability hazards involves the use of a systematic table that contains the deviation perspectives. The technique is unique in that it assists in the stimulation of the thinking that explores potential deviations by the system (Crawley, Preston and Tyler, 2008). The identification of casual events and hazards in the steer-by-wire system largely uses the HAZOP approach. This is because the technique is most appropriate for the assessment of hazards and casual events in the design of systems, functionality as well as maintenance. The approach is also capable of performing assessment of the system from various perspectives. A fragment of the HAZOP table for the steer-by-wire system could involve items as follows: Item Deviation Probable causes of deviation Results of deviation Necessary precautions Hand wheel Rigidity Poor handling Lack of sensitivity Proper handling Steering column Horizontal shifting Impacts Fracturing Regular maintenance Intermediate shaft Horizontal shifting Impacts Fracturing Regular maintenance Power assist unit Low power production Lack of proper maintenance Low power efficiency Regular maintenance Gear assembly Poor engagement Impacts Gear fracture Regular maintenance HAZOP is best suited for assessing hazards in facilities, equipment, and processes and is capable of assessing systems from multiple perspectives: The items in the HAZOP table 1. Concerned with the assessment of the ability of the design in meeting the specifications and standards of safety for the user 2. Identification of weaknesses associated with the design and operation of the system 3. Assessment of the environment in ensuring that the system is placed and functioning in an appropriate environment 4. Assessment of the controls of the system to ensure that are properly functional and are accurately responding too commands or prompts 5. Operability assessment of the system in term of various operational modes such as the steady and unsteady states, start-up modes, normal operation, and normal shut down, as well as emergency shutdown among others. FMECA approach in identification of system hazards The use of FMECA approach in the identification hazards that are associated with the steer-by-wire system is concerned with the probability and severity assessment off certain specific hazards. In this particular system, the FMECA approach operators as an inductive approach, which involves the identification and evaluation of the mods of failure that are associated with the design of the steer-by-wire system. It also involves the determination of controls or actions that play a major role in the elimination or reduction of the system risks related to potential failure (Grimvall, 2010). This use of this approach is largely applicable in the automotive industry where a very significant role in the enhancement of reliability, operational issues as well as issues related to trouble shooting of the systems. The other role that it plays is that is acts as a standalone tool for the identification and examination of hazards. The use of this approach considers integration of comprehensive hazards. The use of FMECA approach in identifying hazards involves key steps (Crawley, Preston and Tyler, 2008): 1. The identification and listing of components, their function and their mode of failure while considering all modes of operation 2. Determination of the effects associated with each mode of failure on other components of the system as well as, on the entire system. 3. Determination of the severity that I associated with the modes of failure, cause of the failures that have high occurrence probability, and the probability that a potential cause will take place. 4. Identification of the system controls that ensure failure control 5. Determination of the severity and occurrence ranking for the associated risks 6. Re-evaluation of the rankings based on occurrence and severity rankings 7. Documentation of the outcomes of FMECA in a tabulation form as shown below: Item Potential mode of failure Severity of the failure Potential failure effect Potential failure cause Severity rank Hand wheel No out put low Degraded steering Rotor bound 5 Steering column Low efficiency intermediate Loss of steering contamination 3 Intermediate shaft Bound output high No output from motor Short in the windings 2 Power assist unit Low efficiency high Insufficient power supply overheating 4 Gear assembly Improper engagement high The position of motor is locked Gear fracture 1 Partial qualitative fault tree The partial qualitative analysis of fault tree technique involves the specification of undesirable states of the steer-by-wire system. In most cases, the analysis of the state of the system takes place from a critical perspective of safety. The analysis of the system also takes place with regard to its functionality and surrounding in attempts to identify the possibility of occurrence of the undesired events. The faults involved in this steer-by-wire system include the events that are involved in hardware failure of the system. The fault tree indicates logic of interrelations of key events that bring about an event that in undesirable (Grimvall, 2010). The undesired event forms the top event in the fault tree. Accident severity table Item Accident severity level Potential failure effect Potential failure cause Accident severity rank Hand wheel low Degraded steering Rotor bound 5 Steering column intermediate Loss of steering contamination 2 Intermediate shaft high No output from motor Short in the windings 1 Power assist unit high Insufficient power supply overheating 4 Gear assembly high The position of motor is locked Gear fracture 3 Risk classification table Item Associated Risks Risk classes Risk consequence Risk reduction Risk rank Hand wheel Breakage Occasional Marginal Proper reinforcement 5 Steering column Fracture Probable Catastrophic Proper reinforcement 2 Intermediate shaft Fracture Incredible Catastrophic Proper reinforcement 1 Power assist unit Efficiency reduction Frequent Critical Regular servicing 4 Gear assembly Disengagement Remote Critical Regular servicing 3 Justification The process of risk identification and reduction in the steer-by-wire system is appropriately justifies its use in automobiles. Almost all personal mobility and industrial utilities have sorted for the introduction of the steer-by-wire system in the automotive. If not, then there are initiative in progress towards its introduction in the near future. This is because of its simplicity in operation, maintenance and low risks involved. The adoption and use of the system also results in a considerable reduction of maintenance cost and other associated costs. Qualitative and Quantitative IEC 61508 approach In order to realize the establishment of the required and expected Safety integrity Level (SIL) value associated with the Equipment under Control, the adoption of IEC 61508 approach is an important initiative. This is mainly to enhance the safety of the equipment under control. The IEC 61508 approach in the international standards is largely acceptable as a basis for design, specification and operation of the system of safety. With regard to a qualitative approach, this approach is appropriate and useful. In this case, it involves extensive analysis of the steer-by-wire system while taking into account all the possible risks involved. The adoption of a quantitative approach with regard to the fault tree analysis of this system involves a series of development safety considerations. Further, it involves the application of a Quantitative Risk Analysis, which simplifies the application of IEC 61508 for the safety requirement standards for the Equipment under Control. (Safety-critical systems symposium, Dale and Anderson, 2012) References Crawley, F., Preston, M., & Tyler, B. (2008). HAZOP : guide to best practice: guidelines to best practice for the process and chemical industries. Rugby, Institution of Chemical Engineers. Grimvall, G. (2010). Risks in technological systems. London, Springer. Kelly, A. (2006). Strategic maintenance planning. Oxford, Elsevier/Butterworth-Heinemann. Safety-critical systems symposium, Dale, C., & Anderson, T. (2012). Achieving systems safety proceedings of the twentieth Safety-Critical Systems Symposium, Bristol, UK, 7-9th February 2012. London, Springer. Read More