Reliability, Availability, and Maintanability (RAM) Study Slides
- 1. RAM Study
- 3. Reliability • The probability that an item will perform a required function, under stated conditions, for a stated period of time. • Systems should be as failure-free as possible. • Reliability of a system can be improved in several ways, including: 1. Select reliable equipment with quality components that are rated for the appropriate environment. 2. Design to eliminate failure modes. 3. Design with appropriate redundancy. 4. Ensure the system integrity can be maintained throughout the life of the system, including design for physical protection of the system itself
- 4. Availability • The proportion of time for which the equipment is able to perform its function. • The probability that a system is not failed or undergoing a repair action when it needs to be used. • Availability is how long the system performs required functions and may be expressed as:
- 5. Maintainability • The ability of a component to be retained in, or restored to, a specified condition when maintenance is performed using prescribed procedures and resources. • It is a characteristic of design and is essentially a measure of the ease with which the system can be maintained. • Maintainability is often expressed as mean time to repair (MTTR), or how quickly the system/equipment can be restored to its function.
- 6. RAM Study • A strategic approach for integrating reliability, availability and maintainability, by using methods, tools and engineering techniques (e.g. Mean Time to Failure, Equipment Down Time and System Availability Values) to identify and quantify equipment and system failures that prevent the achievement of the productive objectives. • In simpler words, to predict problems before they occur. • RAM Study has been applied in various area such as: 1. Oil & gas industry 2. Electrical systems 3. Physical security systems 4. Military systems 5. Space stations
- 7. General Objectives of RAM Study 1. To accurately forecast availability and/or capacity given the equipment selected and maintenance plans deployed 2. To identify any significant causes of loss of operational availability or issues that may limit the production throughput 3. To document reliability strategy data for handover and to support continuous improvement 4. To generate quality maintenance plans and master data cost effectively 5. To optimize system/process/equipment design to meet requirements at minimized costs
- 9. What is needed to perform a RAM study? RAM Design Basis Reliability Data
- 10. Design Basis • System Life: For design studies, this would be defined as the design life For studies during operations, it might refer to a specific period of time e.g. 15 years. • Design capacity of the different units • Equipment list: this data will vary depending on the study level. For the design phase, production-critical items are typically used For manning studies, non-production critical items would also be included to assess the delays related to maintenance logistics
- 11. Design Basis • Process Flow Diagrams (PFDs): A PFD is a diagram commonly used in engineering to indicate the general flow of plant processes and equipment. • Process and Instrument Drawings (P&IDs): A P&ID includes more details than a PFD. It includes major and minor flows, control loops and instrumentation. • These diagrams will be used to transform design information into a Block Flow Diagram (BFD) and Reliability Block Diagram (RBD). BFD RBD • The connectivity of nodes and focuses on the production aspects of the system e.g. flow rates and product mass balances • Each node within the network will require its own RBDs • These are used to identify the system’s components and their operating mode. • Once we know what equipment items to be included in the model, we start looking into collecting reliability data.
- 12. Reliability Data • Among potential sources of reliability data include: 1.Generic data sources (i.e. OREDA, IEEE, etc.) 2. Vendor data. 3. Data derived from the Computerized Maintenance Management System (CMMS). 4. Engineering judgement and available techniques (such as FTA) to identify failure modes for new technology where data is not available.
- 13. Reliability Data • The reliability data collected should be organized into failure modes; Critical failure (CRT): A failure which causes immediate and complete loss of a system's capability of providing its output Degraded failure (DEG): A failure which is not critical, but which prevents the system from providing its output within specifications. Such a failure would usually, but not necessarily, be gradual or partial, and may develop into critical failure in time Incipient failure (INC): A failure which does not immediately causes loss of a system's capability of providing its output, but which, if not attended to, could result in a critical or degraded failure in the near future Unknown failure (UNK): Failure severity was not recorded or could not be detected • These failure modes could refer to an equipment-level (i.e. pump, compressor, etc) or component-level (i.e. transmitter, valves, etc) analysis.
- 14. Reliability Data • For each of the included equipment items/failure modes, the following data are to be collated; Total number of failures Calendar and operational time during which failures were recorded Average repair times • Using this data, the Mean Time to Failure (MTTF) and Mean Time to Repair (MTTR) for each equipment item/failure mode can be determined. These are the two parameters that contribute to an equipment item's ability or inability to fulfil its role.MTTF (per hours) • The average time between consecutive failures - calculated by dividing the cumulative observed time by the total number of failures • This term only applies to components with exponential failure distributions MTTR (hours) • It is a measure of average time taken to diagnose and restore failed equipment to an operational state • It does not include logistic delays
- 15. Performing RAM Analysis • Followings are the software tools used to perform RAM analysis: 1. ExtendSim 2. BlockSim 3. MIRIAM 4. MAROS - A product of DNVGL - Applied specifically for O&G industry