Our risk and reliability analysis services include: Reliability, availability and maintainability (RAM) analysis; corporate reliability engineering management; Reliability Block Diagram (RBD) modeling; fault tree analysis; failure investigation and analysis; design for reliability (DFR); Probabilistic Risk Assessment (PRA); Failure Mode, Effect, and Criticality (FMECA) Analysis; and Common cause failure (CCF) analysis.
Reliability, Availability and Maintainability (RAM) Analysis
RAM refers to three related characteristics of a system and its operational support: reliability, availability, and maintainability. IEEE Std. 493-2007 (Gold Book) defines reliability, availability and maintainability as:
Reliability: The ability of a component or system to perform required functions under stated conditions for a stated period of time.
Availability: The ability of an item – under combined aspects of its reliability, maintainability, and maintenance support – to perform its required function at a stated instant of time or over a stated period of time.
Maintainability: Ease of maintenance, corrective or preventive, is a function of how well the system has been designed to be maintainable. This aspect of design is called maintainability. Providing ease of access, placing items requiring preventive maintenance where they can be easily removed, providing means of inspection, designing to reduce the possibility of maintenance-induced failures, and other design criteria determine the maintainability of a system.
KimiaPower utilizes various tools and techniques to perform RAM analysis and our report will highlight your readiness for achieving the specified levels of RAM.
Reliability Block Diagram (RBD) modeling
Reliability block diagram is a success-oriented network describing the function of the system. A reliability block diagram is a graphical depiction of the system’s components and its interconnections which can be used to determine the overall system reliability. Reliability block diagram modeling is a method of representing the functional relationships among the components and subsystems and indicates which ones must operate successfully for the system to accomplish its intended function. The blocks in RBD represent the system components and the lines show the interconnections among the components and subsystems. Reliability block diagrams are commonly used in reliability and availability analyses and for safety assessment.
KimiaPower team utilizes RBD modeling for reliability and availability analysis of existing systems or facilities; and also for predicting the reliability and availability of a system during its design stages.
Failure Mode Effect and Criticality (FMECA) Analysis
FMECA is one of the methodologies to identify and analyze potential failure modes of all parts within a system, the effects these failures may have on the system, and how to avoid the failures, and/or mitigate their effects on the system. FMECA is a technique used to identify, prioritize, and eliminate potential failures within a system. Initially, the FMECA was called FMEA (Failure modes and effects analysis). The C in FMECA indicates that the criticality (or severity) of the various failure effects are considered and ranked. FMECA was one of the first systematic techniques for failure analysis. FMECA was developed by the U.S. Military and the first guideline was Military Procedure MIL-P-1629 “Procedures for performing a failure mode, effects and criticality analysis” published in 1949. FMECA is the most widely used reliability analysis technique in the initial stages of product/system development.
KimiaPower team will assist you in performing FMECA and deciding whether a product or service is acceptable or not. In addition, our FMECA reports will include potential improvements to the system to reduce risk by increasing the possibility that the failure is detected in time, reducing the adverse effect of failure, and reducing the likelihood of occurrence of failure.
Common Cause Failure Analysis
Common cause events are those specific groups of dependent events that might adversely affect the operation of a redundant system. Common cause failures (CCF) are considered a subset of dependent failures with a major difference that they cannot be explicitly modeled. A CCF is a single point of failure (SPOF) causing a unit and its “perceived” redundant unit to fail simultaneously.
United States Nuclear Regulatory Commission (US NRC) Guidelines on Modeling Common Cause Failures in Probabilistic Risk Assessments, NUREG-CR5485 has defined common cause failure as an event consists of component failures that meet four criteria:
- Two or more individual components have failed or considered degraded, including failures during demand, in-service testing, or deficiencies that would have resulted in a failure if a demand signal had been received
- Components fail within a selected period of time such that success of the PRA mission would be uncertain
- Component failures result from a single shared cause and coupling mechanism
- A component failure occurs within the established component boundary
Main attributes of CCF can be related to two factors: root cause, and coupling factors. Root cause in CCF is defined as the fundamental reason of item failure that if corrected, would potentially eliminate the re-occurrence of similar failure. Typical root cause failures include various errors in engineering, design, manufacturing, installation, testing, commissioning, operation, execution, and maintenance, as well as environmental stresses such as heat, humidity, flood, earthquake and fire.
Coupling factors in CCF are referred to links and relationships among several items that would make them susceptible to the same root cause. Typical coupling factors include same physical location, same environment, same design, same hardware or software, same installation crew, same maintenance team, and same procedure.
As part of CCF analysis, KimiaPower team will assess systems’ susceptibilities to CCF to consider and incorporate their impact on systems’ reliability and availability and develop design strategies to mitigate these types of hazards.