Concepts Tasks Settings Glossary of SIF Terms The following terms are used throughout the SIF topics. For a full glossary of APM terms, see Glossary. Term Definition Action Plan An action plan in a strategy development analysis identifies an asset’s failure mode and recommends an action to prevent the failure or mitigate its consequences. For example, MTA2 and SIF action types are condition-based maintenance, failure-finding maintenance, scheduled restoration or discard, modification or redesign, and no scheduled maintenance (run to failure). RBI analyses support actions such as inspections, strategy, and modification or redesign. Change Set A change set value in APM is usually a reference to a change request generated by a Management of Change (MOC) system. It provides a basic reference between the request and the change made in APM. You can assign change sets to safety provision versions and strategy development analyses. Condition-based Maintenance A task that entails checking for potential failures so that action can be taken to prevent the functional failure or to avoid consequences of the functional failure. Environmental Consequences A failure mode has environmental consequences if it could breach any corporate, municipal, regional, national, or international environmental standard or regulation which applies to the physical asset or system under consideration. Failure Consequence The way in which the effects of a failure mode matter (evidence of failure, impact on safety, the environment, operational capability, direct and indirect repair costs). Failure Effect What happens when a failure mode occurs. Failure-finding Interval A failure-finding interval is the length of time that it is considered safe to wait before performing failure-finding maintenance. The interval is calculated or estimated based on the desired availability and the frequency of failure of the protective device or system. Failure-finding Maintenance A scheduled task used to determine whether a specific failure has occurred. Failure Mode A failure mode is a single event that causes a functional failure. For example, if a pump’s impeller becomes worn, the pump cannot convey liquid at the required rate. Failure modes are analyzed in maintenance task analysis (MTA2), reliability-centered maintenance (RCM2), and failure modes, effects, and criticality (FMECA) analysis along with the action plans that prevent or mitigate failures. Safety instrumented function (SIF) analyses examine the risk of failure in safety devices, the effects and consequences of failure, and ways to reduce risk by putting safety provisions in place. For risk-based inspection (RBI) analyses, the failure of concern is loss of containment of pressurized equipment items. Examples of failure modes are small hole, crack, and rupture. Failure Mode Consequence Priority A failure’s or failure mode’s consequence priority provides an indication of the relative importance of the asset failure. The larger the number, the greater the severity of the failure. The priority can be used to recommend root cause analysis for a failure or to determine the order of action plan implementations. Consequence priorities are assigned to failure modes during risk assessment. In failure evaluation, the consequence priority is used in the calculation that determines whether the failure is suitable for root cause analysis. APM assigns the consequence priority by comparing the information to a set of customer-defined rules. The consequence priority rules can be based on the failure severity, relative risk (risk analysis only), failure costs, downtime costs, downtime, or a combination. For example, the Extreme consequence priority could be assigned to failures or failure modes whose total severity is greater than 25 or failure costs are more than $25,000. Function What the owner or user of a physical asset or system wants it to do. Function Group A function group is a way of identifying assets that are responsible for performing a particular function. For example, the “Pump Assembly” function group could be used to indicate the relationship between a centrifugal pump, 20 HP motor, and valves. HAZOP Analysis A hazard and operability (HAZOP) study is a structured and systematic examination of a planned or existing process or operation in order to identify and evaluate problems that might represent risks to personnel or equipment or that might prevent efficient operation. HAZOP and SIF strategy development analysis in APM use the same system features. The difference between the two is one of timing and process. HAZOP analysis occurs earlier in the design process and is performed at a higher level. HAZOP analysis is likely to identify the need for a safety provision; SIF analysis ensures that it is in place. HAZOP Checklist A HAZOP checklist item represents an abnormal operating condition, such as high flow, low level, or incorrect valve positioning. Checklist items are listed in SIF and HAZOP analyses, where failure modes can be created to assess causes, effects, consequence severity, risk levels, and more. No Scheduled Maintenance A failure management policy that permits a specific failure mode to occur without any attempt to anticipate or prevent it. Also referred to as “Run-to-Failure”. Non-Operational Consequence A category of failure consequences that do not adversely affect safety, the environment, or operations, but only require repair or replacement of any item(s) that may be affected by the failure. Operating Context The operating context is the circumstances in which a physical asset or system is expected to operate. Operational Consequences A category of failure consequences that adversely affect the operational capability of a physical asset or system (output, product quality, customer service, military capability, or operating costs in addition to the cost of repair). P-F Interval The PF interval is the time between the point at which a potential failure becomes detectable and the point at which it degrades into a functional failure. Safety Consequences A failure mode has safety consequences if it could injure or kill a human being. Safety Instrumented Function Analysis Safety instrumented function (SIF) analysis is one of the strategy development methodologies available in APM. The safety analysis team studies system-level and related assets to determine loss of containment scenarios, identify risk levels, and identify the safety provisions that protect against, or mitigate, loss of containment. Safety Integrity Level The design team assigns a safety integrity level (SIL) to each safety provision. This numeric value, usually on an ascending scale between 0 and 4, is a measure of the amount of risk inherent in the failure that the provision prevents or mitigates. The provision’s SIL is used in SIF analyses to calculate the impact of a possible failure. Safety Override A provision version’s safety override identifies the procedures that an operator or technician should follow when a safety device malfunctions in order to keep the facility operating safely while the device is being fixed or replaced. When a safety device fails, an APM user (for example, an engineer, manager, or operator) creates an override incident in the system that records the details and recommendations. Safety Provision The safety design team identifies the safety processes, systems, and procedures that prevent or mitigate hazards. Safety provisions record the actions to be performed, the checklist of items, and instructions. The provision version defines the safety override that identifies the procedures that an operator or technician should follow when a safety device malfunctions in order to keep the facility operating safely while the device is being fixed or replaced. It also defines a table of protected assets and the assets (for example, safety devices and control equipment) that protect them. The team assigns a safety integrity level (SIL) to each safety provision version. This numeric value, usually on an ascending scale between 0 and 4, is a measure of the amount of risk inherent in the failure that the provision prevents or mitigates. The provision’s SIL is used in SIF analyses to calculate the impact of a possible failure. Safety Regulation In APM, safety regulations are typically identified by reference numbers. On SIF analyses, the team identifies the related safety regulation when performing risk analysis. Scheduled Restoration/Discard A scheduled task that entails restoring or discarding an item at or before a specified age limit, regardless of its condition at the time. Strategy Development Analysis Strategy development analyses are methodologies for evaluating asset priority, defining asset functions, determining how failures occur (failure modes), evaluating the risk of asset failure, and preventing or mitigating the effect of failures. The varieties of strategy development analysis include: • Asset Prioritization Analysis • Current Practice Review (CPR) • Design FMECA • Reliability Strategy Selection (RSS) • Maintenance Task Analysis (MTA2) • Reliability Centered Maintenance (RCM2) • Risk-based Inspection (RBI) • Safety Instrumented Function (SIF) Analysis • Hazard and Operability (HAZOP) Analysis Strategy Development Analysis Template A strategy development analysis template is a group of settings that can be used as the basis for a strategy development analysis (MTA2, RCM2, SIF, or HAZOP). A template identifies failure modes for a type of asset, rather than for a specific asset. Similarly, it refers to indicator templates and task templates, not to specific asset indicators and standard tasks. It includes an operating context for assets and a maintenance strategy for each of its failure modes. In addition, an RCM2 template identifies functions and functional failures. Time Between Failure The length of time between failures (TBF) is used in three ways in APM strategy development analyses: • The time between occurrences of the failure (TBF) when inspections and/or preventative maintenance are performed. This value is recorded in failure statistics. • The estimated length of time between failures (ETBF) when no preventive maintenance is performed on the asset. This value is sometimes used to determine probability of failure in risk analysis. • Estimated time between consequences (ETBC) – The time between unexpected consequences or failures when inspections and preventive maintenance are performed on the asset. APM calculates the mitigated (or residual) risk using this value when maintenance feasibility is evaluated. Unwanted Situation An unwanted situation describes the result of a hazard scenario such as loss of containment. Examples are “Explosion in venting system” and “Emission of toxic gases”. In SIF and HAZOP analyses, the team identifies an unwanted situation, along with the HAZOP checklist item and inspection regime, on each failure mode.
