How to Gather Prior Use Failure Rate Data
Prior use failure rate data can be built from the operating experience of devices that are associated with a Prior Use Certificate (PUC). Within Safety Lifecycle Manager (SLM), the Operate & Maintain module can automatically accumulate relevant device event information against the associated PUC as equipment operates in service.
This creates a structured connection between individual device history and model-level reliability information. Events such as demands, tests and bypasses can contribute operational data, while service and prior-use hours can accumulate as the commissioned device remains in operation.
This guide explains the SLM workflow for associating devices with Prior Use Certificates, commissioning those devices and using recorded operational events to build prior-use reliability information.
What Is Prior Use Failure Rate Data?
Prior use failure rate data is reliability information developed from operating experience associated with equipment in service. In the SLM workflow covered here, individual devices are associated with a Prior Use Certificate so their relevant operating hours and event results can contribute to the accumulated information held against that PUC.
The PUC acts as the model-level record. Multiple devices associated with the same certificate can therefore contribute information to a common body of operational experience rather than leaving reliability history isolated within individual device records.
SLM can accumulate information from events that have a pass or fail status or that affect device time in service. Examples demonstrated in the Operate & Maintain workflow include demands, tests and bypasses.
The underlying PUC records and their failure-rate fields are managed through the Failure Rate Library. That guide should be used alongside this page when configuring the model-level reliability records to which device operating experience will contribute.
Associating a Device with a Prior Use Certificate
Before operating experience can accumulate against a PUC, the appropriate device must be associated with that certificate.
Within the Operate & Maintain module, a Prior Use Certificate value can be selected against a device object. SLM uses cascading classification fields to narrow the available PUC options so that the selected certificate corresponds with the equipment.
The demonstrated workflow uses Device Function, Process Measurement for applicable input devices, and Device Type to progressively narrow the available selections. These classifications then narrow the manufacturer options and ultimately the Prior Use Certificate values available for the device.
Once the PUC is selected, the relationship between the device and certificate is established. Hours and applicable event information tracked against the device can then contribute to the associated PUC.
If the PUC-related selections made for a device differ from those inherited or selected for its parent instrument, SLM provides a notice highlighting the discrepancy so the user can review the association.
Why Device Commissioning Is Required
A device must be commissioned before it can contribute to PUC tracking. Creating the device and associating it with a Prior Use Certificate does not by itself begin the accumulation of operating experience.
Commissioning establishes that the device is in service. According to the SLM workflow, this status allows the device to begin contributing information such as service hours and prior-use hours as relevant events are recorded.
The commissioned status is established using a Service Status Change Event for the parent function that includes the device. Users can confirm the resulting status through the device Performance Data table or its service status history.
The Service Status Change Event guide explains this commissioning workflow in more detail, including how commissioning establishes the starting point for device service-hour and prior-use-hour tracking.
How Operational Events Build Prior Use Failure Rate Data
Once a device has been associated with a PUC and commissioned, its operational events can begin contributing prior use failure rate data.
As events such as demands, tests, bypasses and other applicable activities are recorded against the device, SLM accumulates information including service hours, prior-use hours, demands and failures.
This device-level information is then passed to the associated Prior Use Certificate. Where several devices use the same PUC, their applicable information can accumulate against the common certificate to develop model-level operating experience.
The process demonstrated in SLM is automatic once the required relationships and statuses are established. As applicable events are captured and finalized or approved, the resulting information contributes to the associated PUC without requiring the user to manually re-enter the same operational data into the certificate.
This makes accurate event capture an important part of the reliability-data workflow. The Logging Events guide provides additional detail on recording operational events within the Operate & Maintain module.
From Device Events to Model-Level Reliability History
The distinction between device-level and PUC-level information is important when understanding this workflow.
A device represents an individual item of equipment operating within the plant. Its record can accumulate its own operating history, including events and time in service. The associated Prior Use Certificate represents the applicable model type and can receive relevant information from devices associated with that certificate.
This means the operational experience of multiple applicable devices can contribute to a broader reliability history for the model rather than evaluating each installed device entirely in isolation.
For example, when commissioned devices associated with the same PUC accumulate operating hours and applicable event results, SLM can aggregate the relevant information against that PUC. This provides a structured basis for reviewing the experience accumulated for that model within the organisation.
The relationship should still be interpreted carefully. The existence of accumulated operating experience does not by itself determine that a model is suitable for every service or safety application. Engineering judgement, application conditions and the organisation’s qualification requirements remain important when evaluating prior-use evidence.
Tests, Demands and Bypasses in Reliability Tracking
The quality of accumulated reliability information depends on the operational events captured against the device. The transcript identifies demands, tests and bypasses as examples of events that can contribute information to PUC tracking.
Tests can provide pass/fail information associated with the performance of equipment. Demands provide another form of operating experience, while bypass events can affect the time and service history associated with the device.
These records therefore provide more context than a simple installation date. When maintained consistently, event history can help establish what happened to a device during its period in service and provide the underlying operational information used by SLM’s PUC tracking workflow.
Testing configuration is another part of the Operate & Maintain process. The Configuring Test Groups guide explains how devices can be organised for applicable testing activities.
Why Operational Reliability Records Matter
Failure-rate assumptions may originate from sources such as manufacturer information, external reliability references or established design-basis values. Operational experience provides a different source of information because it reflects equipment that has actually been placed in service.
Maintaining structured records of device operating time and applicable events can therefore provide additional evidence for understanding equipment reliability over its lifecycle. The value of this information depends on appropriate equipment classification, consistent event recording and a clear relationship between individual devices and the model records to which their experience contributes.
This operational perspective also fits within the wider SIS lifecycle. IEC 61511-1 establishes requirements covering the specification, design, installation, operation and maintenance of safety instrumented systems. Operational reliability records can support an organisation’s broader lifecycle information management, although the specific SLM PUC workflow described on this page is an MSS software workflow rather than a requirement prescribed by IEC 61511.
Maintaining this distinction is important: standards provide the functional safety framework, while the organisation determines how its operating evidence, engineering procedures and software systems are used to manage lifecycle information.
Managing Prior Use Failure Rate Data in SLM
Gathering prior use failure rate data in SLM depends on a connected sequence of records and activities rather than a single manual calculation.
The appropriate Prior Use Certificate must first exist in the Failure Rate Library. The device must then be correctly classified and associated with that PUC. It must be placed into a commissioned state, after which applicable operational events and service information can begin contributing to its tracked history.
As qualifying events are captured and finalized or approved, SLM automatically passes the relevant accumulated device information to the associated PUC. This reduces the need to duplicate operational information manually and maintains the relationship between individual equipment history and model-level reliability records.
The MSS Safety Systems solution supports the broader management of safety-system lifecycle information. Within the specific Operate & Maintain workflow covered here, SLM connects device configuration, commissioning, operational events and PUC association so reliability information can develop as equipment accumulates actual service experience.
