• Publicatie 8 Januari 2022



Since the late 1990s, inspection and maintenance approaches in industry have been globally moving from prescriptive, time-based towards risk-based ones. This trend has clearly been established by the wish to increase the on-stream production time, to reduce unscheduled downtime due to corrective maintenance, to avoid shutdown due to equipment failure and/or to reduce undesirable impacts on process safety. The EN 16991 Risk-based Inspection Frawork (RIBF) is intended for managers and engineers

establishing the RBIM (Risk-based Inspection and Maintenance) policies in the process, power, steel and other relevant industries. This document is intended to be used in conjunction with the relevant internationally accepted practices, national regulations and RBI company policies. The standard aims to provide a common reference for formulating the RBI policies and developing the corresponding inspection and maintenance programs.

Author:  CEN/TC 319    Source: EN 16991 Risk-Based Inection Framework

Risk-Based Inspections are carried out in discrete time steps within the life cycle of a component, structure or industrial system. In order to describe the changes within each time step a mathematical formulation of degradation (i.e. ageing) of the asset is defined.

Click to enlarge: Asset & Maintenanec Management-A time perspective by Jan Stoker 

A basic model with defined uncertainties, which is improved step by step through introduction and evaluation of new knowledge gained about a structure or system is shown below.

The ideal result is a precise assessment of the condition with reasonable margins of uncertainty. The model is able to show the successive impact during the long-term deterioration process as well as the effect of sudden changes in condition. It is recognized that the individual results from inspection and assessment will influence the quality of the prediction.

The concept is to give a common understanding on structural ageing in general, which can be incorporated into different industrial applications and adapted regarding the industry-specific demands. The degradation figure illustrates a simplistic ageing model with the uncertainty bounds around the design life of a component, structure or industrial system.



Intermezzo: The Asset Management BowTie

The recently published standard EN 17485 introduces methods and procedures about maintenance within physical asset management for all the levels and functions of the organizations’ management, including corporate planning management, plant management, technical management, production management, financial management, asset management, maintenance management, and quality management. Further and maybe even greater benefits are now being found through improved credibility in the eyes of customers, regulators and other stakeholders.

Click to enlarge

Physical asset management also results in much greater engagement and motivation of the workforce, and in more sustainable, continual improvement business processes. Physical asset management builds up the required link between maintenance management and the organizational strategic plan and gives direction to maintenance activities.The standards EN 16646 and EN 17485 build the bridge between ISO 5500x (Asset management system standards) and the EN maintenance standards. ISO 55001 states that organizations should determine e.g. the organizational context, requirements for the assets, decision criteria, strategic asset management plan and asset management plan (including maintenance).

However, it does not describe how to do it. Respectively, maintenance standards often introduce e.g. the concept of the required function or the concept of maintenance strategy, but do not explain how they have been determined. EN 17485 introduces a methodological framework which advises organizations to implement the requirements presented in ISO 55001. By doing this it creates the bridge between the several maintenance standards and ISO 5500x in order to give an applicable starting point to the more detailed documents for the specific sub-functions of maintenance (See AM-BowTie).

This insights, the Asset Management BowTie, can be added toward the Asset Management paradigm with the (Digital) Line of Sit. To add the BowTie principle, the body of thoughts of the EN-17485 can be incorporated in the Asset Management paradigm with the mentioned standards. Result is a deepened figure 1 of the ISO5500 completed with the Line(s) of Sights, the levels of information, Business, Risk Assessment and Asset & Maintenance going to decision making  in balancing Costs, Risks and Performance.

The Asset Management BowTie show how standards can be uses as a reference framework. 

Click to enlare Asset Management BowTie: See Body of thoughts AM-BowTie Click Here

All important Key Performance Indicators (KPIs) related to the aspects that potentially can have an impact on the performance or durability of a structural member are to be considered. These data sets are implemented into a probabilistic model for service life calculations of the individual items, to cover occurring uncertainties which have to be considered within the established maintenance plans in terms of lower and upper bound of service life expectancy.

The starting point of the asset’s service life is mainly based on the applied design code and the underlying safety consideration in the course of the design calculations, while the ageing process in general depends on certain major sources of impact:
– operating time since manufacture/construction;
– system robustness;
– material properties;
– type of structure.

To describe the individual deterioration process properly the following additional aspects are of relevance with regard to structural performance over time:
– direct loading frequency;
– direct loading intensity;
– quality in manufacturing;
– environmental influences (such as temperature, radiation, corrosive environment);
– chemical exposure.

The basis for the service life expectancy considerations is expressed in terms of structural conditions. After being put into operation, each member’s range of ratings represents the available (total) capacity, which is consumed over time during the entire service life.

Click to enlarge Source: EN-16991 


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