AAOM Handbook

fatigue failure. Similar types of results can be produced in people. Some examples of potential forms of stress are; physical/mechanical, thermal, voltage, radiation, mental, etc. • Chemical - in materials science terms this would be due to the (re)action of chemicals such as oxygen, acids, alkalis, but in a broader context could also include drugs, alcohol etc. • Wear - materials science subdivides wear into different mechanisms for the removal of material, e.g. abrasion, erosion, fretting, etc. • Fouling - accumulation of material, e.g. silting, scaling, contamination, etc. • Obsolescence - this is not a category used in materials science but reflects a type of threat that arises from the loss of support for either the products or services of a process, e.g. due to innovation or competition, the imposition of constrictions to the process, e.g. imposition of new standards/laws, or the loss of essential resources for the continued operation of the process, loss of people, skills or knowledge, loss of parts sources etc. The above threat mechanisms may act either alone or in combination, and when acting in combination may produce a threat that does not occur with either of the mechanisms absent, e.g. stress corrosion cracking, the result of a combination of highly alkaline environment and high physical stress levels. The initiating mechanisms to consider when trying to identify the types of threats that may arise in or around a process are: • Design - fatigue, chemical action, wear and fouling are all, to some extent, 'designed in' to a process based on the purpose of the process and the choice of technologies for its implementation. • Operation - wear, stress and fouling can be influenced by the age of process elements, operating rates, operating conditions, feed materials, maintenance and process shutdown/start-up cycles etc. • People - the errors, omissions or deliberate actions of people, resulting in changes to operating procedures/limits or material/equipment specifications, can lead to stress, chemical action or wear. • Environment; o Commercial - innovation and competition may lead to obsolescence of product, services or technology. o Natural – e.g. flood, tornado, hurricane, volcanic eruption, earthquake, or landslide can lead to stress, erosion, or silting. o Social – e.g. social unrest or sovereign risk may lead to damage or changes to expectations, standards, laws etc. The underlying theory for the Operating Model design is that future performance will be delivered if the right work is completed at the right time and in the right way – and that this performance will be achieved more consistently, and at lower cost, if the work is planned, scheduled and resourced in advance of its execution. This theory applies equally to the Production, Service and Support work of a process.