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Strategic Asset Ageing: AIE’s Approach To Lifetime Extension Assessment

15 Jan

Introduction

The ageing of infrastructure presents a constant and growing challenge.  Ageing is characterised by deterioration which can be significant with potentially serious consequences for installation integrity if not managed appropriately; AIE however, take the view that ageing ‘per se’ has a lot less to do with the chronological age of the facilities, but everything to do with the prevailing deterioration and the rate of deterioration which may be occurring, and therefore ‘ageing’ is deemed to be a process which is common to all facilities, not just “old” ones.

We recognise that critical plant, equipment, and structures may become less reliable, obsolete or may simply be no longer fit for service as they ‘age’. The process of ageing therefore serves to increase the possibility of uncontrolled leakages and in addition, may also serve to reduce the reliability of the instrumented protective functions that are designed to control or mitigate such hazardous events.  Furthermore, conditions will change over time, and as such this will serve to change the original hazard profiles associated with the facilities.  There is therefore an obvious need to carefully consider the implications of lifetime extension in the context of installation integrity; this should involve the assessment of ‘ageing’ and the progressively changing process operating parameters with age, where the combined effects on hazard profiles should be considered in order to demonstrate continued safe and cost-effective performance during the period of extended life.

Lifetime Extension of Assets

AIE recognise the issues and challenges that are faced with the ongoing safe and reliable operation of aged assets; we would strongly contend, however, that whilst the assets may be aged, this does not mean that they are no longer serviceable.  We know that properly maintained and protected facilities may be operated safely and on an indefinite basis.  The expectation in such cases is the formal demonstration of the robustness of the aged assets where the original design lifetimes are about to be reached or have already been exceeded, in order to ensure that during the period of extended use of the assets, this does not constitute an unacceptable risk condition.

Specifically tailored and targeted asset integrity management is the key factor that is required for improved safety and asset reliability; the adoption of such an approach will invariably require a degree of inward investment but we envisage that this would readily yield the requisite production efficiencies that are central to the viability of asset lifetime extension.  AIE’s view is that through the adoption of customised AIMS capabilities the general trend of decreasing revenues and increased operational costs can be countered, adding value, and increasing the viability of the assets beyond that which would normally warrant the cessation of production, as exemplified in the illustration below.

Figure 1: Asset Lifetime Extension – Effects of Targeted Asset Integrity Management (AIM)

There are a number of elements in the ‘make up’ of an installation. The effects of ageing shall be via the evaluation of condition using methods that are appropriate to each element.

AIE Methodology – Lifetime Extension Assessment

The methodology that AIE has developed involves an engineering assessment of the design, operating conditions and history of the asset facilities that are under consideration for lifetime extension, in order to determine condition status and any specific limitations which may be deemed appropriate for the continued safe operation thereof.

AIE’s lifetime extension assessment is conducted in two discrete phases; the first is centred on establishing the current condition status by:

  1. Performing a detailed review of the key systems and their respective operational histories.

  2. Completing a detailed assessment of the current condition status of those key systems.

The second phase of the work is centred on lifetime extension assessment and involves:

  1. The review of the original design of key systems and infrastructure; this would include the consideration of the changes in the original design codes and standards since the original design was completed to determine the continued suitability for use and whether there were gaps, shortfalls or any additional requirements that may be deemed necessary, going forwards into extended life.

  2. The assessment of all credible threats and the associated risks relating to late-life operations and developing the appropriate means of monitoring the physical condition of key systems and infrastructure going forwards into late life.

  3. Assessment of the reliable operating lifetime of the key systems and the additional measures that may be required in order to satisfy the desired duration of extended operational life; this shall include, where relevant: (i) corrosion management, (ii) fatigue, (iii) general condition of fabric (iv) cathodic protection system status, and (iv)

    the identification and assessment of any other time-dependent degradation mechanism(s) which may have an effect on the operating lifetime of the systems and/or facilities.

  4. The appropriateness of the current Asset Integrity Management Strategy for the period of extended operating life and whether any amendments thereto would be necessary to reflect lifetime extension requirements.

  5. To review the safety management systems, maintenance management systems, emergency response plans and environmental procedures. These shall be reviewed for adequacy and appropriateness during the period of extended operating life.

  6. Identify any further modifications or improvements that may be required to allow the key systems to be safely operated to the revised future cessation of production date.

  7. The assessment of any relevant economic considerations, from the perspective that in the event that additional prevention, control, detection and/or mitigation measures may be required in order to satisfactorily manage the safety and risk implications associated with lifetime extension, the costs of such shall be balanced against replacement, whereupon the lower cost option is preferred going forwards (this is essentially a view of the life-cycle costs and associated risks in maintaining aged facilities in operation; the intent being to establish whether the costs of on-going operation of aged facilities is disproportionate in terms of the risks associated thereto).

  8. Obsolescence is a potential problem in late life operations; it becomes manifest when the facilities and/or systems are no longer reliable and may often be characterised by the absence of critical spares and technical support in the supply chain. The issue of obsolescence would form a key part of the lifetime extension assessment process.

The outputs from the lifetime extension assessments shall be used to formulate a detailed activity plan for the ongoing management of the facility’s risks going forward, providing that it is proven during the assessments that the risks associated with the operation of those facilities into extended life are shown to be ALARP.

 

 



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