Ageing Plants

A Presentation of

Prepared byYousuf Memon

Yousuf Memon n

As Plant & Equipment Integrity Professional, he has been in oil & gas exploration, petroleum refineries, petrochemical plants, chemical plants, fertilizer plants, power plants, desalination plants for last several years. 

His working areas include Plant Inspection, NDT, Corrosion Monitoring, Corrosion Inhibitor Injection, Material Selection, Protective Coatings, Material Performance Evaluation, Cathodic Protection System, Risk-Based Inspection and Failure Analysis.

He has received bachelor’s degree in chemical engineering from Dawood College, Karachi in 1975 and has previously served ARAMCO (Saudi Arabia), TOTAL E&P (UAE) and PARCO (Pakistan) in various disciplines of mechanical integrity.

He delivers in-house and public seminars in Pakistan and abroad on relevant topics. He also heads operations of Reliance Swift Veritas (RSV) & Petrosult & Unimart (P&U).

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Ageing is not about how old your equipment is; it’s about what you know about its condition, and how that’s changing over time

Ageing PlantsAgeing Plants

Presentation Summarysuf Memon nManagement of plant and equipment integrity begins with an

awareness that ageing is not about how old the equipment is, but is about what is known about its condition, and the ageing equipment is equipment for which there is evidence or likelihood of significant deterioration and damage taking place since new, or for which there is insufficient information and knowledge available to know the extent to which this possibility exists.

Significance of deterioration and damage relates to the potential effect on the equipment’s functionality, availability, reliability and safety. Just because an item of equipment is old does not necessarily mean that it is significantly deteriorating and damaged. All types of equipment can be susceptible to ageing mechanisms.

Degradation mechanisms are multiple and depend on the type and quality of material of construction, the operating conditions, the process fluid, operating history, and time in service. It is, therefore, crucially required to develop countermeasures against the deterioration of equipment before it gets the critical condition.

Countermeasures include understanding the degradation mechanisms and their detection by carrying out appropriate inspection and testing.

Decision can be derived how to proceed taking into consideration the inspection and testing results for justify continued service, re-rating, repair, or scrapping the equipment.  

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Ageing is not about how old your equipment is; it’s about what you know about its condition, and how that’s changing over time

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This plant was only about 5 years old, but due to poor maintenance was stained in many locations from acid seepage

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Ageing equipment is equipment for which there is evidence or likelihood of significant deterioration and damage taking place since new, or for which there is insufficient information and knowledge available to know the extent to which this possibility exists.

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Just because an item of equipment is old does not necessarily mean that it is significantly deteriorating and damaged.

P

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All types of equipment can be susceptible to ageing mechanisms, and it is worth drawing attention to some examples. 

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By its nature, industrial equipment containing hazardous and/or pressurised fluids is exposed toconditions of stress and environment that ultimately will degrade the material fabric from its initial state.

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Damage will accumulate until the equipment reaches a state in which it is judged tobe no longer fit-for-service. Unless repaired or re-rated, the equipment may be said to havereached the end of its life.

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As damage accumulates, failure becomes increasingly probable, and if not withdrawn from service, failure of some kind will eventually occur.

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Identification of Ageingn

Addressing Ageingn

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The type of equipment and characteristics of duty can significantly influence the life. It is notunusual for machines with moving parts to degrade rapidly and to have very limited tolerance to damage and deviations from the design conditions in terms of human error or variations in process conditions.

Identification of Ageingn

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Static equipment, such as process vessels and pipes, tend to have much greater tolerance, and under arising conditions, can remain in-service for many years.

Identification of Ageingn

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As damage accumulates, failure becomes increasingly probable, and if not withdrawn from service, failure of some kind will eventually occur.

Identification of Ageingn

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Stages of Equipment Life-Cycle

Damage Types & Mechanisms

Indicators of Ageing

Inspection & Non-Destructive Testing 

Identification of Ageingn

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Four Stages of Equipment Life-Cycle:

The Stage within the lifecycle can be determined and controlled from finding out about the degradation mechanisms, undertaking assessment, monitoring, maintenance, repairs and refurbishment.

 

Identification of Ageingn

Equipment Life-Cyclen

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Four Stages of Equipment Life: Initial

Revealing inherent weakness or fault in the design, materials or fabrication.

Rapid degradation of the equipment early in life is possibleand it can progress quickly through the different Stages.

Can be eliminated with appropriate quality assurance and control.

 

Identification of Ageingn

Equipment Life Cyclen

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Four Stages of Equipment Life: MaturityEquipment is predictable, reliable.

Operating comfortably within its design limits.

Examination and inspection, maintenance and NDT are generally to confirm the basis for these assumptions, and their scope and periodicity can be risk-based.

Identification of Ageingn

Equipment Life Cyclen

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Four Stages of Equipment Life: Ageing

Equipment has accumulated some damage and the rate of degradation is increasing.

Signs of damage and other indicators of ageing starts.

A more proactive approach to equipment management, inspection and NDT is required.

 

 

Identification of Ageingn

Equipment Life-Cyclen

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Four Stages of Equipment Life: Ageing

May no longer be possible to predict the current condition or future service life.

Second hand equipment is assumed to be directly in ageing stage; unless there aresufficient historical evidence and records to demonstrate a lower risk. 

 

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Equipment Life-Cyclen

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Four Stages of Equipment Life-Cycle: Terminal

Becomes clear that the equipment will ultimately need to be repaired, refurbished, decommissioned or replaced.

Rate of degradation has become increasing rapidly and is not easy to predict.

 

Identification of Ageingn

Equipment Life-Cyclen

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Four Stages of Equipment Life-Cycle: Terminal

Guaranteeing adequate safety between examinations while keeping the equipment in service as long as possible.

Managed through making more use of on-line monitoring of the damaged areas.

 

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Equipment Life-Cyclen

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Four Stages of Equipment Life-Cycle: Terminal

A reduction of the severity of the duty, for examplereducing the pressure rating of the equipment may be another option to maximize the usefulnessbefore decommissioning.

 

Identification of Ageingn

Equipment Life Cyclen

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Can be categorized into four main types:

Wall thinning.

Stress-driven damage, cracking and fracture.

Physical deformation.

Metallurgical / environmental damage.

Identification of Ageingn

Damage Types & Mechanismsn

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Can be categorized into four main types:

Stress-driven damage, cracking and fracture.

Fatigue damage and cracking CreepStress corrosion cracking (SCC) Stress influenced hydrogen crackingBrittle fracture Ductile failure

Identification of Ageingn

Damage Types & Mechanismsn

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Can be categorized into four main types:

Physical deformation:

Dents and gouges

Buckling

Yielding 

Identification of Ageingn

Damage Types & Mechanismsn

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Can be categorized into four main types:

Metallurgical / environmental damage:

Hydrogen Embrittlement 

Identification of Ageingn

Damage Types & Mechanismsn

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An indicator of ageing is a sign or evidence that some damage has already or is about to occur.

Thought of as symptoms of ageing damage.

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Indicators of Ageingn

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Conditions or circumstances that can promote or accelerate degradation, or a lack of control, but are not necessarily sufficient for ageing to occur.

Identification of Ageingn

Risk Factorsn

 

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Inspection for damage is a key activity for all equipment containing hazardous fluids and/orPressure.

Equipment deteriorates, but inspection is important at all stages of the life cycle.

Approach to inspection will depend on the Stage of equipment life that has been reached.

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Inspection & Non Destructive Testingn

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Assessment of Fitness-For-Service

Remanent Life

Repair & Modifications

Revalidation of Equipment

Financial Criteria for Determining the End of Equipment Life 

Addressing Ageingn

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Once the existence, extent and mechanism of damage in a component of equipment have been established, a range of options is available.

These include:

Scrap and decommission the equipment

Remove the damage, with or without a repair.

Repair the component, temporarily or permanently, with or without removing the damage.

Addressing Ageingn

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Once the existence, extent and mechanism of damage in a component of equipment have been established, a range of options is available.

These include:

Analyze the margin between the component condition and minimum code specification.Undertake a fitness-for-service and/or remanent life assessment (if defect size data exists).

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Once the existence, extent and mechanism of damage in a component of equipment have been established, a range of options is available.

These include:

Change operating practices, de-rate the duty, or make favorable modifications to processconditions or chemistry.

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Once the existence, extent and mechanism of damage in a component of equipment have been established, a range of options is available.

These include:

Monitor the component to ensure that the extent and rate of the damage do not change sufficiently to compromise safety limits.

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Once the existence, extent and mechanism of damage in a component of equipment have been established, a range of options is available.

These include:

Course of actions needed will usually depend on the nature of the damage, economic factorsassociated with the operation and repair/replacement of the equipment and the costs of assessment and monitoring.

Addressing Ageingn

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Once the existence, extent and mechanism of damage in a component of equipment have been established, a range of options is available.

These include:An initial assessment of fitness-for-service can indicate the most cost effective and safest course to take.

Sometimes defects in components and welds will be attributable to manufacturing, and may show no signs of further development.

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Once the existence, extent and mechanism of damage in a component of equipment have been established, a range of options is available.

These include:The existence of stable pre-service defects does not necessarily mean that the equipment is sufficiently safe and fit for further service.

Some further action is always needed to ensure that adequate margins against failure exist.

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Also known as Engineering Critical Assessment or ECA.

Re-evaluation of the structural integrity of an item of equipment for further service, taking into account damage and deviations from design basis.

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Assessment of Fitness-For-Service (FFS)n

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Can be carried out:

During design.

During service before damage has been detected.

Once damage has been detected.

 

Addressing Ageingn

Assessment of Fitness-For-Service (FFS)n

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Some of the key factors for assessing the remanent life include:

Original design life (specified in years or number of operating cycles).

Current equipment age and condition.

How long ago the damage initated and how fast it is accumulating.

 

Addressing Ageingn

Assessment of Remanent Life

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Key factors for assessing the remanent life include:

Rate of degradation (whether constant, variable, or exponential).

Expected operating regime and degradation mechanisms.

Changes in material properties.

 

Addressing Ageingn

Assessment of Remanent Life

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Key factors for assessing the remanent life include:

Corrosion life (determined from the corrosion rate, allowance and thickness limit)

Limits determined from design.

Safety margins 

Addressing Ageingn

Assessment of Remanent Life

In

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Some of the key factors for assessing the remanent life include:

Rate of degradation (whether constant, variable, or exponential).

Expected operating regime and degradation mechanisms.

Changes in material properties.

Addressing Ageingn

Assessment of Remanent Life

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Some of the key factors for assessing the remanent life include:

Fatigue life

Corrosion life (determined from the corrosion rate, allowance and thickness limit).

Addressing Ageingn

Assessment of Remanent Life

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Some of the key factors for assessing the remanent life include:

Original design life (specified in years or number of operating cycles).

Current equipment age and condition.

How long ago the damage initated and how fast it is accumulating.

Rate of degradation (whether constant, variable, or exponential).

Expected operating regime and degradation mechanisms.

Changes in material properties.

Fatigue life (based on the S-N design or fracture mechanics).

• Corrosion life (determined from the corrosion rate, allowance and thickness limit).

• Limits determined from design or fitness-for-service assessment.

• Safety margins. 

Addressing Ageingn

Assessment of Remanent Life

In

Ageing Plants n

Some of the key factors for assessing the remanent life include:

Original design life (specified in years or number of operating cycles).

Current equipment age and condition.

How long ago the damage initated and how fast it is accumulating.

Rate of degradation (whether constant, variable, or exponential).

Expected operating regime and degradation mechanisms.

Changes in material properties.

Fatigue life (based on the S-N design or fracture mechanics).

• Corrosion life (determined from the corrosion rate, allowance and thickness limit).

• Limits determined from design or fitness-for-service assessment.

• Safety margins. 

Addressing Ageingn

Assessment of Remanent Life

In

Ageing Plants n

Some of the key factors for assessing the remanent life include:

Original design life (specified in years or number of operating cycles).

Current equipment age and condition.

How long ago the damage initated and how fast it is accumulating.

Rate of degradation (whether constant, variable, or exponential).

Expected operating regime and degradation mechanisms.

Changes in material properties.

Fatigue life (based on the S-N design or fracture mechanics).

• Corrosion life (determined from the corrosion rate, allowance and thickness limit).

• Limits determined from design or fitness-for-service assessment.

• Safety margins. 

Addressing Ageingn

Assessment of Remanent Life

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Some of the key factors for assessing the remanent life include:

Original design life (specified in years or number of operating cycles).

Current equipment age and condition.

How long ago the damage initated and how fast it is accumulating.

Rate of degradation (whether constant, variable, or exponential).

Expected operating regime and degradation mechanisms.

Changes in material properties.

Fatigue life (based on the S-N design or fracture mechanics).

• Corrosion life (determined from the corrosion rate, allowance and thickness limit).

• Limits determined from design or fitness-for-service assessment.

• Safety margins. 

Addressing Ageingn

Assessment of Remanent Life

In

Ageing Plants n

Factors for assessing the remanent life include:

Original design life (specified in years or number of operating cycles).

Current equipment age and condition.

How long ago the damage initated and how fast it is accumulating.

 

Addressing Ageingn

Assessment of Remanent Life

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Number of factors are considered for achieving a satisfactory result and the life expectancy (temporary or permanent) of the repair/modification are:

Welding.

Dimensional tolerances

Material compatibility

 

Addressing Ageing

nRepair & Modificationsn

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After temporary or permanent repairs are made, it is good practice to revalidate the equipment to ensure that the repairs have been carried out as specified and have not had any detrimental effect on integrity.

 

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Revalidation of Equipmentn

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Need for optimizing the cost of plant inspection and maintenance and repairs (IMR) and the decision of when best to replace equipment.

Addressing Ageing

nFinancial Criteria

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The End

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