Condition Monitoring
This topic covers:
The basic principle is that we do not want to be looking at all our assets. In fact we only want to be looking at those assets that are going to be critical to the organization in the next ten years. It is therefore important that we determine the interval and the method by which the condition monitoring is to be carried out, keeping in mind that at all times we need to be able to justify this activity on an economic basis, for the benefits gained.
It is critical that an infrastructure or asset-based organization has a clear knowledge of the condition of its assets and how they are performing. All management decisions regarding maintenance, rehabilitation and renewal revolve around these two aspects, and an appropriate condition assessment program contributes to providing confidence that related management decisions are soundly based.
Not knowing the current condition or performance level of an asset may well lead to the premature failure of the asset, which leaves the organization with only one option: to replace the asset (generally the most expensive option!).
The unforeseen failure of an asset may also have large consequences that constitute a business risk or potential loss to the organization.
By conducting regular condition and performance monitoring exercises, maintenance strategies and/or rehabilitation strategies can be updated and refined and ultimate replacement programs can be more accurately determined. If failure is imminent, the organization will at least have time to look at options other than replacement, or else they may be able to manage the failure and reduce some of the consequences.
The benefits of condition assessment to an organization include:
- To provide an overall higher level of confidence in investment decisions relating to asset maintenance, replacement and renewal
- To have a better understanding of the condition and operating constraints of the assets that deliver services
- To realistically predict future liabilities for asset maintenance, replacement and renewal
- To vary the maintenance regime so as to minimize downtime or failure
- Flexibility in operations so as not to over-strain the asset
- To assess the risk exposure to the organization
- Improve optimized renewal decision making process and reduce life cycle cost
- Life extension of the assets through a combination of the above factors.
At a more detailed level, by performing condition assessments, the organization can expect to have the following questions answered:
- Where is the asset/component in its life cycle?
- When was the asset constructed/replaced/rehabilitated?
- What is the asset's (theoretical) effective life?
- What is the estimated residual life until replacement or rehabilitation is required?
- Has the asset been inspected and by what process?
- Can the asset's deterioration be predicted?
- Can the asset's failure be predicted?
- Can planned maintenance prevent the asset's failure or extend the time to failure?
- Can the asset be rehabilitated, and if so, at what cost?
- What level of service will the asset deliver once rehabilitated?
- Is the asset technically or commercially obsolete?
Condition assessment is one of the key inputs to a life cycle Asset Management Plan, comprising:
- Asset Register - the listing of all assets and their components, with their physical attributes, performance and capability
- Condition Assessment - the assessment of the current condition of these assets, using appropriate techniques. This allows prediction of the remaining useful life of an asset
- Intervention Strategy - the identification of the optimal intervention strategy for these assets including:
- Rehabilitation
- Protection
- Replacement
- Disposal.
Maintenance Plan - the optimal maintenance approach for these assets, including:
- Preventative maintenance schedules
- Performance based monitoring programs
- Condition based monitoring programs
- Allowances for unplanned maintenance breakdowns.
Condition assessment plays a vital part in the life cycle management of infrastructure assets of all types including:
- Electrical and electronic
- Mechanical
- Civil
- Building.
The condition assessment process develops the knowledge the organization holds on its assets and provides the information necessary for the economic justification of capital and recurrent expenditure investments.
For all assets, these investments will vary throughout their life cycle and this variation will also be significantly influenced by the criticality or the consequence of failure of the asset to the organization.
When decisions are being made on investment for assets, the greatest confidence is derived if the decisions are made using the best appropriate practice with all the required quality (accurate) data:
Confidence in the output of a condition assessment program can be determined through a Confidence Level Rating (CLR) process, which rates the confidence in the practices and data quality of the inputs.
Condition assessment provides the most significant input to the investment decision by providing the data for deciding whether and when an intervention (maintenance, replacement or renewal) is required. Combined with an understanding of the requirements of the business, regulatory and customer expectation, and application of appropriate practices and processes, the overall confidence level in the investment decision is derived. This is shown below:
An organization should aim to have all capital and recurrent expenditure reach a “confidence level” appropriate to:
- The business
- The value being invested
- The risk associated with those investments.
Significant investment can be made in condition assessment, and there are many examples of over-expenditure in condition assessment that could not be justified on economic, service or risk grounds. The key to any soundly based condition assessment program is that it delivers the outputs required in the most cost effective way. This requires that the condition assessment practices are the best appropriate to the organization, focused on extracting maximum value for each investment.
A best practice guideline:
- Describes the techniques for the condition assessment of all key asset types involved in service delivery
- Produces a process for determining the budget for the condition assessment activities, taking into account and linking to:
- Other best practice asset management techniques
- The age or condition of the asset
- The asset performance history, ie. reliability
- The asset value.
This protocol provides the organization with a basis with which to justify all of its condition assessment programs.
A best practice process flowchart for condition assessment programs is shown below:
Condition assessment processes should:
- Be capable of recognizing the degradation of an asset
- Be capable of being repeated by different assessors over time
- Be capable of allowing the comparison between different assets of a similar type e.g. Buildings, large & small
- Be an integral part of an advanced asset management process e.g. link to renewal and maintenance decision-making processes
- Allow identification of optimal intervention points
- Be capable of recognizing the key elements of the overall condition i.e. the distress modes
- Take into account the perspective of an asset's owner and users
- Be capable of accepting objective and subjective inputs
- Allow the condition assessment method to be enhanced in sophistication as required, based on the benefit cost
- Be economically viable, ie, derive sufficient return (benefit) for the cost incurred.
The condition (and performance) of an infrastructure asset does not deteriorate in direct relationship with its age, but varies with the:
- Operating environment
- Use to which the asset has been subjected
- Maintenance applied to the asset.
For a new asset, initial assumptions must be made about the effective (operational) life of an asset, as a basis for maintenance and renewal planning. This can be depicted as an asset decay profile as shown below, for any particular asset type. As an asset ages, these assumptions can be revised through condition monitoring and assessment.
Condition assessment can be used in conjunction with the decay curve to predict the remaining life of the asset. The decay curves can also be aggregated to form a profile of the entire asset portfolio.
Determining the condition of assets and ranking them in terms of their criticality factors is one of the most complex areas in asset management.
Condition assessment has two important outputs:
- The determination of residual, and therefore effective, life of an asset or component to reflect the true physical life
- The review, if necessary, of maintenance and renewal/refurbishment programs in support of optimizing the life of the asset or assuming greater risk.
The level of sophistication available in inspection of assets is increasing at a tremendous rate. Specialist products and systems are becoming available regularly, offering a wide range of condition monitoring techniques, which identify not only the failure mode but also the cause of failure.
Radical gains have been made in these areas in recent years through:
- New technology and methods of condition monitoring for all asset types, eg. vibration analysis, ground penetrating radar
- Improvements in the processes followed to better allow:
- Identifying the failure mode and the cause of failure
- Determining the most appropriate renewal action.
However, it is important that the organization considers the situation before moving from having no data at all on asset condition to attempting to implement the most advanced form of condition assessment. In many cases it may not be economically justifiable.
There are several key principles that need to be adhered to in developing suitable condition assessment and ranking processes for the organization such that:
- The processes and techniques used should evolve slowly in levels of sophistication appropriate to the needs of the organization
- The personnel involved in condition assessment should be those responsible for the assets concerned
- These personnel may require specialized training to complete or manage this process. In some cases expert advice is required
- The processes adopted should be an integral part of the overall asset management program
- The condition ranking system should be recorded complete with photographs and other advisory information, to ensure uniformity of approach and the ability to repeat at a later date
- The outputs and rankings should allow the organization to validate the condition of all asset types relative to each other, to enable the identification of critical assets. That is, the organization should be able to judge the relative merits for resource needs between:
- The various components that make up an asset or facility, for example, for a water treatment plant, the concrete structure, process equipment, control system, and access walkways
- The different types of assets for which the organization has responsibility, for example the pipelines, process units, water storages, or buildings.
Introducing condition assessment programs (CAPs) is recommended as a three-step approach:
- CAP 1 Basic (Introductory) Ranking Stage
- CAP 2 Intermediate (Expanded) Stage
- CAP 3 Advanced Stage
This approach is shown below, with the general steps to be taken at each stage.
At each stage, the process can be applied to fewer assets – those that require attention due to their deteriorated condition and/or performance, and especially those that are critical to the operation of the organization and present a risk of failure. This process is termed “filtering”, and is highly efficient as resources are applied only to those assets, which require attention to meet business objectives, after an initial assessment of all assets is made. The filtering process is shown below, using a Business Risk Evaluation (BRE) process to filter assets at each level of condition assessment.
The approach taken should accommodate the different needs that are likely to exist throughout the organization including:
- The condition of the assets
- The business environment and financial situation
- Customer expectations.
Basic asset management requires at least a simple ranking system for defining the condition of assets.
CAP 1 techniques should be applied for an initial ranking of all assets, and then higher-level techniques can be applied, as appropriate, to assets that are at an unacceptable service level and/or are critical assets.
CAP 1 Basic Assessment Model
The table below shows a condition assessment model that is suitable as an initial CAP 1 approach for an organization responsible for major groups of passive assets (eg. structures, pipe networks) as well as dynamic assets (eg. pumps, plant and process equipment).
Rating | Description of Condition |
1 | PERFECT/EXCELLENT CONDITION |
. | Only normal maintenance required |
2 | MINOR DEFECTS ONLY |
. | Minor maintenance required (5% asset value investment required) |
3 | MODERATE DETERIORATION |
. | Backlog maintenance required (10-20% asset value investment required) |
4 | SIGNIFICANT DETERIORATION |
. | Significant renewal required (20-40% asset value investment required) |
5 | ASSET VIRTUALLY UNSERVICEABLE |
. | Major replacement required (over 50% of asset value investment required) |
This model can be applied as the initial rating system for all assets. The assessment can include:
- Initial preliminary inspections
- Interview key staff / Delphi workshops to review asset histories, condition and performance
- Use asset age details and experience.
Where assets cannot be assessed visually because they are buried, concealed or in a confined/inaccessible space, ratings should be determined in consultation with staff using the Delphi workshops or other techniques.
The assessment can be done for all categories of assets.
By detailed fault analysis we can determine the increasing probability of a type of failure for a certain type of asset. As this evidence builds, we can use the total database to construct a model for the likely ramifications of the continuance of this type of failure. We can also use the database model to locate those similar assets that are liable to be at greatest risk and include those on an accelerated condition-monitoring program.
We can also use the database to identify some or all of the following activities:
Abnormal Operating Conditions
- This may apply to water mains that have suffered pumping hammer type pressures or to sections of electrical conductors that have continually suffered voltage surges or regular lightning strikes.
Environmental Conditions
- Identify assets that are affected by salt air or certain ground conditions, through an overlay of corrosion map or a geological map.
Physical Characteristics of the Assets
- Find assets of a particular type or a particular make, such as a poor quality manufacture of a water main or a low standard insulator.
This type of "what if interrogation" process allows asset managers to make sound decisions without the high cost often associated with site-based visual condition monitoring, or as in the past by "gold plating" the assets and the service they deliver to customers by renewing them well in advance of any likely failure mode.
Modern responsible asset management principles demand that we complete the works "just in time" and delay capital expenditure wherever possible, but without compromising the risks or the level of service we are offering to our customers.
This requires a pro-active environment in which problems are foreseen and quantified and adequate management responses are undertaken before the events affect the organization in any substantial way.
The implementation of a condition assessment program using the Step-by-Step process is summarized below.
- CAP 1 Assessment Level
- Confirm rating tables (1 to 5)
- Use Asset Register to prepare assessment sheets for all asset categories
- Review facility plans to identify all assets for initial inspection
- Establish checks to ensure uniformity of assessment between different personnel undertaking assessments
- Undertake initial inspections of facility, ensuring all asset groups are covered
- Conduct Delphi workshops as required to refine initial assessments in conjunction with relevant staff
- Input data collected into the appropriate software system for the analysis of each asset group. If a software system is not available, then a spreadsheet or other form of system may be developed.
- Undertake BRE 1 or criticality assessment to filter assets and identify those assets for CAP 2 assessment. This schedule should be reviewed in a Delphi workshop or interview for amendment, finalization and adoption.
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