PEI Civil Methodology - Background

Below follows an Introduction to the Civil Methodology that is implemented in IMS. 

Objective

The typical degradation processes affecting civil assets such as concrete and steel assets generally take decades before the overall structural integrity is compromised. This inherent property of civil assets requires a long-term vision to ensure their technical integrity is maintained at minimum costs and within acceptable risks. Reliability Centered Maintenance (RCM) is a life-cycle process for establishing and adjusting preventive maintenance (PM) requirements to maintain asset integrity and is suited to meet the varied construction material, life span and design requirements of civil assets.

Risk-Based Inspection (RBI) is a risk-based approach to inspection of static equipment and tanks in the Oil and Gas industries. This type of inspection analyses the likelihood of failures and the consequences of the same failures, to prioritize inspections. RBI and RCM studies conducted widely on static and rotating equipment and have proven their added value since their implementation in the industry.

RBI and RCM principles form the basis for the IMS Civil methodology. However, the dynamics of civil assets (longevity) differ from other plant equipment, such as pressure vessels and rotating equipment, for which the RBI and RCM methodologies were originally applied to. As the duration over which degradation processes works for civil assets is in decades rather than years, the RBI and RCM methodologies were thus enhanced to make them more applicable for Civil assets.

In the context of civil assets, reliability may be considered as the ability of the civil asset to perform its required function under given conditions over its useful asset life. RCM ensures that the maintenance requirements are based on a comprehensive and systematic approach that encompasses an understanding of how civil assets fail, the risk (consequences, or cost, of failure in combination with an evaluation of the likelihood) and the maintenance tasks that can be done to minimize failures and maximize reliability. Thus IMS PEI (Civil) provides a justification of investment costs in maintenance, seeks to optimize preventive maintenance through efficient use of resources while minimizing the risks of failure, and eliminates unnecessary Preventive Maintenance activities. By applying the principles of RBI, IMS PEI (Civil) also allows the user to focus on inspection tasks which contribute to the highest risks of failure, thus optimizing the inspection tasks and costs while ensuring integrity.Seeks to implement Optimized PM plans that are technically appropriate, feasible and economically justified. It should be noted that the IMS Civil methodology may not be effective if local authorities that have legislative jurisdiction over a facility do not accept the validity of RBI and RCM methodologies.

The main functionalities of the IMS Civil Methodology and Software are:

1. Build a register of civil assets, including their criticality and failure risk;
2. Development and evaluation of long-term maintenance plans;
3. Development of inspection plans that prioritizes condition monitoring for rational investment of inspection resources;
4. Optimization of maintenance plans based on life cycle assessment.

The IMS Civil methodology is available as part of the PEI module in IMS, i.e. IMS PEI (Civil).

Scope

Operating units usually have hundreds to thousands of Civil assets. An initial reservation of most civil practitioners when first considering implementing a proactive asset management strategy, is the time it takes to not only account for all the civil assets but to make an analysis of each one. However, this concern need not deter the implementation of a risk-based methodology for Civil, since a long-term view can be taken to address the entire list of assets.

The figure below shows a graph of cumulative risks (sorted largest to smallest) of 40 civil assets in a representative existing petrochemical facility. The graph shows that most facilities have a few high-risk items that, if reasonably responded to, will reduce the cumulative risk of the facility. Therefore, it is necessary to first screen the assets for those that represent the current and emerging highest risk to the facility (typically 10 to 20% of the total) and then only implement the risk-based methodology on them. The other assets (the majority - 80%) can be relegated to a run to failure or time-based maintenance plans, until there is time to evaluate them further.

In addition to existing and aging civil structures, the Civil methodology can also be deployed for new facilities. Here the focus should be on implementing a civil risk-based inspection plan to collect degradation information. This information can then be used to determine cost effective maintenance options.

Representative Asset Cumulative Risk Chart. A dedicated pre-screening study to highlight the critical assets, with limited effort, is often suggested to assist asset owners. Such a study may be a FAIR+ER (Focused Asset Integrity Review, Equipment Review) whereby the assets are inspected, and the relevant staff is interviewed to determine the current status of civil asset management within an organization. After the study the owner should perform a Civil study on those asset types that were revealed as critical, while simultaneously scheduling and reviewing assets in an area-by-area review.

A list (not exhaustive) of criteria is given hereafter that can be used as a guideline to screen the asset register during the area-by-area review to make a shortlist for a Civil study:

• Maintenance and/or replacement costs are high;
• Inspection is risky and/or expensive, e.g. flare asset, under water asset;
• Intensive usage, e.g. single flare asset that is used by several units (“vitals”)
• Assets with an history of problems that seem not to be solved yet (“bad actors”);
• Inspection was conducted a long time ago, e.g. more than 10 years ago;
• Asset that is in a poor condition and failure can be expected in the foreseeable future; and
• Assets identified by operations that are viewed as critical to the entire facility or to the unit (e.g. foundation of compressor, underground inlet tunnel, cooling water line tunnel).
  Equipment criticality can be used to determine the type of maintenance plan. 

Criticality matrix showing how criticality can determine the type of maintenance plan. It must be noted, however, that the Civil methodology is not a simple solution to the effective management of civil assets:

• The Civil methodology is a personnel resource intensive process especially for complex facilities with many civil assets;
• The Civil methodology can be data-intensive and in most instances the available information to decide the suitable maintenance strategy and to optimize its cost may be limited. This limitation is due to the timescale of civil asset degradation, inadequate inspection history or record keeping; and
• RCM will require a long-term management commitment to successfully develop and implement maintenance changes for the civil assets. This means ensuring that the assets continue to function to standards of performance required by its users;
• There must be an understanding of the importance and usefulness of collecting and sharing condition and failure data to support future analyses and maintenance changes.

Equipment criticality can be used to determine the type of maintenance plan.

History of the Civil Methodology

RCM has its origins in the aircraft industry and was developed as a rigorous and thorough process, an essential feature when dealing with aircraft airworthiness issues. In the late 1970s and early 1980s, asset managers in other industries recognized that RCM was equally applicable to any physical asset, not just aircraft. RCM was adopted for use in industries as diverse as power generation, transmission and distribution, petrochemical, manufacturing, mining and transport, and is now recognized as a best practice preventive maintenance methodology in nearly every major, capital-intensive industry, especially those that involve significant human safety and environmental conditions.

Historic Risk and Reliability Management (RRM) Tools:

The Civil methodology was developed within Shell in 2005 and first launched under the name Shell Infrastructure Asset Management (SIAM). This evolved into Civil RCM. With reference to table , note that Risk-Based Inspection (RBI) and Reliability-Centered Maintenance (RCM) principles form the basis of Civil RCM. Due to the strong RBI connection, Civil RCM has since been incorporated into the IMS PEI module. The rationale for the integration and modification is that the degradation processes affecting civil assets are in the order of decades while those affecting mechanical and electrical assets may be on much shorter timescales. The integration of these two processes has reduced the mentioned complexity of RCM implementation as it:

• Streamlines the process through a reduction in the number of assets involved by focusing only on the critical assets. Critical assets are defined as those that can incur significant risk, where risk is considered a product of the probability of failure, based on either a qualitative (e.g. subjective observations) or quantitative review (e.g. measurements over time) and the consequences associated with the failure. Consequences considered include safety, health, environmental and operational while damage to reputation plays a secondary role; and
• Employs risk-based concepts that assume reliability with the least investment of resources regardless of the asset’s age, since
• Risk = probability of failure x consequence of failure;
• If there is no change, the consequence remains constant throughout the asset’s life; and
• Maintenance should focus on only activities that reduces the probability of failure (based on condition / inspection data).

For new facilities where the probability of failure is relatively low, a degradation process may be monitored in intervals with the frequency of inspection and maintenance being a function of the previous state of the asset. The concept efficiently utilizes resources, as it focuses on the critical assets that are in unacceptable condition.

The Civil methodology is applied to a wide range of assets that include marine assets, stacks and flare assets, concrete & steel infrastructure, foundations, plant buildings, bridges and culverts, drainage, personal access facilities, cooling towers, anchor bolts and, roads and railways. Other civil asset types (e.g. protective paint, fireproofing, and insulation) can be considered as part of the concrete, steel or equipment and covered during a study of these assets. Note that fireproofing can also be dealt with as a Component.

Previously Civil RCM studies were mostly conducted with Word templates, in a format that enabled the development of maintenance and inspection plans. Excel workbooks were used to do the basic life cycle costing analysis to evaluate the long-term costs of maintenance alternatives (Life Cycle Costing (LCC)).

Today the IMS PEI (Civil) software has all the Civil RCM/RBI functionalities and acts as a database and calculator. Furthermore, it can be used to export data and make a report.

Maintenance and Reliability Principles

Maintaining equipment is a cost and labor-intensive activity that in some instances involves exposure of staff and the environment to increased risks. The purpose of maintenance should be to ensure that equipment, be it rotating, mechanical, civil, etc., continue to fulfil their intended function. 

A range of possible approaches to maintenance are summarized:Maintenance approaches.A site that is doing unplanned maintenance on their (critical) equipment is in the “fire-fighting mode”, whereby failures and their undesired consequences occur at random and control over the equipment is lost. History has shown that such a situation can lead to severe negative impacts to staff, the environment, and the business.

A site that can focus on preventive maintenance (PM) will be in control over the reliability and integrity of their assets and as such be able to plan the required budget and staff for keeping the plant running. The above figure indicates that for certain equipment that does not have significant failure consequences a managed run-to-failure policy is also part of a planned maintenance strategy. As such, it is important that the function and operating context of the equipment is well known and considered in the development of a PM plan . The objective is to arrive at planned maintenance tasks that are optimal in terms of budget, staff and exposure risks, as indicated in the figure below.

Maintenance effort vs. costs.The following list indicates some examples of sub-optimal maintenance performance:

• Unasserted and non-context-based tasks;
• Plan based solely on vendor recommendations, similar equipment or individual experience without any consideration to environment or current condition;
• Plan based on equipment requirements, rather than functional requirements;
• Impact of failure to the plant not considered;
• Mostly time-based tasks;
• No common understanding amongst Operations, Inspection, Engineering and Maintenance about the approach; and
• No living program in place to update PM plans regularly.

Modern views about maintenance are characterized by:

• Failure mode analysis is key to determine the PM tasks that will be effective;
• No PM plan can raise the inherent reliability level of a design;
• It is not cost-effective to develop a PM plan for equipment without considering its actual operating context; and
• Maintenance is performed to maintain a certain function, to prevent premature failures or to mitigate the consequences of failure. It is not intended to prevent the failure itself.