Plant operators can improve plant maintenance strategies by implementing a well-structured, integrated, and comprehensive approach to equipment reliability called "enterprise asset performance management" (EAPM).
This approach requires that operators manage an asset to ensure that it meets the functional requirements expected of it across its entire life span.
ExxonMobil Corp.'s deployment of an EAPM system in all of its refining, chemicals, and production affiliates has helped the company reduce maintenance costs by 30% and increase mechanical availability by 2%.
In its simplest form, EAPM includes:
- Equipment strategies that ensure an asset will meet performance expectations at lowest life-cycle cost.
- Strategy execution.
- An equipment taxonomy that allows consistent asset reliability and maintenance performance.
- Selective use of key performance indicators that compare actual asset performance to expected performance.
- Decision-support tools that evaluate asset performance, identify and prioritize improvement opportunities, and support business decision making.
- A well-managed change process to revise strategies when the initial or current approach does not achieve desired results.
Equipment taxonomy
Operators must integrate asset management into the workplace to be able to predict production. Equipment taxonomy helps this integration because it allows the operator to compare data from a particular piece of equipment with consistent data in other areas, zones, sites, operating companies, etc., that use the same taxonomy.
Taxonomy is the science of consistently classifying a group or subgroup of objects. In EAPM, the term commonly refers to:
- Relationships of equipment to other equipment categories or families. This is expressed in a relational grouping of equipment classes (equipment class hierarchy).
- A classification of asset-related standard observations and activities for each event.
- Standardized key performance indicators that allow a comprehensive evaluation of people, processes, and operational performance, which are consistent across the site and within regions, business lines, companies, etc.
This equipment classification enables plant operators to achieve better results from reliability initiatives such as root-cause analysis, statistical forecasts, system modeling, and reliability-centered maintenance.
It also gives employees at different locations a common language and the ability to compile information across many different business units.
ExxonMobil taxonomy
ExxonMobil determined that it needed a corporate taxonomy, used internal subject-matter experts in its development, and deployed it with measurable increases in equipment reliability.
Over the last 10 years, ExxonMobil Research & Engineering worked with the ExxonMobil business units in chemicals, refining, and upstream to develop a standardized method for classifying, measuring, and tracking equipment specifications and performance across worldwide operations (Fig. 1).
Before ExxonMobil developed the consistent corporate taxonomy, most of its plants had maintenance management systems that did not efficiently use equipment reliability and maintenance data. The company had trouble consistently measuring equipment reliability and maintenance performance across the entire corporation.
The system ExxonMobil installed allows it fully to use the computerized maintenance management systems and associated data analysis tools. All of ExxonMobil's regions, affiliates, and individual facilities can sort, analyze, and use a large pool of consistent maintenance data to support drive improvement activities in accordance with the expectations of regional reliability and maintenance-management systems.
The EAPM interfaces with existing maintenance-management systems, as well as some older systems.
System composition
The ExxonMobil corporate equipment taxonomy is a classification of related equipment, observations, and activities ordered into a system of family groupings. Each family classification is based on common relationships, in which multiple levels of classification exist. Each succeeding level has more detail or more specific relationships of characteristics.
The ExxonMobil system includes five components: standard observations and activities, functional equipment envelopes, equipment class hierarchy, object parts and maintainable items, and technical characteristics.
Standard observations, activities
This component contains descriptive words or short phrases that consistently describe an object's condition or the maintenance work done on an object. This component includes four families:
- Functional failure describes the equipment's apparent condition that resulted in the need for maintenance. This family defines which functional performance aspect is outside of the acceptable standard of performance.
- Failure cause describes the observable cause for the failure.
- Damage describes the condition of the object, part, or assembly when maintenance was performed.
- Activity describes what was done to repair the equipment or maintainable item.
Functional equipment envelopes
Functional equipment envelopes define the process locations and equipment necessary to perform a process function.
For example, a centrifugal compressor cannot compress a gas without a driver, a gearbox, a foundation to support everything.
These and other closely bound equipments are part of the functional compressor envelope.
By aggregating event history for the process locations and equipment contained in a functional equipment envelope,
ExxonMobil performs higher-level reliability and maintenance performance analysis with key equipment performance indicators.
Equipment class hierarchy
This is a multilayered list that describes the different equipment classes in a given facility and shows how each is related.
At higher levels, a class consists of equipment that provides a similar function. How the equipment works may be different; for example, reciprocating steam pumps and centrifugal pumps are physically different, but they are both still pumps and they both provide a similar function.
In the next lower level, the primary function remains the same and how the function is performed becomes more similar.
The lowest level of business-justified differentiation describes equipment units with fairly common object parts or maintainable items and technical characteristics.
An operator can perform varying depths of performance analysis in a particular level in the hierarchy. All equipment with a unique asset or equipment number should fit into one of the classes. All maintenance work, therefore, should allocate to equipment classes that are in this hierarchy.
Object parts, maintainable items
Object parts, maintainable items are lists that identify significant components and subassemblies that make up each item in an equipment class. These components do not generally have a unique plant identifier.
When an operator performs maintenance, he selects the specific components from the object parts, maintainable items lists, and assigns standard observations and activities.
Technical characteristics
Technical characteristics contain the most frequently used technical information associated with equipment classes. Primary users of this information include maintenance personnel such as technicians, planners, and screeners, equipment engineers, and inspectors. Secondary users of the information are process and reliability engineers.
ExxonMobil's system formalizes agreement on a common list of standard observations and activities, functional equipment envelopes, equipment classes, and object parts, maintainable items, and a core list of technical characteristics common to all its businesses. This provides consistency both across a site, and within a region, business line, or company.
Multidimensional system
For ExxonMobil, the organization of equipment classes in the hierarchy and their related object parts, maintainable items, and technical characteristics define the boundaries for small, relatively discrete pieces of equipment, such as valves.
More complex equipment groups like compressor trains require functional equipment envelopes.
A centrifugal compressor train, for example, can use equipment from classes in different discipline categories, such as electrical equipment (motor driver), fixed equipment (lube oil tank, piping, valves), instruments (vibration monitoring system, sensors), machinery (couplings, gearbox), and others.
Because many equipment classes can apply to other equipment, ExxonMobil developed a multidimensional taxonomy structure of common names, terms, and actions, in addition to common groupings of functional equipment envelopes.
The taxonomy was deliberately constructed in multilayered levels to allow multilevel analysis of the same consistent data from different perspectives.
"Process location" defines a spot in the process occupied by a physical piece of equipment.
A process location corresponds to a tag number rather than an individual and specific equipment unit, which has a unique work identification number.
A process location has a unique set of attributes that relates to the required functional equipment performance, such as process fluid, temperature, pressure, and flow rate; conversely, the physical equipment asset has data associated with it, such as manufacturer, material of construction, rating, and other design details.
ExxonMobil's machinery, mechanical, and inspection engineers are the most frequent users of equipment-class level data.
Engineers can analyze event history for the equipment they know and understand, unencumbered by data regarding other equipment in the functional equipment envelope that they may be less familiar with.
Benefits
The front-end design of ExxonMobil's corporate equipment taxonomy included more than 11,000 man-hr of work.
ExxonMobil deployed the taxonomy into all its refining, chemicals, and production affiliates.
Long-standing performance criteria for individual equipment classes have changed, sometimes by factors of 5 or more, causing asset managers to establish gap-closing plans for assets once thought to have acceptable performance.
The system's common global and equipment event language improved communications and data sharing between sites and decreased data collection time. This led to improved operating performance and lower direct costs.
These improvements helped ExxonMobil reduce maintenance costs by 30% since 1996.
With the availability and visibility of company-wide standards, many ExxonMobil sites improved equipment class performance by comparing data with related consistent data from other sites.
Using internal performance benchmarks, ExxonMobil can identify and prioritize opportunities to improve performance and can allocate resources to high-value opportunities.
The authors
Michael Duell is an advanced engineering associate for ExxonMobil Research & Engineering, Fairfax, Va. He has 23 years' experience in machinery and reliability engineering with various ExxonMobil chemical, coal mining, engineering, and refining affiliates. Duell holds a BS in mechanical engineering from the State University of New York, Buffalo. He is a registered Professional Engineer in Virginia and Louisiana.
Richard Beck is the asset performance management consulting group leader at Meridium Inc., Roanoke, Va. He has 22 years' experience in inspection, maintenance, and reliability. He previously worked for Chevron Corp. and Chevron Phillips Chemical Co. LP. Beck holds a BA (1979) in education, mathematics from Mississippi State University, Starkville.