A. Anwer, Contributing Author, Abu Dhabi, UAE
In the hydrocarbon processing industry (HPI), if preventive maintenance is being performed and does not result in some insight related to the performance of the equipment or system, then that preventive maintenance is either not required or is being incorrectly directed. No single preventive maintenance should be conducted on any equipment or system that does not yield a required action on consecutive occasions.
Research shows that every day, preventive maintenance works are being performed throughout the HPI that result in nothing more than checked boxes, filled spreadsheets and system updates that do not yield any useful data. Revisions of these preventive maintenance works are infrequent—even adjusting the frequency of these potential revisions is rarely undertaken. This calls for optimizing the existing preventive maintenance practices and directing them towards determining real issues that can occur to a particular piece of equipment and/or system to ensure they are integral and reliable for continued safe operation.
Process safety information is a vital element of any process safety system, enabling the availability of all data related to the assets in any operating facility. The completeness of this data ensures the enhanced definition of an asset—from this point, only applicable and required preventive maintenance tasks should be performed. The lack of availability or completeness of this data can result in the definition of tasks that may be unnecessary for that particular asset.
An example of this is defining additional inspection tasks for a pressure vessel of unknown metallurgy. If an installed material is known to be resistant to a process, it can then be optimized for its inspection. Similarly, piping with unknown information about the paint under the insulation would require additional inspection. However, if correct and verified information related to a particular asset is available, preventive maintenance tasks can easily be optimized. A life-time inspection can be disregarded for a heat exchanger with corrosion-resistant metallurgy for its tubing and less-severe corrosion environment.
Any such optimization requires complete process safety information. Not all heat exchangers installed at a facility are the same type, and each should have its specific preventive checks. Complete process safety information, if available for fire monitors, would ensure that checks are performed as intended to provide assurance for their safe operation as and when needed. While collecting process safety information, the original equipment manufacturer (OEM) recommendations and other associated statutory requirements should be considered and included as part of the preventive maintenance plan to ensure safe and reliable operation. These mandatory checks, if ignored, could cause major damage in terms of health, safety and environmental, company reputation, legal ramifications and financial loss.
Historical operational and maintenance data is also important. It is vital for every facility to have access to all available verified records for preventive maintenance, as well as any analysis reports. This optimizes checks in place and helps define new ones, enhancing safe and reliable operation. With a computerized maintenance management system, the collection of these records is generally not a concern. However, the quality of the available records and analyses can present challenges.
Sometimes an analysis has not been conducted or requires verification to initiate actions to optimize preventive maintenance checks. At most facilities, when a historical data analysis is considered, it is taken as a reliability calculation. This means checking the outcome of all defined preventive maintenance checks to confirm whether they were passed, failed, or failed and fixed. This reliability check is the only thing that helps analyze how existing checks are performing. Effective plotting over the years helps optimize the requirement of that check, along with its frequency.
Plant changes play a vital role in how preventive checks are performed. With changes to an asset, the checks must be consistently assessed and revised. A change in metallurgy of a piping system could potentially eliminate the existing checks, or it may introduce more checks if the new metallurgy is inferior to the previous one. Every change made to assets and systems must be reviewed by the respective inspection and maintenance teams performing the preventive checks. A change in product feed could entirely revise the maintenance checks and routines being performed on a particular system. Any unnoticed change made without reviewing the existing preventive maintenance plan would leave the concerned party unaware of any modifications required.
Failure analysis. Actual asset failure is another area that requires reporting and analysis to ensure that the existing preventive maintenance checks are fully capable of preventing asset failure. Several leaks in a particular piping system over time could understandably reflect the quality of the inspection and maintenance being performed for that particular asset. It is possible that the inspection and maintenance of that piping system are insufficient. Heat exchanger tubes that leak frequently despite the performed inspection checks to ensure their integrity would call for a review of the preventive maintenance checks in place. Issues faced during the activation of emergency shutdown systems could require an update of the checks being performed, the implementation of a more reliable system, and/or the introduction of a plant change.
During this failure analysis, any reports of premature failures should be confirmed. Any failure that may have resulted prior to a planned check as recommended by the OEM is considered as a premature failure. Similarly, all other assets failing before their risk-reviewed and agreed inspection and maintenance date fall into the same category. The quantum of corrective maintenance performed on an asset must be assessed to ascertain the effectiveness of the preventive maintenance plans. That analysis has the potential to impel the changes and optimizations to be made.
With process safety information, historical data of preventive maintenance checks, plant changes review and actual asset failure data, it becomes simpler to plan for a review round of preventive maintenance checks and implement optimization not more than every 5 yr. A decision can be made before that if on-going data analysis indicates the need for a review. When unplanned and premature failures are reported, a review for that unit or set of assets should be done without delay. Preventive maintenance checks and optimization reviews can address real risk items and, at the same time, save the budget being spent on checks that are not yielding the intended outcome to continue safe and reliable operation. HP
Ashfaq Anwer is an Inspection Professional with 15 yr of experience in ammonia-urea complexes, petrochemical units, and oil and gas industries. He has extensive expertise in material selection, corrosion mapping and control, fitness-for-service studies, defining inspection framework and implementing inspection plans for old and new units.