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| By introducing a risk-based maintenance approach for BOPs, the JIP aims to spur the industry to challenge the way that maintenance on BOPs is planned and performed in the future. |
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Blowout preventers (BOPs) are a significant barrier within drilling and well control operations. A BOP can be described as a large, specialized valve assembly of several stacked blowout preventers, of varying types and functions, used to seal, control and monitor oil and gas wells.
The BOP is a key barrier toward preventing a blowout and thus reducing major accident risk. Hence, it is a very critical piece of equipment that can have a large impact on personal safety and the environment, if it is not functioning as required. Following the Deepwater Horizon incident, there is greater attention to the performance and maintenance of BOPs by both regulators and operators.
The maintenance of BOPs presents significant financial, logistical and safety implications to drilling operators and rig owners. BOPs have, traditionally, been subject to time-based maintenance, which can create critical challenges, such as introducing critical failures through unnecessary maintenance of equipment or failing to maintain the equipment at the right time.
A key driver for avoiding BOP downtime and reduced reliability is frequent testing and maintenance of components. If maintenance and testing frequencies can be decreased, without reducing the reliability and safety of the BOP, there will be a clear advantage in terms of performance and availability. Currently, an accepted, systematic approach to developing a risk-based maintenance and testing program for BOPs does not exist within the industry.
MAINTENANCE STRATEGY
There is a common understanding and expectation by the industry today, that to achieve and keep the required safety level and integrity of the BOP, the original equipment manufacturer (OEM) maintenance recommendations should be followed. Generally, these recommendations have not been challenged or changed.
OEMs are responsible for designing and producing the drilling equipment, which is then delivered to the operators. Technical experience and operational information, such as performance data, degradation mechanisms and failure rates, is captured mainly by the operators. These data could provide significant input to OEM maintenance plans, but they are not shared normally, leaving little room to predict or optimize the maintenance program. Ultimately, this means that the maintenance and follow-up activities do not take the specific applications or operating history into account, leading to OEMs providing conservative recommendations, based on a “to be on the safe side” strategy.
For example, it is generally accepted that the failure rate will increase for “dirty” service, such as milling operations. This also relates to changing out components at fixed intervals. The changing of components should occur, based on the condition of the part. Yet, it is, instead, based on the pre-defined interval recommended by the OEM. This is not just a potential waste financially; it also can impact safety by undermining the integrity of the system, due to the early “infant mortality” failure of the new/changed components (which can be as high as 60% to 70%).
CLASS RULES FOR MAINTENANCE
Ships or mobile offshore units classed by a classification society shall, as part of the class society proceedings, be subject to periodic surveys, in accordance with the requirements set by the class society rules. This is done to confirm that the hull, machinery, equipment and systems remain in satisfactory condition, and in compliance with applicable rules for classification, as well as international industry standards and flag/shelf state requirements. This action is performed traditionally through surveys at fixed intervals that include visual inspections, examinations, verifications and testing in the presence of a surveyor from the society.
As an option, the class societies have other survey arrangements, allowing for an alternative review, ensuring equivalent safety level and integrity. For machinery, equipment and systems, this typically can be the use of an approved, planned maintenance system (PMS), with maintenance tasks and intervals based on OEM recommendations.
Current regulation proposes the use of alternative methods for time-based maintenance. One example is the Petroleum Safety Authority of Norway (PSA), which has focused on drilling contractors’ maintenance functions, thereby increasing industry understanding of risk and condition-based maintenance, using the Reliability Centered Maintenance (RCM) analysis process. The U.S. Bureau of Safety and Environmental Enforcement (BSEE) is also drafting new rules for BOPs, aiming to boost their capabilities and increase assurance that they will work in an emergency.
The risk-based maintenance approach aims to mitigate the issues that arise from OEM recommendations. Benefits include increased safety and operability by improving BOP performance and increasing maintainability. This, ultimately, will deliver more optimal maintenance planning, thereby reducing costs.
At DNV GL, this arrangement is called PMS RCM (planned maintenance system–reliability centered maintenance) and allows the owner company to arrange surveys as part of its planned maintenance system. It is based on analysis of applicable functions onboard the vessel. PMS RCM is a survey arrangement, based on a review of the company management, RCM analysis and the implemented maintenance system.
The arrangement was developed initially, due to demand from the industry/rig owners for the company to provide an alternative to the use of OEM recommendations, and make it possible for rig owners to develop their own maintenance programs, based on experience, with a clear focus on function criticality. PMS RCM applies the IEC 60300-11 standard as a reference for the RCM process. This standard ensures the integrity of the process and defines the required elements needed to achieve a result acceptable to the class society.
The survey arrangement is applicable to all main class machinery items and can also be applied to vessels with additional class follow-up on drilling and/or production systems. There are a few limitations to what can be included here, one being the well control system, together with the BOP. The reason for this is there is no recognized or established practice on how to perform a RCM analysis on a BOP. To include this element in the arrangement, a guideline must be developed that outlines the process, defines a typical BOP system and functions, and also provides guidance on how this can be applied in a RCM analysis process.
To mitigate these challenges, the company has launched a new joint industry project (JIP) for risk-based maintenance of BOPs.
A JIP FOR MAINTENANCE
In recent decades, a new maintenance philosophy has been applied in the oil and gas industry, which evolved from traditional, reactive calendar-based maintenance toward a more proactive, risk-based approach. Risk-based maintenance has been introduced already across many parts of the industry, with positive improvements on safety performance and cost efficiency, and is supported by national regulations and class survey arrangements (PMS RCM survey arrangement in the DNV GL class).
By introducing a risk-based maintenance approach, using a well-established RCM methodology, with focus on performance and condition monitoring on applicable functions, maintenance of BOPs will be based on actual conditions and risk impact. To achieve this, the industry needs to come together and share its knowledge and experience. Design data need to be shared by the OEM, and full operational data need to be more transparent between the operator and owner of the equipment. Together, it will be possible to establish an alternative to BOP maintenance that increases system dependability, reduces overall maintenance costs, increases the efficiency of overhauls and increases safety levels by applying a more optimized, efficient, planned maintenance effort.
DNV GL has, together with the industry, performed a study demonstrating the feasibility of a risk-based maintenance program for BOPs. The project applied proven techniques, such as Failure Modes Effects and Criticality Analysis (FMECA) and RCM to test the feasibility of establishing a risk-based methodology.
The JIP will benefit partners and industry by enhancing knowledge of BOPs, and offers the potential to further improve the monitoring of equipment condition. The JIP will contribute to:
- A cost-efficient maintenance program, based on condition and risk, instead of a time-based one;
- Improved BOP performance (improved safety performance and production availability;)
- Optimized scope of a five-year, Special Periodic Survey (SPS) for BOPs;
- Optimized maintenance between SPS’s.
The initiative aims to provide a recommended practice or international standard, within which appropriate maintenance requirements and methods will be identified, and a cost-benefit analysis of these tasks will be evaluated.
THE WAY FORWARD
By introducing a risk-based maintenance approach for BOPs, the JIP aims to spur the industry to challenge the way that maintenance on BOPs is planned and performed in the future. Several BOP manufacturers, operators, rig owners and shelf state regulators have joined the JIP already. They are confident that the introduction of a risk-based maintenance approach will have the same positive effect, as observed in the oil and gas industry generally. For BOPs, it is expected that the maintenance activities in-between periodic surveys, as well as the scope of the periodic surveys, will be optimized with associated decreased cost, increased availability and uptime. 
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