Maintenance and Reliability: Prevent unplanned shutdowns for LNG liquefaction facilities
Although an unplanned shutdown is an integrated part of the operational and safety management system of an operating plant, unplanned shutdowns for a modern LNG liquefaction operating facility often become some of the costliest events for the facility owner. Each of these events negatively affects the owner’s business due to loss of production and reputation. With today’s world transitioning to green energy, the benefits to LNG owners by adopting an advanced prevention and maintenance program to prevent unplanned shutdowns are obvious and financially prudent.
Challenges in preventing unplanned shutdowns. An unplanned or emergency shutdown of an operating facility due to safety, asset and environmental risks is a necessary step for owners to take the process and equipment in emergency to a safe state. Unfortunately, unplanned shutdowns for a modern LNG liquefaction facility often become frustrating events for the owners due to loss of production, which can equate to millions of dollars daily.
Preventing unplanned shutdowns and finding effective solutions are challenges facing LNG facility owners in the following areas:
- Due to the complexity and scale of a modern LNG facility, the potential failures of all components cannot be fixed at once during a scheduled turnaround due to variations of the component failure rate. Between scheduled shutdowns, a failure will always occur at a seemingly unexpected time due to randomness or unpredictability.
- Tens of thousands of active components in an LNG facility must be maintained simultaneously and properly to sustain stable operation. The task of a facility’s maintenance team is enormous, especially when a preventive maintenance approach is used.
- Identifying the potential risk of all component failures is not an easy task during the engineering design phase. A limited number of unplanned shutdowns are initiated automatically as designed (e.g., through shutdown interlocks). The majority are initiated manually by the operator depending on situations onsite, which puts a tremendous amount of pressure on the facility’s operations and maintenance teams.
- The traditional reactive maintenance approach is less useful in preventing unplanned shutdowns because the failure and shutdown have already occurred.
- The availability of accurate equipment reliability and failure rate data is key to the success of a preventive maintenance program. Sometimes, equipment breaks down earlier than what the vendors recommended or predicted from historical data, which adds more challenges to rectifying the true turnaround intervals of the equipment in utilizing a preventive maintenance approach.
- Root causes to failures leading to unplanned shutdowns vary.
- Many unplanned shutdowns were due to design deficiency and human error, which are often nightmares to owners as they are less related to equipment aging or wear and tear. It is difficult for a plant maintenance team to tackle such failures by conventional plant maintenance approaches.
Strategies to prevent unplanned shutdowns. The prevention of unplanned shutdowns for large-scale and complex LNG facilities is more than just reducing or minimizing failures. Owners that adopt advanced prevention and maintenance programs will be the ultimate winners. While all prevention and maintenance programs share a common goal to prevent failures of equipment and reduce downtime, for an LNG facility, an advanced prevention and maintenance program should be characterized by:
- Covering the entire lifecycle of the facility—i.e., from engineering design through plant operations
- Adopting preventive and predictive approaches
- Utilizing advanced technologies in monitoring, data acquisition and data analysis and management, such as a computerized maintenance management system.
Implementing such a program requires the owner’s systematic deliberation in the choice of engineering management, asset management, and operational and safety management, including a risk management program, an engineer program or project management consulting (PMC) program, etc.
Prevent unplanned shutdowns for LNG facilities. The history of the LNG industry has shown that many costly unplanned shutdowns were rooted to hazards or faults laid in the various engineering phases—conceptual design, pre-FEED feasibility studies, FEED and EPC. Likewise, efforts made to ease maintenance and operability during the engineering phase have been found to significantly reduce a plant’s unplanned shutdowns. The prevention of unplanned shutdowns can be achieved by good engineering practices and sound equipment design—selection, specification and cold-eye review in compliance with codes, standards and regulations. Some good examples of inherently safer design include utilizing advanced technologies, proper equipment design margins, equipment spare/redundancy, multiple trains, enforcement in equipment support structures and associated piping, upgraded materials of construction, etc.
The success also depends on the planning and scheduling of all related engineering activities focusing on the prevention of unplanned shutdowns, including value engineering, alarm/trip setpoints rationalization, functional safety, risk analysis of equipment failure mode, etc. For the development of a new LNG facility, it is always a good practice to start the program early, such as in the engineering design phase. It will be beneficial to make the owner’s maintenance strategy known to all parties involved (engineering contractors, licensors, equipment manufacturers, etc.) to help prevent unplanned shutdowns, and to put relevant design requirements in the basis of design. The owner’s engineers typically play an important role in ensuring that all of these procedures align with the owner’s maintenance philosophy.
During plant operation, proper maintenance of all major equipment systems is of paramount importance to minimize the potential of unplanned shutdowns due to component wear or equipment failure. While details and techniques for implementing an advanced maintenance program may depend on the specific maintenance method chosen, in general, several steps may follow:
- Identify target equipment or systems, including those that have emergency shutdown interlocks in design, based on potential risk level of failure.
- Evaluate the current conditions of target equipment or systems based on plant monitoring data and inspection in reference to historical reliability data.
- Set maintenance priorities accordingly. If a shutdown for maintenance and inspection is unavoidable, then the scheduled shutdown interval may be re-evaluated based on the potential risk level of major asset equipment to minimize the potential risk of failure, maintenance/repair cost, and cost due to loss of production.
Sometimes, unplanned shutdowns can occur due to human error. While numerous factors can contribute to human error, the utilization of respective corrective actions and best practices can significantly reduce the failures due to human error that lead to unplanned shutdowns. For example, comprehensive training of maintenance personnel and field operators can minimize unanticipated events during plant operation involving human error, as will more in-depth familiarization in the operation and maintenance of different equipment at various working environments. GP
PETER ZHANG is the General Manager and Senior Principal Consultant at Gulf LNG Solutions in the U.S., where he provides expert solutions to customers in LNG liquefaction export facilities. Dr. Zhang has 29 yr of professional experience in leading engineering design firms, such as Bechtel and KBR, and in various engineering and supervisory positions on a variety of hydrocarbon processing projects, including serving as a Principal Process Engineer/Engineering Group Supervisor on the Wheatstone LNG Export Project. Dr. Zhang is a Texas-licensed professional engineer and holds BS and MS degrees, as well as a PhD, all in chemical engineering.
Modern society would not be possible without the use of pipelines to transport natural gas, crude oil and finished products to demand centers.
Optimizing Gas Distribution: Accounting for Changeovers, Regulators, and More
Gas distribution systems are critical to the effective operation of many industrial facilities around the world. Despite the importance of these systems, however, opportunities to improve their performance and cost-effectiveness are often missed or misunderstood. Increasing changeover pressure may seem like a good way to improve system flow, for example, but it often does so at the expense of bottled gas. Adding regulators may help you control supply pressure, but it also adds cost to your system. So, how do you know what the ideal gas distribution setup is for you?
Attend this webinar to:
- Gain a basic understanding of the fluid dynamics that affect pressure control in gas distribution systems, learning to interpret flow curves and recognize phenomena like lockup, droop, and supply pressure effect (SPE)
- Learn how inlet pressure affects regulator performance and when to specify certain regulator types and configurations to effectively control gas system pressures
Understand the inherent trade-offs between gas utilization and flow capacity and how to select both the right changeover pressure and automatic changeover panel design for your operations.
May 4, 2021 10:00 AM CDT