For many utilities, liquefied natural gas (LNG) is becoming an important element of a broad-based resiliency strategy. LNG has long been utilized as an energy source for peak shaving during periods of high demand. More recently, LNG has become a viable option to guard against disruptions in natural gas and electric supply.

Many LNG facilities were constructed and placed in service during the late 1960s to early 1970s. Components and assets that are key to efficient liquefaction, vaporization and storage are nearing the end of their original design lives.

One large Midwestern utility proactively anticipated this scenario at one of its largest LNG plants. Placed into service in 1973, the plant has cumulative LNG storage capacity of 2.1 billion cubic feet (Bcf) in two storage tanks.

This plant is set up to perform the full scope of LNG conversion. It runs natural gas through its pretreatment system, where moisture and pipeline impurities are stripped out. Gas is then sent through a liquefier where it is chilled to minus 260 degrees Fahrenheit (F). The resulting stream of nearly pure liquid methane is then pumped into the plant’s aboveground storage tanks, where it remains in its ultra-cold state. At times of peak demand, the LNG is pumped out of the tanks into the vaporization system, where it is heated back to a gaseous state and injected into the natural gas distribution system.

Refurbishment Program Started With Data

This critical facility was beginning to experience declining performance in its liquefaction and vaporization operations. More and more energy was required to chill the natural gas into a liquid state and then to return it to gas when needed. Such performance was a clear indicator that key pieces of equipment were beginning to wear out.

We were engaged to execute a mechanical integrity program, with the initial phase focused on a comprehensive assessment of critical equipment associated with liquefaction, vaporization and storage. Everything from pressure vessels and storage tanks to compressors, pumps, piping systems, valves, fittings and all related hardware was reviewed.

The program included a detailed analysis of each piece of equipment, assessing the anticipated remaining life of the equipment and the impact its inoperability could have on operations. This type of analysis produced a prioritized ranking of which equipment to address initially, and which equipment is expected to remain viable for longer periods.

This program coincided with an accelerated maintenance inspection program to document and test performance of everything from compressors and heat exchangers to pumps, valves, fittings and the plant electrical system. All critical components now have established inspection cycles compliant with applicable codes and procedures.

With this baseline of data, a phased maintenance optimization program is being formulated. Some equipment is recommended for phased replacement and upgrades, including piping, instrumentation and controls, and structural components. Other equipment has been identified for modified maintenance to enhance longevity. The scope also includes witnessing factory acceptance testing for new equipment and components, verifying that manufacturers have met design specifications before the equipment is shipped and installed — a step that is expected to help mitigate costly fixes after equipment is in service.

Capitalizing on Proactive Maintenance

With this assessment in hand, utility managers now have the visibility needed to plan and schedule needed improvements over a defined number of years.

A growing number of utilities are concluding that refurbishing and expanding existing LNG facilities makes sense, particularly during a time when it can be difficult to obtain approval to install new gas pipelines. By performing on-site expansions and upgrades at LNG facilities, more local supply can be readily achieved at a reasonable cost.

Engaging a third party to perform an accurate risk assessment of existing infrastructure also can improve safety while making better use of trained technicians.

Utilities know that strict safety protocols must be maintained. Workers must undergo rigorous training and periodic refresher courses to maintain required certifications and regulated compliance. With capital programs and annual O&M budgets planned in a comprehensive manner, training and certifications can be more efficiently maintained.

A proactive equipment reliability program can enable better strategic planning for every aspect of utility operations.


Learn how modifications to a Minnesota LNG facility have improved reliability.

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