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Energy Conglomerate Maximizes Operational Capacity with AIMMS-based Maintenance Scheduling Model

maintenance scheduling

The company

Our customer is an international integrated energy and chemical company that leverages the talent and expertise of more than 34,000 people working in 37 countries. The company develops and commercializes technologies, building and operating world-scale facilities to produce a range of product streams, including liquid fuels, high-value chemicals and low-carbon electricity. They were looking for a maintenance scheduling and optimization solution.


The company’s Power Plant is the largest plant of its kind in Africa. It is powered by 18 Wärtsilä gas engines with an installed capacity of 175 megawatts (MW), using natural gas as feedstock. The South African electricity public utility, Eskom, introduced a system of opportunity for independent electricity producers to sell excess capacity on a short term basis. This provided impetus for the company to demonstrate its position as a low-carbon power producer in South Africa by contributing power to and easing pressure on the national grid. However, it’s Gas Engine Power Plant requires maintenance at very specific service intervals in accordance with the asset management plans. The duration of each maintenance interval is also dependent on the type of service being performed. Starting all 18 engines at the same time, for instance, resulted in the service schedules of all the machines coinciding. This would require a large number of maintenance teams during these service periods, but the company alone had one core maintenance team available. The company needed a solution to optimize the existing maintenance schedule of its Gas Engine Power Plant in order to successfully increase availability.


The Decision Support Group of the company was tasked to develop an application to optimize the schedule for operating the gas engines. The difference in the duration of the shutdown periods for the various service intervals made it absolutely necessary to optimize the schedule over fairly long term periods (two years or more). This long term view, combined with a mixed integer scheduling problem, formed a large problem size that would require a powerful solver. Because this application would require multiple runs by laypersons, a user friendly human interface was also necessary. AIMMS provided an ideal solution: a powerful multi-solver optimizing tool with a configurable and adaptable user interface, capable of creating powerful user friendly applications. With the help of ORTEC, an international consulting group and long-standing AIMMS partner, the company developed an application to create and optimize a maintenance schedule for the gas engine.


  • Increased electricity production during winter months by 4.6%

  • Increased operational capacity, easing pressure on the national grid during key months

  • Increased ability to meet demand

  • Adherence to service intervals

  • Optimal use of maintenance team

Solution implemented by AIMMS partner:


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