Linde Gas AB (formerly AGA) operates an LNG (Liquefied Natural Gas) terminal in Nynäshamn which supplies the Nynäs refinery with natural gas and also has an offloading facility for liquefied natural gas to trucks. Completed in 2011, the facility is controlled and monitored by a Siemens PCS 7 system. With computers that are eight years old and a Siemens PCS 7 system that has not been upgraded since installation, it was decided that action was necessary to ensure the operation of the plant.
It was decided to replace all computers with new ones and to upgrade the Siemens PCS 7 system to the latest version. As the refinery requires uninterrupted supply of natural gas to keep production running, the replacement of computers and upgrade of Siemens PCS 7 was limited to the refinery's planned shutdowns which only occur every four years.
The planned shutdown of the refinery was scheduled for 14 days, during which time the computers had to be replaced and the upgrade of the Siemens PCS 7 system commissioned and tested. Parallel service activities on the plant will be carried out during the shutdown, which requires coordination. Existing hardware in the control system had to be retained which meant there was no parallel system to test run and no possibility to easily back out if the upgrade on site was in trouble.
During the stoppage, the truck unloader was required to remain operational with only short interruptions to download available.
- Together with the client, we drew up a detailed plan for the implementation of the work on site, including coordination with other activities.
- Contingency plans were prepared for any problems that may arise in connection with the replacement of computers and downloading to the PLC.
- The initial focus was on getting the process parts that handle car unloading operational and then gradually ensuring the operation of the rest of the process.
- Together with the project team, a successful replacement of computers and upgrade of Siemens PCS 7 to the latest version was planned and implemented. This ensured operation and delivery for many years to come.
- Thanks to careful planning, the replacement of computers and the commissioning of the upgraded control system were completed in less than a week. As a result, it was possible to deliver natural gas to the refinery with a good margin when their production started.