The compressor control upgrade project for a polymerisation plant operated by Safripol is a showcase of integrated control philosophy.
About the project
The project was initiated to replace the existing PLCs with new technology able to communicate with the Yokogawa CENTUM CS DCS via Ethernet. A single control room concept was followed in the integration of the existing DCS (CENTUM CS) for core process control with a fast STARDOM network-based control system (NCS) for high-speed compressor control.
According to Mike Dukas, a process control engineer at the plant, “Making use of Yokogawa’s different control platforms having unique specifications but the same well known look and feel operator interfaces allowed us to avoid extensive operator training, yet provided both the right control philosophy on the plant floor and made use of the existing management information software tools.”
Challenges and solutions
One of the objectives of Safripol was to avoid operator interference as much as possible in order to reduce costs and guarantee that processing could continue undisturbed after switchover.
By making use of a STARDOM hybrid controller, a single look and feel operator interface could be established, enabling the continued use of the DCS software and hardware while maintaining the PLCs’ high-speed process response.
The second challenge faced was the criticality of the compressors in the process. Stopping the compressors meant losing money. A tight changeover schedule and accurate pre-testing was essential.
“The changeover was virtually bump-less. Besides the planned mini-shutdown time, we did not experience any additional downtime. The first controller has been running now for over a year without any problems,” explains Dukas. “The first STARDOM unit was installed with the help of Yokogawa South Africa and, due to time pressure this was done without official training. Programming the controller was done with remote assistance from Yokogawa SCE in the Netherlands and Japan. The changeover took place without any failures or plant delays and was well within the planned time and budgets.”
The third objective was to make sure the new compressor control system was easy to program and maintain. This allows future expansions and modifications as well as the installation of additional units. According to Bennie Coetzer, an automation engineer at the polymerisation plant, “Even without training on the system, it is simple to find your way and start with the first steps of programming. After a 3-day training course one really feels the power and flexibility of the STARDOM system. Working with Yokogawa equipment gives me great satisfaction, because I know that if I need a solution, it only takes a phone call and the response is immediate.”
Ducas comments: “The old saying still applies – you cannot control what you cannot measure. But to get all these signals to and from the DCS using old technology, cabling, and junction boxes costs a lot of money. We decided to keep costs down by using modern technology that met all our requirements. A lot of options and product combinations were evaluated and STARDOM with Ethernet communication came out to be the best for our business.”
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