Ageing and obsolete control systems at a US-based producer of general and speciality grade polymers, was negatively affecting both throughput and the quality of blends. When Moore Process Controls approached the client, the die was cast for the move to an upgraded system.
Uwe Kurfurst, general manager, Moore Process Controls, explains that the batch reactor on the plant was running on a PLC installed in 1986, together with an obsolete HMI computer. This combination was limiting the complexity of the batch blends required and retarding the time taken to produce batches.
After an initial meeting in November 2015 to discuss the advantages of upgrading the control system, it took a further seven months to get all parties on board with the proposed solution. The decision was taken to replace Reactor 4, with the option to conduct upgrades on the remaining reactors at a later date.
Bret Stevenson, who was responsible for spearheading the project, says that the client requested an increased quality level of each batch. One of the issues with the existing system was that in some instances, and under certain conditions, a fairly high number of batches were considered ‘off-spec’. This meant that small portions of these off-spec batches needed to be blended back into subsequent batches to ensure acceptability according to quality requirements. The aim was to reduce the amount of re-blending needed and this could only be achieved if more batches were of a high enough quality from the outset. Other client requirements were that the system needed to allow for increased production to over four batches a day, and there needed to be a decreased reaction time.
The Moore solution
Moore’s solution comprised a Rockwell PlantPAx PLC, FactoryTalk View Studio SE HMI, FactoryTalk Batch, FactoryTalk Historian SE, FactoryTalk VantagePoint EMI and a ControlLogix L-Series controller. “The project was designed using the ISA-88 standard for batch systems and a detailed and well-organised simulation code was developed to test the control and batching logic in strict accordance with the client’s specifications and I/O list,” says Stevenson.
He points out that all PLC and batching code was validated on a digital twin before being implemented onsite and Moore’s engineers supplied, configured and implemented the PlantPAx PLC onsite. Concurrently, a batch reporting system was supplied to provide detailed batch reports for the tracking of raw data.
A kick-off meeting was held onsite before any work commenced and regular site meetings took place once simulation began. In addition, progress meetings were conducted remotely twice a week to ensure that all project parameters were adhered to. “We provided regular progress reports and used internal systems to measure and report back to the client, thereby avoiding any issues that could possibly have arisen,” adds Stevenson.
A challenge faced by the Moore team was that because this was an old plant, many of the connection and electrical drawings were missing. “Ideally if one is conducting a rip and replace or upgrade project, it is desirable for all documentation to be made available,” explains Kurfurst. “For the next reactor we would conduct an extensive site survey and would assemble all information prior to the project kick-off. We would also work closely with the client’s production team to better ascertain the intricacies of the specific production line’s operation.”
Kurfurst concludes that the increased number of batches, as well as the enhanced quality with minimal re-blending now required, is testament to both the superiority of the system design as well as the admirable team effort.
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