Moving On Up

While multi-billion dollar, shiny new process plants are often the focus of attention for control systems vendors looking to implement their latest solutions and get consequent bragging rights over competitors and attendant media publicity, there is a significant chunk of business that often goes unheralded but contributes significantly to suppliers’ revenues and installed base footprint. That business is control systems migration.

Much like human beings, as they get older, control systems tend to suffer from “health problems”. And as devices start to malfunction or fail, finding replacement parts becomes increasingly difficult – as the original vendor may have stopped supporting the system or could have even have gone out of business altogether. Without a reliable source of parts supply, a process unit can easily grind to a halt.

Along with this issue of obsolescence, a control system that is a couple of decades old is unlikely to be able to take advantage of productivity-enhancing features inherent in today’s offerings, such as device diagnostics, ergonomic HMI and alarms, and integration to higher level business systems, to name a few.

Trigger point

“By 2005, we were facing a lot of problems with our existing control system,” explains Worawit Lerdbussarakam, vice president and deputy plant manager at TPI Polene’s cement factory located some 100 km north of Bangkok in the Thai province of Saraburi.

“That system was installed 17 years ago by the supplier of the cement plant equipment and was actually launched in the market even earlier – about 30 years ago.

“It was becoming more and more difficult to find spare parts, and even when we could find them, the price was very high. Along with the fact that our operations were starting to be affected through process downtimes, it became apparent that we needed to do something. So that is when we decided to look for a new control system.”

Worawit Lerdbussarakam is part of a company that has grown to become the third largest producer of cement in Thailand. Its history goes back to 1987 when Polene was established as a manufacturer of plastic pellets used in plastic-related manufacturing. In 1989, the company changed its name to TPI Polene, when it received a license from Thai Petrochemical Industry (TPI) to set up a cement production plant.

The three production lines – Line 1, Line 2, Line 3 – now in operation have a capacity of nine million tons of clinker (the solid material produced at the cement kiln stage) per year.

As Lerdbussarakam outlines, in economic good times, the plant’s output is destined wholly for the domestic construction market. However, the company began exporting cement products during the Asian Financial Crisis, and now, domestic sales account for around 70 percent of the business with the rest going for export to the three main markets of Bangladesh, Ivory Coast, and the US.

Transformation time

The first task of the TPI Polene project team was to select a control system vendor. As part of this process, three renowned automation companies were invited to submit bids. Selection criteria included: service and support capability, user friendliness, ease of programming, cost, and reliability. With one of the vendors’ systems judged to be overly complicated and too expensive, and another assessed to be difficult to program, that left Siemens and its PCS 7Cemat process control system in the winner’s frame.

Offered as a PCS 7 add on, Cemat software technology for operating cement plants is based on some 30 years of experience working with the world’s leading cement producers, according to Siemens. The idea behind Cemat is that cement producers can focus on optimizing the process rather than worrying about configuring control system. When TPI selected Siemens in 2005, it also became the first plant in Thailand to adopt Cemat.

With three lines and four major processes – Raw Mill, Kiln, Cooler, Coal Mill, – TPI took the decision to migrate the control system in stages. So in 2005, the kiln and cooler sections of Line 1 was upgraded to PCS 7 (version 6.1), followed by the kiln and cooler of Line 3 in 2007.

In addition, two other areas where PCS 7 now runs the show are the laboratory room – where analysis of process samples takes place, and the Waste Heat Recovery Plant – on on-site power generation facility that takes the heat produced by all three kilns to produce enough electricity to meet a quarter of the site’s power demands.

“We did not have a lot of time to perform the upgrades,” notes department manager Prasert Praechinnawong. “In fact, because we run a 24 hour operation, we had to do remove and install everything during our 30-day plant shutdown period.”

Rather than being discarded, the parts from the original control system were kept and stored away as spares for the parts of the plant that still used the old system, which was obviously a sensible decision given the difficulties TPI was having sourcing these components.

Implementation of PCS 7 necessitated the key project steps of programming, cabinet fabrication and wiring, signal test, commissioning, fine tuning, and data collection to gauge system performance upon start-up. Given all the new technology, an important element was familiarization, which was facilitated by sending project team members to Siemens in Germany for training.

As for the system architecture, at the upper level it comprises S7-400 PLCs linked on a 100 Mb/s fiber-optic Ethernet ring and connected to operator and engineering stations via hot-standby servers. Down below, the PLCs connect via Profibus DP to Siemens ET 200 remote I/O stations, which interface to the various process sensors and actuators.

New performance

Worawit Lerdbussarakam is evidently pleased when he talks about the performance of the new control system. “For Line 1, after installation of PCS 7 in 2005, we have had zero production downtime due to control system problems.

“Similarly, for Line 3, we have had no production losses (related to control system errors) since the Siemens system was implemented in August 2007. This is in marked contrast to a period in 2006-2007 when the previous control system caused 49 hours of kiln breakdown that resulted in 13,230 tons of lost clinker, which is equivalent to more than 12 million baht (US$366,000) of financial losses,” he notes.

As well as control system reliability, TPI also points to new-found software flexibility, which allows execution of a more efficient process through the programmers being able to make subtle changes to e.g. delay times. In fact, citing the case of the Line 1 kiln, Lerdbussarakam puts the increase in clinker production capacity from 7,500 to 8,600 tons/day down to versatile software as well as zero system errors.

Given the previous hassles related to sourcing spares, it is not surprising that not having to keep so many control system component parts is another thumbs up for the migration, since for PCS 7, these can be easily sourced from Thailand, Singapore, or Germany, according to Prasert Praechinnawong.

And there should be more benefits to come, as TPI says it s planning to extend the control system migration to the kiln in Line 2, to the other processes of Line 1 and Line 3 still using the old system, to the Cement Mill and the Packing Plant, and to a new Line 4. Under this plan, by 2011, the whole plant will be under the control of Siemens’ PCS 7 Cemat system and the migration will be complete.