Pretoria Portland Cement Company Chooses Leading SCADA System for Hercules Plant
Pretoria, South Africa – Faced with a growing market demand for cement and obsolete supervisory and control equipment at its Hercules facility, PPC decided to replace their existing 30-year-old electrical and control systems with sophisticated technology – a major upgrade that took more than a little courage and commitment.
And they did so using the number one supplier in the business, as ranked by Frost & Sullivan in 2010 – AVEVA and its Wonderware System Platform, InTouch HMI, Historian and Historian Client (trending, analysis and reporting) suite of solutions.
As the leading supplier of cement in Africa’s largest economy as well as the Southern African region, it is imperative that PPC continuously improves efficiencies at its operations to ensure that it supplies product to the market reliably and consistently. To maintain its market-leading edge, the PPC Pretoria Hercules plant went through a major overhaul. Given the extensive nature of this upgrade, it was critical that there was as little interruption as possible to the plant’s operations.
The proposal included upgrading the electrical and control systems of kiln 5 and raw mill 3 at the PPC Hercules plant. The proposal dealt with the replacing of all Motor Control Centre panels (MCCs) and Control Panels (RIO) to improve the standard of MCCs, SCADA and PLC.
In short, this meant replacing a 30-year-old control center that had served well with a new, state-of-the-art solution that is flexible and offers the best in real-time information management and optimized process control.
The pre-engineering phase involved gathering plant information to ascertain exact equipment installed, determining process flow diagrams as well as updating and redesign of electrical drawings. This enabled PPC engineers to compile a list of equipment to be replaced as well as to draw up a detailed enquiry document and functional design specification. The purpose of this exercise was to minimize any unforeseen obstacles in the tendering process and to enable potential suppliers to offer an accurate quote. A comprehensive tender document was then drawn up and given to suppliers for their consideration.
PPC chose system integrator Quad Automation for the project. “This was a multi-faceted and large project,” says Ernie Koopmans, Director, Quad Automation. “All MCCs would have to be replaced with modern switch gear as well as for the PLC and SCADA system. There was a limited version of System Platform already in place and this would have to be expanded and upgraded to the latest version.”
Challenges Faced with the Old System
Given the scale of the overhaul, management encountered various challenges with the previous, outdated system. The nature of this required a fine balance between maintaining operations and mitigating potential interruptions, while installing new equipment — an art in itself.
- Maintenance issues & obsolete equipment — Most of the electrical switchgear and instrumentation in use was obsolete compared with the technology available today. This older equipment is maintenance-intensive and causes prolonged downtime during failures, as most of the original spares are no longer available and modifications need to be done.
- Limited expansion — Existing panels have no more room for expansion or additions, hence retrofitting new equipment would incur a high level of risk. In addition, where loose- standing equipment had been introduced, irregular plant supply had been used, thereby cluttering the walls of the substations, jeopardizing the equipment installed. Any further expansion, such as the burning of secondary material, would not allow newer equipment to be fully integrated with older equipment, forcing the new expansion to run on semi-automatic with limited control.
- Inflexibility (relay control) — Any changes were difficult to implement and required extensive rewiring.
- Limited information — There was insufficient information on bin and silo levels and all damper actuators used were discontinued due to their age and spare shortages. In addition, events were not logged which meant that cause and effect scenarios could not be determined. Gathering of process information was a lengthy procedure that ended up being useless or inaccurate. This made it difficult to back track or get enough information to implement process changes successfully while gathering information such as alarm and trip settings for auditors was a challenge because there was no central storage repository for all of the information.
- Safety issues (compliancy) — The status of power distribution in the plant was unknown in many cases while some field instruments and relays were filled with liquid mercury, which is hazardous to the environment and health of workers.
- Nuisance trips — Some temperature devices were hardwired together in order to give temperature differences. When one of the devices failed it had an influence on one or more devices causing inaccurate readings and unnecessary trips. Also, there were process lines and equipment that had been decommissioned, but not taken out of the circuit. However, some of these interlocks were still working, causing a high risk of unnecessary stops and trips.
- Limited data acquisition capability — Much of the data was read off chart recorders (provided they hadn’t run out of ink).
Project Goals and Requirements
To address these challenges, the project would have to be ambitious, radical and have the least possible impact on production at the Hercules plant. This would entail the following:
- Establishing a centralized control room — There would be no more isolated sources of data.
- Ensuring the effective measurement of KPIs, logging and trending — For example, cement production is a significant contributor to global fossil carbon emissions (figure 3). Bearing in mind the impact of cement production on the immediate environment, PPC situated the plant as far from Pretoria as possible in 1892. Today, PPC Hercules has been swallowed up by the greater Pretoria metropolitan complex, making its dust management that much more meaningful.
- Installing a distributed PLC network (based on Profibus) and remote I/O capabilities.
- Translating the old system into PLC / SCADA control — Although this sounds obvious, the implementation is not. “And it wasn’t just the hardware,” says Koopmans. “Perhaps the greatest challenge was migrating operators who, for decades, have known exactly which button to push under given circumstances to an environment that takes all that away but still needs their understanding of the process.”
- Adding a new Historian server — Some standards had already been established with the existing but under-utilized System Platform-based system.
- Upgrading all AVEVA licenses.
- Replacing all redundant electrical equipment.
- Installing new instrumentation.
It was planned that approximately 60% of work would begin in January 2010, inclusive of MCC manufacture, new cabling and cable racking. MCC and I/O panels were manufactured off-site with FAT testing being overseen by PPC to ensure that the equipment would be ready for commissioning on delivery. As far as possible, new instruments were also installed, but only powered-up on commissioning.
Disconnection of old MCCs took place during the planned Girth Gear replacement in July 2010. Installation of new MCCs, remote I/O panels and connection of new cabling took place during this shutdown.
The System Platform Galaxy status shows that 101 templates were used for 3364 instances (objects, motors, dampers, valves, analogues, etc.). “The idea was to minimize template design while maximizing instance design to make it a manageable environment,” says Koopmans. “Also, standardizing displays and icons contributed towards a greater level of operator acceptance and buy-in. This included simulating the analogue displays of the old system which they were used to as well as filtering alarms such that they were meaningful and prioritized.”
- Achieved PPC objectives within time and budget constraints
- Upgraded to the latest release of System Platform seamlessly, which made best use of the existing investment of PPC
- Operator buy-in, early ownership and easier change management through the ability to change the system to their liking cost-effectively
- Working library and structured standards based on best practices will save PPC from expensive experimentation in future upgrades
- Four-screen design and navigation standard saves operators running around the plant as they can see everything at a glance and navigate to the necessary information easily
Replacing aging control systems with modern technology is a complicated process because it means reinventing and reinstalling the control structure of processes that keep the company ticking. This means interfering with the company’s core business operations. When manufacturing companies undertake major upgrades and improvements, it is a process that is planned well in advance before engineering even begins. But, like death and taxes, that decision is inevitable and with today’s technology and system integrator knowhow, it is easier for companies to upgrade now than in the past. The alternative is, well, there really isn’t one.