The INEOS ChlorVinyls use of fieldbus at Runcorn

In a Euro300M project at Runcorn, INEOS ChlorVinyls updated the control system for the major production of caustic soda and chlorine to a digital fieldbus system, described at the FF General Assembly

The presentations by fieldbus users at the recent Foundation Fieldbus General Assembly in Antwerp included a paper by Paul Young, the Automation Improvement Manager at INEOS ChlorVinyls, describing the implementation and results of applying fieldbus and other new technologies in a Euro300M improvement project at Runcorn.

INEOS ChlorVinyls is one of the major chlor-alkali producers in Europe, a global leader in chlorine derivatives and Europe's largest PVC manufacturer.

Their "Genesis" project, through Fluor, was to replace the cellrooms, which produce caustic soda (1,200,000tpa) and chlorine (600,000tpa) by the electrolysis of brine.

The decision was made to adopt Foundation fieldbus communications with an Emerson DeltaV control system, and a HIMA SIS.

The site standard for instrumentation and control valves was based on Emerson equipment: 1223 fieldbus instruments were supplied, plus 143 HART instruments, for the process analysers and safety loop components.

AMS Asset Management Systems were implemented, with machinery health monitoring, to gain the benefits of predictive maintenance - the HART instruments on the SIS loops interfaced via an MTL Multiplexer.

Lastly, a Matrikon alarm management system was also installed.

INEOS ChlorVinyls had had an alliance with Emerson for many years prior to this project, dating back to the previous company names of ICI Chlorchemicals and Fisher-Rosemount.

This alliance had shown that the companies could together achieve improvements to plant performance, and also that the companies could work together effectively: INEOS ChlorVinyls had involved various DeltaV installations on site development projects.

Nevertheless there were significant potential risks in adopting the fieldbus approach to the Genesis project: notably these included the fieldbus design, installation and commissioning competence available, the risks of the new technology (such as potentially becoming obsolete, like Betamax) and the unique features of the application: what about the effects of the stray currents and magnetic fields in the cellrooms?.

There were also concerns over whether the proposed heavy fieldbus segment loading would cause slow responses, and whether there might be a loss of a segment during operation.

After initial project discussions within the project team, it was decided that Emerson had significantly more segment design experience than that available in the Fluor project team, so Emerson were asked to take on that part of the design on behalf of Fluor.

A conservative approach was adopted overall to the segment design, and a limit of typically 8 instruments per segment was imposed, with a maximum of 4 valves per segment (originally the project had planned to use 12 instruments per segment and not be limited on valve numbers).

No loading issues have been seen as a result, and there have been no losses of segments during operation.

This was commented on later in the FF meeting by John Rezabeck of ISP Chemicals in Lima, Ohio, who reported that he had not seen any loss of a segment in 6 years, with around 80 fieldbus loops operating in the field.

Significant benefits came from having 35% less instrument drawings, and the site cabling installation was 1-2 weeks quicker than a conventional time-scale.

Fault finding was faster on installation, but the installation technician skills were limited initially: however an unexpected benefit was that loose field terminals were soon identified and located, by monitoring the noise present on each fieldbus segment.

A major problem was indeed found with the stray currents from the electrolysers, which did cause the loss of a digital segment, because of the earth free installation.

This caused a major diagnostic and solution headache, because even straightforward conventional HART equipped valves would not work on this application, when trialled as a fall-back solution.

This was resolved with the help of Emerson fieldbus experts by separating the mounting of the digital valve controllers from the valve bodies, using electrically insulating materials.

Overall, the start-up and commissioning went well, the modifications needed to get the plant on-line were implemented very quickly, and the result was that the timescale to plant operation was reduced by 2 weeks.

This was just the start of the work for Paul Young, charged in his role as Automation Improvement Manager with gaining significant further performance and efficiency benefits from the new fieldbus installation and investment.

The AMS system has been extensively used during pre-shutdown and shutdown testing.

This has minimised the time spent on invasive testing, and typically shaved a week of time off the whole shutdown test programme (therefore enabling improved plant productivity).

Perceived valve issues could be correctly diagnosed using the ValveLink software, and the AMS was used to perform valve scan and set-ups, without having to send the valve away to the workshop.

This was crucial in avoiding electrolyser damage when it became evident that there were sizing issues with one valve in this section of the system.

The target set for the Paul Young as responsible for operational improvements, in conjunction with the Emerson site engineer, was to gain GBP500k of further benefit from the available system technology.

Examples of the improvements achieved with the new control system were:.

* From the AMS Alerts triggered on saturated loops, it was identified that some transmitter ranges were incorrect on the chlorine interchangers.

* The evaporator temperature was the limiting factor on high produuction loads.

* The alkaline pumps were undersized for the high load situations.

* The compressor oil heaters were always on.

* The vibration alarm limits were set too high.

* AMS ValveLink is used continuously to monitor the most critical valves.

* Prior to the first major outage since the AMS installation, it was possible to identify just 7 of the 415 valves on site as needing overhaul, based on their condition.

* Poor valve performance in operation, prior to repair and replacement in the shutdown, was able to be improved by repair tuning.

* High accumulated valve travel on other valves highlighted control problem areas, and led to control improvements.

INEOS have learned a lot from this project, not the least of which has been that training in digital systems and fieldbus must be delivered to all engineers and technicians across the site.

The anticipated risks have been avoided or overcome, and given that the risks continue to be managed, Foundation fieldbus is now the site standard and will be adopted on future projects.

Finally, the effort spent on exploitation post project has been essential to get the most benefit and value out of the information delivered by the systems.

This report on the outline of the project by Paul Young is provided by Nick Denbow of Processingtalk, based on the presentation and descriptive slides shown to the FF General Assembly in Antwerp in February 2008.

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