Maintenance matters

Today's control and optimisation technology can revolutionise processes and maintenance operations in the continuous and batch industries, contributing significantly to a reduction in costs over the total lifecycle of the plant.

A vital feature of this new technology is its open standards interoperability. New protocols developed by the Fieldbus Foundation (FF) for 'new age' sensors and actuators, for example, allow universal integration with traditional control systems to create a single, plant-wide S95-based manufacturing operations system (S95 is the international standard for developing interfaces between enterprise and control systems).

In such an integrated system, sensors and actuators become information servers, providing measurement values and essential information about the status of the process and the field devices themselves.

By virtue of a strict mandatory interoperability test regime, FF technology guarantees that the format for communicating device parameters has been standardised. The central system device configuration tools can therefore give access to devices from different vendors.

Today it is possible virtually to eliminate the costly routines of unnecessary preventive maintenance. Proactive diagnostics can now be used throughout a plant, controlled centrally or remotely. The process and diagnostics information generated is used to make the hundreds of automated and informed decisions that have altered the traditional role of maintenance.

Nowhere is the importance of maintenance greater than in the realm of safety. Here, the new technology gets closer than ever before to 100% security with automated shutdowns possible on alarm & event (A&E) warning data. This enables safety-critical processes to take place continuously, with minimised regular maintenance drop-outs and virtually eliminating unscheduled shutdowns.

The adoption of FF technology can also have a significant effect on capital expenditure (Capex). By increasing the power and functionality of field devices, many arithmetic and related functions can be migrated from old style DCS-based systems to more modern solutions, such as Yokogawa's Centum CS 3000. But by far the most significant savings are in operation and maintenance expenditure (Opex).

The most common maintenance strategy in industry is to carry out preventive maintenance at scheduled intervals. As a result, inspections are done too early, or sometimes too late, leading to unnecessary replacements, failures and shutdowns.

A recent report by industry analyst, ARC, on the maintenance expenditure of a large petrochemical company showed that 19% of the total maintenance budget was spent on field devices (excluding valves) - of which 35% went on routine checks.

Often, a problem in the plant was attributed to a specific field device, and consequently a high proportion of the budget (28%) was spent on 'no problem found' work. Some 60% of the maintenance spend on field devices (12% of the total) went on routine checking and unnecessary inspections.

FF technology effectively eliminates routine checking and unnecessary inspections by using plant resource management (PRM) software to alert maintenance staff when parameters fall outside normal operating values. Maintenance becomes proactive.

The plant resource management system is totally integrated in the PAS and sits on top of the field device maintenance server database. It is PRM that enables multiple users on the automation system network to access all information as required. The PRM vertically integrates with plant information management systems (PIMS) and ERP programs such as Maximo or SAP.

PRM abilities are at the heart of efficient field device management. For the first time, a computerised maintenance management system such as Maximo can issue work orders triggered by real condition-based maintenance indicators, initiated by continuously running field diagnostics.

The massive flows of information generated by these systems must be well managed to prevent users being flooded with excess data and overloaded with superfluous alerts and alarms. Analysis-based definitions of filters, auto-configuring setpoints, statistical datasets, nesting and averaging are all used to manage the data and present coherent reports for the users.

This super-powerful diagnostic capability changes the role of the instrument technician, system engineer, plant engineer and operator. No longer need they do checks and recalibrations routinely at distant plant locations. Instead, they will be located centrally in an all-powerful control room - traditional monitoring is left behind as a 'knowledge-base workforce' is created.

The diagnostic functionality above is certainly state-of-the-art and is providing operational advances and business benefits for early adopters. The functionality of field devices will continue to evolve because fieldbus technology acts as an open set of protocols for just such development.

For example, the new technology of advanced function blocks is currently coming on stream. This will enable field devices to complete complex tasks, such as powerful arithmetic functions, further distributing control and increasing autonomy. Coupled with the latest flash memory EEPROM devices, new firmware can be downloaded to device memories to provide more advanced functions in installed devices. Fieldbus specifications are such that a check is performed to ensure that the download process is successful.

These procedures eliminate the need for the replacement of field devices. They can now be upgraded and reprogrammed for additional functionality.

<b>Nigel Bowden is managing director of Yokogawa Marex.</b>

Sidebar: PRM proves its worth in the North Sea

With Foundation Fieldbus technology in place, Shell's Brent Alpha platform in the North Sea is using plant resource management software as a state-of-the-art, real-time plant resource management tool. It manages all instrumentation calibration, device diagnostics, and maintenance records.

This minimises total cost of ownership and maximises total value of ownership over the platform's life cycle.

In this cutting-edge installation, a central control room is remotely located on Brent Bravo, providing remote operation of the totally automated sister rig, Brent Alpha.

The core of Brent Alpha's new control and safety system is the integrated production control system. This is a modern distributed control system (DCS) that integrates high reliability with an open environment to facilitate integration with enterprise resource planning (ERP) and manufacturing execution systems (MES).

Brent Alpha relies on a ProSafe-SLS safety system, which is in use at more than 70 Shell installations, and on the Brent Alpha platform is used to provide both emergency shutdown (ESD) and fire & gas (F&G) systems. ProSafe-SLS complements the DCS, providing a complete control and safety system that can react to emergency events in milliseconds.

All safety related events are recorded with time stamps and then stored in chronological order. The Brent Bravo ESD system also uses the ProSafe-SLS module, which was modified to accept inputs from Brent Alpha so that a total remote platform shutdown can be enabled.

Sidebar: Integrated systems, integrated information

A specialist in information management systems for the process industries, Yokogawa Marex has built on its core plant information management system (PIMS) product, Exaquantum, to provide a systems development and integration capability.

Together with its management execution systems and operational excellence solutions (MES/OES), Yokogawa Marex's PIMS systems integrate data from many systems in a plant to produce high value business information for use by decision makers at all levels of the enterprise.

The PIMS/MES/OES systems automatically integrate data from process control systems, including DCSs and PLCs, with other data from quality, maintenance, laboratory, planning, scheduling, enterprise resource planning (ERP) and many other systems. In short, Yokogawa Marex's PIMS/MES systems convert plant data into business information.