Bridging the PLANT DATA GAP

Even with the best will in the world - or the best distributed control system for that matter - many process companies are failing to make the best use of one of their most valuable assets, plant information. Most of today's leading distributed control systems (DCS) provide an archiving or `Historian' facility to store all data generated from the plant's control and instrumentation systems. But much of that data is all too soon discarded. The problem is one of storage capacity and has led to a growing market for plant information management systems.

According to David Barr, managing director of Cirencester-based Beaver Valley Systems, these systems bridge the gap between the short-term data storage of DCSs and the corporate archiving of MRP and ERP (materials and enterprise resource planning) systems.

Infrastructure product

Founded five years ago, Barr's company is the main UK distributor for the PI plant information system developed in the US by OSI Software. Originally designed for refinery applications, PI is what Barr calls `an infrastructure product' which interfaces with many other computer-based applications - not just DCSs but others too, such as maintenance management or advanced control packages - to store data, in compressed form, from all these sources.

However, as Barr estimates that some 60 per cent of a plant's information base is available from its control system, it's not surprising that the majority of PI users tend to be plants run by large DCS systems. Refineries apart, Beaver Valley's customers now include chemicals companies such as Dow Corning, Tioxide and Merck Sharp & Dohme; utilities like National Power, Eastern Electricity and Scottish Hydro-Electric; and specialist processing companies such as Alcan, BNFL and Polaroid. Not all of these rely on DCSs, however, and Beaver Valley is now gaining business from users of Scada systems such as InTouch and Fix DMacs.

A PI system resides on its own server (running on any platform, though Windows NT is rapidly becoming the customers' choice) and interfaces with information sources around the plant. There are currently around 70 different standard interfaces readily available for most DCS, PLC, LIMS (laboratory information management systems), and maintenance management systems, though Beaver Valley will readily write customised ones to order. In addition there are also standard interfaces to corporate level management systems such as SAP, enabling process data to be accessed at all levels.

OSI maintains that every PI system is unique, yet every one is identical. This paradox is best explained by looking at the client/server structure of a typical (if there is one) PI system. While the heart of the system, the data archive, resides on the server, PI Client applications allow the user to make use of that data in a range of Windows-based modules.

Each PI system is individually configured, but its underlying archiving software is not customised for each plant. Basing every system on the same software code is the key, says OSI, to a reliable and maintainable product.

PI Client software packages, on the other hand, are configurable to exactly what the customer needs. Some start small, others want plant or corporate-wide systems employing multiple data servers. Generally, systems might range from around 1000 tags or information sources, to more than 100 000 tags. But each PI system can interface to one or more real-time systems simultaneously, and can read and write to virtually any real-time device or database.

In fact, PI systems are often used to pass information from one vendor's system to another's. An example of this was Beaver Valley's work with Aylesford Newsprint on its £250 million Medway recycled paper mill. PI was put into the de-inking plant to interface Cambridge Control's DMC advanced control system to other areas of the plant, in particular a Measurex DCS system in the fibre processing plant.

Beaver Valley is currently working with Dow Corning to expand an existing PI system at its silicone production plant in Barry, South Wales. According to Dow's Bob Connell, the present PI system `pulls in data from different parts of the site', including the plant's Foxboro I/A control system, which generally only holds data for about a week.

The new PI system, with a typical 2-year storage capacity, will `include everything,' says Connell, `not just the information that engineers say they want.' All parties involved - Dow, contractor Kv+rner John Brown, Foxboro and Beaver Valley - have an input to the design of the system so that every useful piece of information that can be thought of will be gathered, stored and made accessible in what Connell calls `a one-stop shop for data'.

The `customers' at that shop - engineers, operators, managers, quality controllers and the rest - will also benefit from the standard `look and feel' of all the PI outputs. This was recently enhanced with OSI's endorsement by Microsoft of the graphical front end of the PI system, the PI-ProcessBook.

The current release of ProcessBook also includes an ActiveX Control `add-in', widening the scope of PI even further via the Internet.