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PAM-based optimisation

InvensysPerformance monitoring

PAM is the management of equipment assets – in this case field devices and rotating equipment. It consists of establishing the condition of these assets by means of technology such as Hart, Profibus DP/PA or Foundation Fieldbus, and ensuring that the plant can operate and do so safely, as well as implementing ongoing measures to reduce maintenance costs. Production management bases it’s planning on PAM and the personnel required for plant operation.

Condition monitoring for rotating equipment
The PAM information chain begins with the monitoring of intelligent field devices, including rotating equipment. These can be continuously monitored by way of condition monitoring, and if any abnormalities occur, the asset management system automatically drafts work instructions for the maintenance personnel.

These instructions can then be forwarded to an asset management software program, often part of the ERP system, which will in turn generate a work order.

All that now remains is to monitor the performance of the devices and machines – performance monitoring. The rest of this article recognizes performance monitoring as a key component of an optimiser.

Before an optimisation run can be launched, the condition of all equipment must be established. This is done by obtaining the current device data, then comparing this with the manufacturer's data. If the result is positive, the actual data from the devices is compared with the target data for the plant. This comparison of actual and target data provides an initial indication of the quality of the information. The next step is to analyse the actual data to ascertain the condition of the plant.

The illustration on page 24 shows a distillation column that forms part of a plant model for an olefin plant. All devices and process control equipment presented here are mathematically described in terms of scope and function. The plant model is constructed in line with the process and allows the actual condition of the plant based on the actual data to be compared with the target condition as described by the model. The model also incorporates process-engineering dependencies that are critical for evaluating the condition of the plant.

The diagnosis of measurements and potential malfunctioning of certain devices, are tolerable under the aspect of the plant as a whole, while the concept of substitute values makes it possible to conduct an overall analysis without compromising the safety of the plant. This validation process gives plant managers enough time to establish alternative solutions if it is likely that a device will break down or the function of some components will be restricted.

Prerequisites for the validation process are information from the manufacturer, as well as the expected data compared with the actual condition of the devices, taking the process conditions into consideration. Values such as the amount of clogging at the bottom of the columns, fouling of heat exchangers and changes in the behaviour of pumps and motors are derived using the model. On the left of the illustration on page 24, the detail of the M101 motor is highlighted. There is a list of the features of this motor, for example power consumption, while the top right of the illustration shows how performance monitoring is carried out.

Calculations based on the model are performed on a case-by-case basis: when discrepancies between the actual and target values arise, the solver uses the data pool for that process control component to find a solution. The tolerance range is determined by the plant management and is based on production requirements.

PAM plus performance monitoring allows comprehensive plant assessment
Experience has shown that conducting a comprehensive assessment of petrochemical plants drawing on performance monitoring coupled with PAM helps improve plant management. The asset management approach focusing on the devices is an important part of PAM, but provides only limited information on the condition of the plant. Performance monitoring requires the advance construction of a plant model, which is time and cost intensive. However, this can be reduced by using the library functions incorporated in the majority of process control equipment and devices.

The advantage of this approach is that it considers the plant as a whole, allowing changes that affect the production process to be recognised early on and corrective measures initiated. Production planning is always aware of the actual condition of the plant and can accurately assess the safety of the plant at any given time. By adjusting utilization to the actual condition of the plant, maintenance work can be optimally planned and the majority of surprises avoided. After validation of the condition of the plant, optimisation as described at the beginning of this article is the next logical step in improving the condition and operation of equipment assets.

This article as a PDF file and further information (similar articles, technical data, direct links to the manufacturer, etc.) is available online at www.PuA24.net image caption

Model of a distillation column

Carrying out performance monitoring with the objective of comprehensively improving plant management.

About Invensys
Invensys is the world leader in industrial asset performance management, a strategy designed to help today's industrial enterprises to effectively balance the availability and utilization of their production assets to match changing business requirements. In addition to its rapidly expanding Global Solutions and Performance Management services groups, Invensys' automation businesses includes industry-leading brands such as Foxboro, Triconex, SimSci-Esscor, Wonderware, and Avantis, whose products are installed in more than 100,000 plants across the world.  These range from small hybrid and batch plants to the world's largest upstream projects, refineries, gas plants, petrochemicals plants, power plants, and pulp and paper mills.
The Invensys Group (www.invensys.com) is headquartered in London and is listed on the London Stock Exchange, with approximately 30,000 employees working in 60 countries.

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Invensys, InFusion, Foxboro, Wonderware, Triconex, SimSci-Esscor, Avantis, I/A Series, and InTouch, are trademarks of Invensys plc, its subsidiaries, or affiliates.  All other brands and product names may be trademarks of their respective owners.

Contacts:   Alison Scarrott, Ballard Communications Management,
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   Stephen Ballard, Ballard Communications Management,
   email:  This email address is being protected from spambots. You need JavaScript enabled to view it., tel:  +44 (0)1306 882288
Client Contact: Angelika John, Invensys Process Systems EMEA
 email: This email address is being protected from spambots. You need JavaScript enabled to view it. tel: +33 (0) 134432668

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