Simon Ellam, from Siemens Industry Automation, outlines a selection of the key areas that can help maximise a process plant’s operational efficiency
Operational efficiency is the ability for an organisation to execute its tactical plans while maintaining a healthy balance between costs and productivity. The economic efficiency of plant operation is a ratio of earnings and costs. All factors that contribute to this equation need to be optimised: throughput, plant availability and product quality, while factors that impact on this equation have to be minimised: operating cost and maintenance costs, energy consumption and raw material consumption, off-spec products, emissions, safety risks and environmental pollution.
There are many areas that can support efficiency objectives and process optimisation across a process plant. The following list is indicative – though not exhaustive.
Transparent Process Operation
The distributed control system (DCS) is the ‘window to the process’ – the human-machine interface. It is the central data source for information on production – from raw material supply to product delivery. The integration of the DCS into the IT processes of supply chain management is the foundation of cost transparency in production, such that the financial effect of specific operation sequences can be accounted or predicted.
Advanced Process Control (APC)
APC methods can be an essential tool to help improve operational efficiency with respect to productivity and economics, product quality, operability and availability, agility, safety and environmental issues. APC solutions can be realised much more cost effectively due to a DCS embedded implementation with standard function blocks and pre-defined wizards and templates for implementing basic APC principles.
Process plant tools can assist with the standardisation, visualisation and archiving of energy and output averages with time stamps. The plant consumption data is gathered via fieldbus and the transparency of energy consumptions is a basic prerequisite for plant energy management optimisation strategies. In this way energy management is anchored alongside the operator station and maintenance stations.
The transformation of production orders to a detailed schedule of batches on certain plant units at given starting times contains optimisation potential. Several optimisation targets have to be pursued at the same time while considering limited production resources. These can include: compliance with delivery dates and specifications of product quality; maximising capacity throughput; minimising cleaning efforts when different products are run in the same tank reactor and avoiding peak loads in energy consumption. Process optimisation tools such as SIMATIC BATCH can help with batch planning and automatic execution of planned batches.
Simulation and training
Simulation helps to increase efficiency in different phases of the plant life cycle. In the later stages of plant operation, Operator Guidance Systems (OGS) and Operator Training Systems (OTG) can be applied for operator training purposes using simulation models. It can also be utilised in operation if, for example, the evaluation of a new operation such as accelerating product grade changes or start-up and shutdown procedures need to be closely examined.
If new process plants are realised and simulation methods used from the beginning in all plant life cycles, benefits include problem free plant start up and fast and efficient commissioning. The early preparation of the operator team using a realistic simulation and the early test of DCS software also contribute to such advantages.
An OTS allows efficient and realistic operator training and repeatable training scenarios without undue safety risk.
Safety and security
Operation and construction of process plants with risk potential have to comply with the international standard IEC 615 11 for functional safety of safety instrumented systems. A ‘safety instrumented system’ is a combination of sensor, logic devices (e.g. the PLC) and actuators that detects abnormal situations and drives the process back to a safe state. To help support safety objectives in the plant, solutions such as a safety integrated approach can provide real peace of mind.
To provide standard and fail safe functions combined into a single controller and fieldbus architecture can offer economic benefits whilst actually increasing the overall safety levels of a manufacturing process.
The baseline for profitable life cycle costs is high plant availability, achieved by a robust DCS with solid application software based on standards and by preventative plant maintenance. Service costs for engineering support, maintenance and upgrades play an important role as well. Consequently, plant management should be aware that the main requirements for a comprehensive service package include: investment protection through service products; system availability by ensuring serviceability; serviceability using suitable migration concepts and clear obsolescence management linked to the market withdrawal of technical components or software versions.
A modern DCS platform such as Simatic PCS 7 comes with the lifecycle guarantee that it can be modernised and innovated without reproducing any legacy issues, so process manufacturers no longer need to feel that this is a cross they have to bare.
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