Product category:
Plant- and Machine-Wide Communications
News Release from: The Profibus Group | Subject: Profibus PA and DP
Edited by the Engineeringtalk Editorial
Team on 12 July 2006
Fieldbus systems accelerate pigment
production
Production of pearl lustre pigments by the Merck plant at Gernsheim in Germany has been expanded significantly to meet the growth in demand.
Production of pearl lustre pigments by the Merck plant at Gernsheim in Germany has been expanded significantly to meet the growth in demand The pigments are used in automotive and industrial paints, as well as in cosmetics
This article was originally published on Engineeringtalk on 27 Mar 2006 at 8.00am (UK)
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The production processes involve coating of small, thin mica sheets held in a liquid suspension, with specific chemicals.
The thickness and chemistry of the coating determine the appearance and subsequent visible colour.
After harvesting the suspension, the by products in terms of waste gases and liquids need cleaning and treatment.
An earlier small plant using similar process engineering had used conventional I/O technology, but for the larger production plant expansion, a combined Profibus PA, DP and AS-I based approach was adopted on a Greenfield site.
This expansion was to involve 16 operator stations and 130 separate plant sections: each section has a control cabinet with at least one AS-I, Profibus PA and Profibus DP bus, with the relevant field devices for the section connected in a recurring topology.
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Diagnostics are key to fieldbus adoption
When Roche started construction of a new 25,000 tonne per annum vitamin E production plant in 2001 the decision was made to use fieldbus technology.
The plant is equipped with a redundant PCS7 control system from Siemens.
At the higher levels of the plant automation the process bus and the terminal bus, which carry the central servers, operator stations, engineering station and batch server, are linked to each section cabinet using Fast Ethernet as an optical ring, with redundancy management.
The control system also incorporates the waste gas and water treatment plant, and a further mica supply and storage tank 200 metres away: over 11km of glass fibre were used within the plant network.
Overall the new plant uses 500 valves on the AS-I bus, and 700 sensors and actuators on the Profibus PA.
Profibus DP is used for speed control on 420 drives.
The selection of this combination of fieldbus systems was made because AS-I is a cost effective approach for binary devices, and connection with Profibus is known to be reliable, because it is tried and tested.
Profibus PA allowed a wide selection of transmitters and equipment from many manufacturers, and in fact the hardware originated from a total of 10 different suppliers: these integrated into the system with virtually no technical difficulties.
The simplicity of the fieldbus installation led to a clear plant layout that is easily understandable, also reducing the requirement for cabling documentation and drawings.
Modern technology must be simple and easy to operate in all phases of its application, since only in this way can users reap the full benefits.
For fieldbus technology this means the demand for powerful and easy-to-use tools (ie software programmes) for the commissioning, parameterisation, ranging and maintenance of the field devices.
The control and management systems require an exact description of the data coming from the field, in the form of a "device description" to enable problem-free data exchange with the field devices.
In the case of Profibus, each device has a basic description DDBF (device database file, which belongs to each device, and comes in the form of a diskette), which contains the communications parameters in particular, but also several additional items of information, such as simple diagnostic parameters required for cyclic data communication.
For acyclic operations, such as device configuration and extended diagnostic functions, an additional form of device description has also proven successful for process automation: this is known as the EDD (electronic device description).
This allows manufacturers to describe the specific features and functions of their device and allow access to the operator tool, also by means of a data medium.
For this plant, the relevant DDBF and, with just a few exceptions, the corresponding EDD was used for all devices.
The Siemens PDM (process device manager) was used as the overall device manager, allowing engineer access to configure the devices across the plant.
This uses the device descriptions contained in the DDBFs, as loaded in the central engineering station of the PCS7 process control system: it also has access to the EDDs.
Thus the engineering station, on the network, running the PDM software, has all the information required for device management, scaling, diagnostics interrogation, all of which is available centrally at the control room and with a single tool.
The plant has been in operation now for several years, and the Profibus system has met the original expectations - the main benefit being cost reduction by improved efficiency, and improved quality of production.
The central access to all devices has revolutionised the maintenance activity, improving response times and work effectiveness.
The greater measuring ranges available from each device, and configuration for the application, has reduced the number of device types used and required on site.
Within the installation and commissioning phase it quickly became obvious that extra care was needed with grounding and shielding of the bus cabling, and this extra care has produced real benefits in reliable signal data.
The cost reduction was achieved in comparison to the original remote I/O plant: the Merck view is that the cost cutting potential from introducing new technology on any plant, and the utilisation of the technology to gain these benefits, depends on the motivation and training of staff in particular.
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