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| Functional and economical advantages of retrofits in machines and plants | | New technology for proven systems | New purchase or retrofit, i.e. partial or complete modernization - economy plays a key role in this decision. A retrofit is often much more economical than a new purchase in cases where the mechanics of older machines are still in a good to very good condition but the automation and drive technology is no longer state-of-the-art.
Retrofitting with a new control and drive technology can even breath new life into aging systems, providing astonishingly increased performance and precision. The rule of thumb is that retrofitting amounts to about 20 to 60 % of the costs of a new purchase depending on the scope of performance. At the same time, a well-planned, gradual retrofit concept enables plants to be modernized almost without downtimes.
In addition, existing investments can be used for longer with a retrofit because only those parts of a machine or system are renewed which are actually out of date. The principle processes in many industries change in time and the machines are very robust so that they may last for several decades. The mechanical side does not develop as dynamically as the electrical and automation technology. In addition, plants often hold enormous productivity reserves which can be used with state-of-the-art control and drive technology.
For example, a retrofit of a calendar (roller system consisting of several stacked heated rollers) can do more than merely restore its original performance capacity. Thanks to a more precise control and regulation, two-figure productivity increases can be achieved and significant energy savings made depending on the drives. Much higher product qualities can also be achieved. Modern, variable-speed, three-phase current motors without carbon brushes, for example, run virtually without maintenance and a lot more precisely than conventional DC motors. Depending on the type of application, up to 50 % of the energy can be saved by changing over to variable speed operation with frequency converters such as the Sinamics G150 and the strain on the system mechanics can be relieved by soft starting drives. Other advantages come into play when operating and process data are to be measured and reproduced exactly. Here, modernization of the plant creates the technical conditions for measuring these important production and manufacturing data.
Concrete examples demonstrate the benefits
At the same time, a retrofit with low-wear solutions in the automation and drive technology can bring considerable cost advantages for inspection and maintenance. For example, a retrofitting of the drives with Simoreg rectifiers and changeover from Simatic S5 to Simatic S7 in the web lines of the worlds leading manufacturer of self-adhesive, coated and synthetic leather foils saved two man days work for inspection and maintenance per six months.
In addition, the retrofit also guaranteed that the company can reliably meet todays machine and work safety standards and can cope with a greater order volume thanks to a higher workload capacity of the machines.
This example is just one of many retrofit projects which Siemens has carried out with Siemens Solution Partners in recent years. Another example of a successful retrofit in the printing industry is the modernization of an offset rotation machine in Scotland built in 1980. The machine produces about 470 million newspapers per year. By upgrading the distributed periphery to Simatic ET 200S and Profibus DP, the system owner not only achieved much higher availability but also opened the way for comfortable diagnostic possibilities which make disturbances easier to cope with. With the new Printamat Retro planning system from Siemens installed at the same time, up to 25 % start-up waste paper per order can be saved.
It was possible to save more than 60 % in comparison with a new purchase (more than 80,000 Euro) by the retrofit to a new machine tool for machining crankshafts, built in 1970. The drives were still equipped with the old DC technology and the control still programmed with the even older jumper technique (crossbar distributors) which was extremely time-consuming and work-intensive. Low-maintenance, high-precision servo drives are now in use in place of the old DC technology. The control has been re-configured based on Sinumerik 840D and commissioned together with Sinumerik Safety Integrated so that the miller additionally meets all the requirements of safety category 3 in accordance with EN 954-1.
Carding lines were modernized and restructured at a textile company. The existing automation of the machine and route control for the central fiber supply consisted of four S5-135U controllers. Release and coordination of the material transport routes were controlled by two so-called master controllers (S5-115U). The more than 10,000 inputs and outputs were controlled by a distributed periphery or by independent controllers which were linked to the central control through a bus system.
The system was changed over to Simatic S7 to be geared for the future and to have new components available for plant extensions. The distributed periphery was changed over to Profibus DP and Simatic WinCC was chosen as a user interface for the operating station. Since the familiar operating structure was simulated in WinCC, hardly any training measures were necessary for the operating personnel.
Modernization of the drive technology
Clear cost advantages due to a lower energy consumption are evident especially in the modernization of the drive technology. In a sewage works, for example, the blower control in the fermentation basin was changed over to variable speed operation with Sinamics G150 and the drive of the turbo compressor linked to the oxygen and ammonia probes in the fermentation basin by a controller. The oxygen input into the basins can therefore be controlled automatically and based on requirements by the turbo compressor. The plant owner also saves about 70 % of space thanks to the very compact C design of the Sinamics G150.
Another example of the advantages of modern drive technology can be found in a heating power station in which the two pump stations of a remote heating circuit were replaced in the course of modernization and are now driven by N-compact low-voltage motors with G150. The pumping capacity was doubled as a result.
Exact planning decisive for success
However, one aspect is of central importance in the retrofitting of a plant: the exact planning and execution on the parts of all those involved, starting with the stocktaking of the machine through technical analysis right up to detailed cost calculations. This is the only way to ensure that conversions and commissionings can be performed in the shortest time possible.
Thanks to their wide experience with the retrofitting of machines and plants and the cooperation with competent engineering partners, Siemens can also support its customer optimally in this decisive phase and create the conditions for new technology to help old plants become more efficient reliable and safe.
Advantages at a glance: Retrofit
Retrofit is to be understood as the modernization of existing production plants to increase the productivity and/or cost effectiveness to a contemporary level and delay or avoid the need for new investments and continue to operate used plants. The aims of retrofit measures are, for example:
to increase the production performance
to adapt to current work safety standards
to replace modules for which no more spare parts are available
to upgrade or modernize the automation technology
adaptations for integrating the machine or sub-plants in production systems
to save energy, e.g. by using frequency converters in electric drives
In addition, a retrofit can bring many advantages to the daily production routine:
to increase productivity by reducing standstill and failure times and by shorter cycle times
higher quality due to better accuracy and simple operation and programming
guaranteed supply of spare parts over a long period
Retrofit for DC drives
With the Simoreg DC-Master Control modules, users can equip their existing DC drive at low cost with a fully digital control and all the advantages of modern control technology. Motor, mechanics and the power unit can simply be taken over, only the control unit is replaced by Simoreg control modules.
Simoreg DC-Master 6RA70 Control Modules consisting of:
electronic box with fully digital control module
voltage detection for mains voltages from 20 to 1,000 V
pulse transformer for ignition currents up to 1 A
flexible evaluation of an external armature current actual value signal with two current converters on the mains side (phase-independent), external current converter with external rectifier or actual value signal by detection in the DC circuit
evaluation for fuse monitoring
digitally controlled field current supply up to 40 A
Migration to Simatic PCS 7
According to an estimate by analysts and experts, process control systems with an installation value of about 65 billion US dollars worldwide have reached the end of their life cycle and will have to be replaced by new technologies soon. Therefore, many companies will have to make the decision to modernize the control system now or in the near future. Main factors above all are:
danger of unplanned plant shutdowns (production failure)
expansion of business not possible without new system
no cost effective support of the installed system
old system type deleted and discontinued
existing system no longer meets current requirements
lacking reliability and consistency of the provider.
However, the complete changeover to a new control system involves considerable investments and risks. Therefore many companies aim at a migration of the systems instead of a complete replacement of the technology in this way, only the actual technology which no longer meets the requirements has to be replaced. At the same time, production failures can be reduced or avoided altogether with a sophisticated migration strategy.
This is particularly important because the life cycle of the different system components varies today between fives years for workstations via 15 years for controllers to 25 years for field and wiring. Siemens has therefore developed a sophisticated migration concept for PCS 7 with which not only control systems of different manufacturers can be migrated to PCS 7 but also individual areas of a control system such as only the HMI level can be replaced or an existing system extended by new components. This procedure reduces the risks and costs of migration.
Advance 1 / 2007 | |
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