Undoubtedly, the last three decades have seen the progressive affirmation of the Simatic S5 programmable controllers, as one of the most used automation solution, proved to be as one of the most reliable, durable and with high popularity, as a further confirmation that at that time, Siemens held a more than only significant PLC market share. On the other hand, the technology continues to evolve, also favored by the introduction of the latest technological innovations, new circuits arrangement, availability of more performant and fast microprocessors, and the improved reliability of the rest of the used electronics, reasons for which, understandably, it cannot be ensured the prolonged survival of a past product family, characterized by outdated architecture, design and performances.

In this context, while considering such remarkable success (and it is precisely for this reason that the manufacturer has ensured so prolonged longevity for the Simatic S5 series), some time ago (1994), Siemens has introduced a new series of programmable controllers, called Simatic S7, which as per original plans, should have replaced, gradually, the outdated  Simatic S5 series.  On the other hand, of course, the adoption of the technology implied by the most recent series Simatic S7, will ensure not only the use of products made according to the latest manufacturing standards (eg, more respectful to the environment), but also a wider range of features, easier integration of the controlled production area (in respect to the automated factory in which it will operate), greater flexibility about the I/O and communication modules available, as well as new display and storage capabilities.

In contrast, continue to use products based on Simatic S5 series, implies at least the following issues:
  - poor system optimization due to reduced availability of S5 skilled programmers;
  - gradually reduced reliability, due to parts with many hours of work;
  - poor not upgradable performances, sue to obsolete technology;
  - possible prolonged production stops due to a difficult recovery of spare parts;
  - maintenance budget costs progressively increasing.

To the above scenario, it should be added that Siemens has now discontinued the production of the Simatic S5 series in the years between 2003 and 2006 (see below chart), and the related spare parts will be available until 2015, then, the Simatic S5 series will definitely be considered as obsolete.

    

In addition, it is also necessary to take into account the typical life expectancy of any electronic device, or perhaps, more effectively, to evaluate realistically, the chances of failure that may occur, that progressively will affect its reliability, due the increasing aging of the equipment itself: the greater the age, the higher will be, understandably, the percentage of failure that will result. The side picture, shows a typical example of this operating trend, in respect to the equipment age. 

Bearing in mind these aspects, probably will be convenient to consider the possibility of a production unit (or machine) complete renovation, inclusive of its automation and control section, or, in case of the general mechanics conditions are still pretty good, it may be possible to limit the renewal action to its automation and control section only (better if inclusive of its complementary electromechanics, drives, etc., especially when also these equipment are obsolete too) as such revamp action will allow to avoid such mentioned issues, performing a possible migration of the control system from previous Simatic S5 systems to the new Simatic S7 series.

It should be noted that the new Simatic S7 series is in no way compatible with the previous Simatic S5 series, either in hardware or in software. Furthermore, although the programming software Step 7 provides a sort of "macro" that may enable conversion from Step 5, in almost all occasions, this conversion still has to be revised, modified and optimized manually, both, because the new software Step 7 is structurally different in its features (for example, type of available blocks are different, several organizational blocks were removed and their original features are now accessible directly,  the maximum length of a block is changed, as well as the number of segments and the instructions per segment, etc..), and also because any type of pre-existing HMI type feature (OP panels), communication with supervisors, or specific (such as a technological module for control of positioning), would now be made ​​with completely different cards, featuring from different ways of setting and usability (eg different communication protocol), which necessarily must be reformulated as a new software, to be revisited and adapted to the Step 7 standard requirements.

Further additional detailed information may be got by the  Siemens's Simatic S5 to S7 migration brochure, that can be downloaded here: simatic-s5-s7-migration.pdf.

Migration from Simatic S5 to S7 then, is an operation not without its difficulties also because, due to the very long period of time during which have been created such installations based on the use of this series of controllers, aspects like the followings must be taken into account:

  - unavailability of the technologist of the machine or of the automated process;
  - very often software developed at that time, has no documentation or printouts;
  - often the software resides on the RAM of the CPU, held only by the battery;
  - your Simatic S5 PLC is currently online and is working under production.

Not least, due the undisputed longevity of this series, it shall be taken into account that many of the systems installed, are definitely foregoing with the latest regulations related to safety at work (e.g. the Machinery Directive 2006/42/EC), and therefore as a fact, they no longer complies with such current legislation. For these reasons (which sometimes may even outweigh the simple need to migrate from old series Simatic S5 to the new Simatic S7), it becomes very urgent to proceed with the complete renovation, or at least with the control and automation section of it, in order to incorporate new additional protections and the management of new levels of emergency and emergency stops for the machine, implied by these latest regulations. In this direction, an independent body appointed by the Client, through which a first report draft on risk assessment, including all counter-measures and precautions required for the full consolidation of adequate security conditions, and the consequent process of upgrade and full conformity retrofitting. Obviously, in restoring the old Step 5 software to the new  Step 7 standard, it may be groped the integration of new levels of security management and emergency stops handling, as well as adding additional inputs originated from such new emergency commands and any additional security devices (e.g. signals from light barriers, optical curtains, etc.).

For the foregoing therefore, while offering significant advantages, migration from a  Simatic S5 system to S7, must be addressed properly, without improvising, in a manner dictated by both the specific application situation, as also by the engineers experience and competence, in order to reduce any error chances to acceptable rates.

Then it shall be verified the true status of the field, the condition of sensor devices installed and at last the real condition of the cables that interconnect the automation system with all controlled devices. Recovery of existing wiring, or the arrangement of a new one (disconnecting the existing), may proceed also by the use of some interface tools made ​​available by Siemens, suitable to make compatible the connectors of the old modules Simatic S5, with the latest S7 modules (the figure at right, for example, shows digital card connectors on the PLC S5-135/155U, connected, via adapters,  directly to comparable PLC S7-400 digital cards). These special interfaces may be temporarily used during testing of the Step 7 converted software (and then leave the final connections to take place), or, where appropriate, these may also be kept connected permanently.

First of all, therefore, a site survey will be desirable, where the production unit (or machine) operated by the Simatic S5 controller is installed, in order to recover all the available documentation (downloading also a copy of the software currently in use on the PLC CPU).  Then it will be possible to proceed with a thorough assessment of the documents retrieved (endorsements), considering what this actually represents the real state of system (as-built documentation status, of course, would be the best), and a detailed analysis of the installed hardware and its actual conditions. These activities are of particular importance, especially for those situations where the machine technologist or the automated process expert, that at that time, have designed the proper working procedure of the operating unit (or machine), defining the Cause and Effect Diagrams, and/or the operational sequences Flow Charts, from which it was possible to draft the PLC internal software.  Like to say, for such circumstances, that the existing software is, in fact, the only operating track to be followed for the software conversion into  Step 7 format.

It then tries to evaluate a possible plan of action (migration project), specifically considered on the individual installation, in close consideration of its capabilities and its level of integration and coordination with any further production units and the supervision system, considering also the best possible tests techniques, on the one hand designed to allow the testing of new Step 7 software, trying to minimize the downtime, and the subsequent decommissioning of the existing and the replacement and installation of the new.

Then it shall be verified the true status of the field, the condition of sensor devices installed and at last the real condition of the cables that interconnect the automation system with all controlled devices. Recovery of existing wiring, or the arrangement of a new one (disconnecting the existing), may proceed also by the use of some interface tools made ​​available by Siemens, suitable to make compatible the connectors of the old modules Simatic S5, with the latest S7 modules (the figure at right, for example, shows digital card connectors on the PLC S5-135/155U, connected, via adapters,  directly to comparable PLC S7-400 digital cards). These special interfaces may be temporarily used during testing of the Step 7 converted software (and then leave the final connections to take place), or, where appropriate, these may also be kept connected permanently.

At this point, a comprehensive review of the entire workflow is made, and are re-checked all the operational phases, in order to make sure everything is properly planned, and are also checked the dates scheduled for the various phases of the project. Once all of these activities have been carried out, defining in fact, a feasibility study with a small basic engineering activity, it will be possible to proceed with an official quote that can realistically be considered as reliable, both for costs as for planned time schedule. Where necessary, these activities also incorporate additional measures to be prescribed by the external resource that will handle the adaptation of the operating unit (or machine), the most recent safety regulations at work, and therefore, provide for our offer will include, as the final crowning goal of our works, the joint review, facing the functional testing Check List, which will be drafted by that Client's external resource.

Below is given a "gallery" referred to the main logic controllers of Simatic S5 series, together with the Step5 programming units, just in case these pictures may help you to identify any equipment in your hands: clicking on the icons, you will have access to a magnification of such small pictures.

	Click over any of the side icon in order to get a bigger photo....

Obviously, we remain at your disposal for any further information: contact us to check our current availability and our costs, without any obligation for your site.