Article - Maintenance of PROFIBUS installations

Date: October 2009

PROFIBUS is a proven standard in the industry. More and more plants are completely equipped with this outstanding technology. The management of these enterprises is aware that the intelligence and diagnostics of the instruments contribute to costs saving and optimization of production automation. The grey area is the knowledge level of the maintenance technicians who need to work with this system. A lot of times their know-how has reached the limit which leads to a point that they see the installation as a 'black-box'. When a disturbance occurs, nobody knows what to do and where to start……

The black-box effect costs enterprises enormous amounts of money. If disturbances are not solved quickly, the production line is on hold and that means profit loss. PROFIBUS is the backbone of the installation and has to be the most stable element. This waste of finances can be avoided easily.

The solution is very simple; we should not forget the people on the maintenance floor. They have direct contact with this relatively new technology and must feel happy with it. This is purely a psychological matter. Many maintenance technicians have years of experience in conventional technology and are forced to step-over to PROFIBUS. Conventional technology is relatively simple, because it only relates to voltages and currents. PROFIBUS is a high-speed digital system that has to comply with lots of rules. Also test- and measurement tools are different. The multi-meter is not useable anymore and this was the tool these people have always worked with. This leads to negative communication to the outside world. The situation will get worse when the technicians do not have an electrical background.

Frequently when I’m asked to visit a factory and solve a problem, I can in most cases pinpoint the problem within a couple of minutes, while others have been looking at it for hours or days. Why? Because I know the rules and I know what to look for. In this article I will illustrate some tips and tricks to make PROFIBUS Troubleshooting and Maintenance a lot easier and more fun……..

1) Divide the installation in segments Use ProfiHubs to split the installation up in isolated segments. This guarantees that short circuits and wire breaks only have impact on 1 segment and not the entire installation. Segmentation also simplifies troubleshooting and maintenance. Because of cost issues these components are sometimes not implemented. This is a missed opportunity, because at the end the maintenance costs were higher than the initial investment.

2) Include measurement connectors
Every segment has to be equipped with measurement connectors to hook-up measurement tools. When these facilities are not integrated, the installation has to be shut-down when a measurement has to be done.

3) Up-to-date installation drawing
An up-to-date installation drawing has to be available. In a lot of cases the installation drawings are still version 1 and have never been updated. Drawings are very important for troubleshooting and maintenance. Important points for a useable drawing: addresses, cable lengths, installation order and termination resistors.

4) Investment in test- and measurement tools
Invest in tools that are required for PROFIBUS measurements. 2 types of tools are essential: A) The ProfiTrace Analyzer to verify if the communication is not showing deviations. With this tool we can detect; wrong addresses, cable breaks, instrument loss, diagnostic events, etc. B) The oscilloscope to verify the electrical signals on the cable. With this tool we can detect; EMC, reflections, many/less termination, etc.

5) Training
The last step is the understanding of the installation rules and obtaining practical experience with the required tools. To achieve this we need training. The enterprise has to invest in the education of its technicians. This investment will pay itself back within a short time.

As soon as the above points are taken care off, a successful life-cycle comes a lot closer. To conclude, the entire issue comes down to know-how and the awareness of modern automation technology.