Profibus health check

The evolution from the days of 4 to 20 mA output communications to intelligent Fieldbus analysers may mean more diagnostic data is transmitted, but in order to ensure the data is reliable a new type of engineer with Profibus certification is required. Not only is this training expensive, but the engineer must have capabilities across all slave devices such as instruments, motors and drives to effectively analyse the performance of the Profibus network and the speed of its communications between the instruments and the master, the Gateway operating system. Furthermore, purchasing test equipment is costly where many plants may have a limited budget.

ABB’s current knowledge and experience of instrumentation is well placed to bridge the gap between plant instrument engineers and system engineers, so that all plant or process measurement data is available.

As part of the service, a comprehensive report including a list of devices on the network, signal waveforms, recommendations and findings, will be generated to confirm the Profibus network’s current performance. Testing equipment is provided by ABB too, so that plants need not purchase it to be used once and left in storage.

One example of the benefits of this service can be found at Imperial College London’s carbon capture plant where ABB Service Engineer Paul Bick connected a Profibus analyser to the plant’s communication system. The results revealed that the optimum speed for performance was 1500kb/second rather than its previous speed of 500kb/second, and increasing the speed to the new limit immediately produced a significant increase in response time from the instruments.

The Profibus health check also includes a review of the installation method. The Profibus Installation Guideline document refers to maximum cable lengths and cable segregation. During his service at Imperial College Paul Bick established that the cables were too short. The university quickly removed the risk of issues with reflections, data corruptions and interferences, by following his advice to extend them.

As standard, service highlights also include rectifying faulty instruments so that both the network and instruments perform to specification.
It is recommended that a plant carries out a Profibus health check whenever issues have been experienced as the reliability and health of the communications network is fundamental to any plant’s performance.

Dave Head, service product manager for ABB Measurement & Analytics explains: "This service provides peace of mind by ensuring customers' Profibus networks are optimised for best performance. ABB's Profibus certified engineers fill the gap between the instrument engineers and system engineers which are currently lacking in most operations. This provides value to customers as ABB can offer support across the measurement network.”