Saturday, March 5, 2011

PROFIBUS – Full of adventure

For some of you, when you hear the word “PROFIBUS” you might cringe because of the problems you may have faced in the past with this fieldbus. When I hear PROFIBUS, I hear adventure, a new challenge and a new solution.

I recently travelled to an African country known for its happy people and great chocolate. That’s right, you guessed it…Ghana! Situated on the north west of Africa along the Gulf of Guinea, it’s a tropical forest teaming with gigantic pot holes (at least the route that I travelled was!).

Map of Ghana

Ghana travel route

The next morning,after 20 hours of travel and 4 hours of sleep, I was on my way to try and solve the elusive problem that was plaguing this plant. The problem was described to me as “three devices keep stopping and then we have to manually restart them”. After looking at the voltage levels, signal waveforms, message trace, statistics, etc on my trusty PROCENTEC ProfiTrace my conclusion was that the messages are getting corrupted by noise. Unfortunately there is not too much that can be done in terms of a permanent plant fix when the plant can't be stopped for a reasonable amount of time due to production pressures but the short term solution was to reduce the network speed and increase the retry limit to 3 (which was currently 1) to mitigate the damage. The retry limit is simply the amount of times the master will resend the same message to the same slave before it will flag that device as “not configured” and move on to the next slave. When this limit is exceeded the SCADA will report something like “lost communications to the device” because the device is not in data exchange anymore and often this results in the undesired “plant trip”.

The correct solution will be to rewire the network, keeping the PROFIBUS cable away from the high voltage cables. Where that is not possible they will have to run the cables in an earthed steel conduit. One of the problems they are facing is corrupted messages and since the network is laid out in a line topology, every message that passes that noisy area gets affected. A better solution is to create a star topology using a multi-channel repeater such as the PROCENTEC Profihub. This will reduce the amount of messages getting affected and allow the technicians to isolate which segment is causing problems.

IDX Profibus Profihub

The good news is I left the plant in a “better” running state and post their successful training (yes they all past the installer and engineers course – despite the trainer) with better knowledge on what and what not to do with PROFIBUS..

Where to next? I wouldn’t want to hazard a guess but I know I’m game for anything (even Antarctica)

And I know Jono is off to Abu Dhabi tomorrow to audit an Oil Rig, a first for our PCC!

Tuesday, March 1, 2011

Need for Tag Synchronisation and Management

Modern plant systems consist of various real-time data systems, often from different vendors and the data contained in these systems is usually not directly exchangeable. The requirement to share information between these systems has become easier to achieve over recent years due to the advent of standardized data exchange protocols and systems, such as those defined by OPC, or using products such as IDX Data Exchange Server. However, while sharing this real time data has become simpler, the management of the systems producing and consuming this data has not. Currently, if the real time data elements, referred to as tags, are added or removed from the data producers, manual intervention is required to ensure those tags are added and removed from all the consuming systems in order to ensure configuration synchronization between all systems.

Manual synchronization is a tedious process when the systems involved are large, changes are frequent, and where small changes, such as a change in a tag’s maximum value attribute, may go undetected. In the process world, this problem is often seen when plant data is logged into a data historian. In this case, it would be desirable that when changes are made to the source systems, such as the addition of data tags to the plant SCADA, for example, that these tags could automatically be setup and created in the data historian so as to ensure the historian tag configuration remains synchronised with that of the SCADA.

IDX Tag Manager is an advanced, intelligent software solution designed to solve this problem. The principal behind IDX Tag Manager is to simplify this synchronization and management process by:
  • Providing purpose-built system components that are able to talk directly to the source and target systems involved.
  • Detecting changes in configurations between source and target systems, and providing detailed information and/or summarised reports of those changes.
  • Allowing changes to be selectively applied to target systems.
  • Maintaining a history of any changes made in both the source and target systems.

Key benefits of IDX Tag Manager:

  • Reduced time & effort to maintain target system such as OSIsoft PI and Wonderware Data Historian.
  • Systematic, repeatable approach with greatly increased precision.
  • Provides a level of change control and auditability related to both Source (e.g. WinCC, Citect, Adroit, etc) and Target (e.g. OSIsoft PI, Wonderware Data Historian) Systems.
  • Responsive local technical support.
  • Free upgrades if on Software Support .
IDX Tag Manager contains components to communicate with commonly used systems such as Siemens WinCC, Microsoft SQL or custom format CSV files, while targets include Wonderware InSQL Historian, OSIsoft PI Historian, Microsoft SQL and custom format CSV files. Once configured, Tag Manager allows for the continued synchronisation of source and target systems with greatly reduced time and effort but with increased precision, control and auditability.

Please contact us for further information or for a demonstration of the benefits that IDX Tag Manager can provide to your business.