How to keep a factory running beyond using PLC diagnostic tools

Programmable logic controllers (PLCs) run millions of processes and machines inside factories. PLCs have a lot of processing power and handle a variety of inputs or outputs. They typically run protocols like Profinet, Profibus and, to a lesser extent, CANbus.

Depending on the factory, plant personnel have created tactics over time to get production lines up and running as fast as they can when there’s an unexpected interruption. But these tactics typically struggle to pinpoint problems, precisely analyze issues and reduce downtime.

When it comes to automation protocols, most have built-in diagnostics. So, if something goes wrong with a machine, the PLC gets a message. That’s fine if the problem is at the level of a component. But, in general, downtime in manufacturing means a whole process (such as sorting packages) grinds to a halt. In those cases, either a protocol’s built-in diagnostics don’t adequately convey the problem, or the diagnosis is just a symptom of another problem.

许多Ethernet-base首选诊断的解决方案d protocols would be running Wireshark, an open-source network protocol analyzer, that grabs and shows data traveling back and forth on a network. With the Wireshark trace, a plant technician would tap into the plant’s protocol via a switch to catch all the message traffic, while mirroring it on, say, his laptop to see what might be wrong on the network. But Wireshark is catching SNMP traffic and all kinds of other packets.

Industrial technologies to quickly pinpoint what’s wrong

If a technician isn’t well schooled with the use of Wireshark, there are other diagnostic and monitoring technologies. These technologies sit permanently on an industrial Ethernet factory network to record the traffic around a particular event and download the data to a web browser. From there, a technician can use Wireshark to run a trace. Diagnostic and monitoring technologies like this allow network administrators, engineers and operators to monitor complex systems and quickly see from a remote location when trouble is brewing to prevent unexpected, expensive downtime.

Industrial network fault monitoring, detection

With a diagnostic technology that is permanently installed to monitor industrial networks, or an advanced monitoring kit, factory managers can get a laser-beam focus on where trouble lies. These technologies can detect faults and diagnose problems on a higher level. Frequently, a process shuts down because a worker inadvertently jars loose a cable or disturbs a shield during, for example, routine maintenance. Advanced monitoring tools can spot an issue with firmware, cabling or a misconfiguration in seconds.

Using an advanced monitoring kit, which sits atop a plant’s network, maintenance managers can identify issues with, say, the Profibus stack or elsewhere. Several monitoring kits on the market these days have a built-in oscilloscope, so technicians can determine if voltages are at the proper level. Some industrial diagnostic technologies, which analyze fieldbus networks, work with specific protocols such as Profibus.

Industrial network analyzers with graphing capabilities

A monitoring kit permanently linked to a factory’s network means a technician can open a web browser and troubleshoot an outage. When evaluating tools to buy, technicians should consider analyzers that feature a bus monitor and graphing capabilities to quickly zero-in on trouble like configurations, protocols or cabling. If a factory runs Ethernet-based protocols such asProfinet,EtherNet/IPor Modbus TCP/IP, maintenance teams can tap handheld diagnostic tools and pair these with an industrial diagnostic kit like the ones mentioned above.

Often, the outages that drive control engineers and maintenance managers to the brink are interrupted processes that occur intermittently. These faults are hard to catch if a manager isn’t on guard with a tool; otherwise, the odds are slim of catching what’s causing intermittent faults.

Always-on industrial network monitoring tools can find intermittent problems

With always-on monitoring tools and kits residing on a system, a plant manager can gain a sense of what’s going wrong as it happens (such as when a connector that loses contact off and on between copper and cable for seconds at a time). Eventually, most connections will fail. But a technician or maintenance manager armed with an advanced monitoring kit can catch scope images that quickly identify a problem like a failing connector. Alternatively, maintenance managers can routinely check their monitoring kit. Some have Microsoft Windows-based tools that roll up data into a color-coded screen (such as red-yellow-green alerts). When managers see a problem, they can click on the issue and drill down for data.

In some factories, like a pharmaceutical plant, an hour of unplanned downtime due to a line going offline could cause the disposal of hundreds of thousands of dollars in drugs. To minimize downtime, go beyond PLC diagnostic tools and, instead, opt for advanced monitoring kits and devices. With the latter, plant managers can not only troubleshoot and maintain their production lines but also regularly watch their technology and even predict when things may go awry.

Rick Rockershousenis vice president ofGrid Connect, provider of embedded and networking technologies. Edited by Mark T. Hoske, content manager,Control Engineering,CFE Media and Technology,mhoske@cfemedia.com.

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