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Smart devices make the difference when determining shutdown causes

Monday, July 17, 2017

A process shuts down unexpectedly. A plant technician is called to find and fix the problem. No one witnessed exactly what happened. The technician must therefore systematically inspect the equipment involved. He or she might restart the process, hoping to make it repeat the fault condition. However, numerous components are involved. Applying diagnostic tools to any one of them is time-consuming, and the technician typically can focus on only one process component at a time.

Today's Industrial Internet of Things (IIoT), including wireless smart devices, can help rectify the situation. The technologies involved do so by giving technicians quick access to the right information. They can quickly determine which equipment was not involved, reducing troubleshooting time. In addition, smart, connected devices deliver real-time information during a process restart. These valuable diagnostics were virtually unavailable or financially impractical on factory floors until recently.

What makes this an urgent topic is that maintenance budgets are under pressure even as population demographics indicate our most experienced and skilled technicians and engineers are near retirement or already retired. Those taking their places may know the latest software tools, but how good is their understanding when it comes to the best way to diagnose a failed or failing motor or pump?

In these circumstances, wireless and other IIoT technologies can deliver real support to troubleshooting efforts, matching emerging technologies with a new generation of technicians.

Purpose of convergence

It has been widely remarked that operations technology and information technology (IT) are converging. Tools being used on plant floors today reflect that. For traditional operations people—many of whom have been around for as many as 30 years-the primary tools are the voltmeter, ammeter and oscilloscope. These individuals have the skills and qualifications to enter a "live" panel and work in it safely.

Those from an IT background, on the other hand, have a modus operandi that tends more to plugging in an Ethernet cable and going back to the office, or using a smartphone, to view the relevant data. They're probably not very comfortable getting into live equipment, nor do they have the experience with the tools that the previous generations used regularly. Yet trends indicate that these are the people who will be handling maintenance duties in the future.

Although wireless monitoring is useful, it's most useful when integrated into an asset-management system. However, at the same time, tethering a smart device to the asset-management system can be a challenge, because locating data for a given component or sensor requires going to a dedicated terminal. For troubleshooting, it's better to have access to the asset-management data from the plant floor, without recourse to a dedicated workstation being necessary.

An example of a smart device that can prove very useful, if not tethered to the asset-management system workstation, is a motor-protection relay. A motor-protection relay monitors for multiple faults, including overloads, underloads, undercurrent, current imbalance, phase loss, phase reversal, overvoltage, undervoltage, voltage imbalance, rapid cycling/jog, contactor failure, zero-sequence ground fault and motor overtemperature. Most motor-protection relays have a networking connection that allows their use with Modbus, DeviceNet, Profibus, Ethernet or some other network standard.

Even short-range wireless connectivity allows a plant-floor technician access to all appropriate data, including the fault history, for example, from the motor-protection relay. Technicians also have access via a smartphone application to all associated information in the cloud, including manuals, datasheets and the like.

Data needs context

Like IIoT itself, "Big Data" is useful as a concept because it reflects the growing power of information technology in industrial-operations environments. As a term having a certain currency, it is part of the realization that a lot of the process data we already have in hand or which we can easily acquire will now cost-effectively be put to good use.

Data, however, is of little use to a factory-floor technician unless it's properly filtered and context provided. In today's world, a technician might spend hours or days sifting through normal readings to find anomalies. This wastes time and is a negative incentive for any technician who wants to be productive. The service person needs data pertaining to the exception, not the rule.

As an example, let's say in the past there was a power problem. To address the situation the first step was that someone from a utility company hooked a logging meter up to the power system. Once a minute, it printed out a set of voltages. The utility company left it logging for days. Eventually, a representative would say, "Well, everything looks good to us; here's a stack of paper that we just printed out; we didn't see anything wrong there."

All the stack of paper proves is there were many long hours of normal operation. The one or two bad readings in that paper stack that it would be useful to know of, may take some time to uncover.

Storing data in the cloud may be more convenient and promise better productivity, but digital records are often just as poorly utilized as that stack of paper. We should be very specific about what we store and not just store everything we can, even if we have the room to do it and it's not expensive. There must be a purpose behind all of it, and we must be able to use it quickly and easily, to our advantage. 

A closer look

To see the difference that IIoT and wireless can make, let's go back to our earlier example. A cooling pump quits. The operator calls the maintenance electrician and says, "I've had cooling pump number-two go down twice; I reset it and it went down again. You need to come down here and figure out what's wrong with this thing. We've stopped the process."

When the electrician walks up to this equipment, he or she really has no way of knowing what just happened. They only know the equipment tripped off, was reset, and tripped off again. It could be a power problem, blown fuse, damaged motor starter, bad motor or pump bearings, failed motor or any of a host of other potential problems.

The pump motor has some sort of electrical protection—either a simple overload or, if the electrician is lucky, a smart motor-protection relay. If the motor-protection relay is equipped with a remote display, or if the cabinet has a window that allows looking at the local display, there may be some indication of what went wrong. But few power panels have such windows and most motor-protection relays are installed without remote displays. A simple thermal-overload device has no display at all.

Lacking a remote display, the electrician gathers whatever diagnostic equipment might be needed—voltmeter, ammeter or other device. He gears up with the appropriate personal-protective equipment, depending on the arc-flash-hazard level indicated on the panel's arc-flash warning label. Finally, he throws the disconnect on the panel to "off" and opens the panel.

The electrician then re-energizes the open panel and resets the relay. If the motor-protection relay has a display, the electrician can push the reset button to bring up the code for the last fault. If the relay has a network port, it's also possible to plug in a laptop or tablet and get the same information.

The electrician restarts the motor, which runs for a couple of seconds and trips right back off. He connects a single-phase ammeter to the first phase and tries to restart. Finding the current normal, the electrician goes to the next phase, and continues until finding a phase in which the current is not normal. He inspects the wiring and finds a conductor that's bad. He's solved the puzzle, but it has all taken a fair amount of time. 

The difference IIoT makes

What would happen in the same situation, if the motor-protection relay were a smart unit connected wirelessly? The electrician walks up to the panel but does not de-energize it or open it. Instead he pulls out a smartphone, bring up an application and connects the smartphone via Bluetooth to the pump's motor-protection relay. The fault history indicates the device has tripped twice recently on what is considered a contact failure.

The electrician reviews other related information and sees that during the fault one of the currents on a three-phase motor is at zero amps. Clicking on the information screen produces a "contact-failure" message, which means the voltages are normal but there's a single phase in the current. The potential causes listed include a faulty contactor, motor starter or motor wiring.

At that point, the electrician turns off the panel disconnect. It's unnecessary to put on any protective equipment because the electrician won't be working on a live panel. A quick inspection inside the panel doesn't show anything obviously wrong, so the next step is to check the pump-motor wiring. Opening the junction box shows one of the motor terminations is discolored, indicating damage from heat. After repairing the bad terminal, the electrician closes the junction box and re-energizes the panel. Everything works properly and the problem is solved.

The motor-protection relay prevented damage to the motor. Use of diagnostic equipment or work in a live environment wasn't required. The electrician found the solution to the problem quickly without any tools other than the smartphone in his pocket and perhaps using a screwdriver to open the terminal box.

An intelligent motor-protection relay with a Bluetooth connection to a smartphone eliminated most of the work and time required to solve the problem. It was unnecessary to look at the fuses because the fault record showed they weren't a problem. Nor was there indication of an overload, such as from bad bearings or something wrong in the motor's operation. The electrician didn't have to inspect the motor or pump for mechanical problems. The power system wasn't to blame, so it wasn't necessary to haul out the voltmeter and test the power system.

Three of five possible problems were eliminated by having direct access to plant-floor fault information. The key was getting to it quickly. And best of all, there was no need to haul out the manual for the relay because that information was readily accessible via a smartphone application that brought up the appropriate section of the user manual, including the fault description and its possible causes.

Bluetooth beats Wi-Fi on plant floors

Kip Larson, a director of product technology at Littelfuse, says Wi-Fi, the most-frequent choice for wireless Internet access, is not as good a choice for plant-floor diagnostics as Bluetooth.

To start, Larson said, "It has too wide a range, posing security concerns. A single Wi-Fi hotspot can have a range up to several hundred feet. Bluetooth has a shorter range. The smart overload relay used as an example in the article uses Bluetooth 4.0. Bluetooth Low Energy (aka BLE or Bluetooth Smart) Class 2, should have a range of about 20 meters in open air, and five to 10 meters when mounted inside a closed metal cabinet. This allows the electrician or technician to communicate with the relay while standing next to the motor, but it stymies more distant intruders. In addition, the relay and the smartphone application that goes with it require a one-to-one pairing code, plus password security, for changes. 

Final words

IIoT devices show great promise for plant maintenance but efforts are limited if connection are via Ethernet or other wired networks, or if less-than-secure wireless systems, are needed. Use of a short-range wireless technology such as Bluetooth, combined with data storage in the cloud, greatly simplifies electrical maintenance. It also fits in well with the way the next generation of technicians approach their work.

Kip Larson is director of product technology, electrical business unit, protection relays, Littelfuse, Inc. He has more than 30 years of industrial electronics product design and application experience. He received a B.S. in electrical engineering from South Dakota School of Mines and Technology.

Callouts:

Wireless and other IIoT technologies can deliver real support to troubleshooting efforts, matching emerging technologies with a new generation of technicians.

Like IIoT itself, "Big Data" is useful as a concept because it reflects the growing power of information technology in industrial operations environments.

This article appears in the IIoT for Engineers supplement for Control Engineering 
and Plant Engineering

- See other articles from the supplement below.

View the original article and related content on Control Engineering