1660328967661 Article Wireless1

Wireless transmission cuts condition monitoring costs

July 9, 2009
Wireless condition monitoring cuts the cord on productivity.

Industrial facilities are under increasing pressure to improve reliability while cutting the cost of maintenance manpower and materials. Studies show that leading facilities spend less, yet have higher scores on critical key performance indicators such as overall equipment effectiveness (OEE), mean time between failures (MTBF) and maintenance cost as a percent of production.

We know the key to spending less and getting more is to do the right thing at the right time, a nice way of saying, “only what’s needed, at the last minute.” But what, exactly, is needed? And how much time do we have? The science of condition monitoring (CM) was developed to answer those questions.

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But CM technologies such as oil analysis, ultrasound, thermal imagery and vibration require their own investments in installation and labor. Where it’s appropriate, wireless data transmission empowers condition monitoring by reducing those costs. This increases paybacks and allows facilities to apply more effective condition monitoring to more equipment.

Keeping a better eye on assets can mean the difference between success and failure. “On a global scale, in North America we have some of the world’s oldest facilities competing with brand new plants in China,” says Bob Karschnia, vice president, wireless, Emerson Process Management (www.emersonprocess.com). “Products can be sourced all over the world. Older plants need to monitor and control their processes better, and they can do this with wireless.”

The Holy Grail

Wireless might be an option for any condition-monitoring technology that must transmit data, but most of our experts used vibration monitoring as their example. Vibration has traditionally been split into high-end protection systems used only for expensive, critical machinery like turbines, and portable equipment for route-based monitoring.

“Critical machinery gets $100,000 protection systems,” says Bart Winters, reliability solutions manager, Honeywell (www.theoptimizedplant.com). “Less critical machines might get $20,000 wired systems, and everything else is manually probed at intervals, typically weekly or monthly. That costs $600 to $11,000 per year, depending on its location and how often it’s done, and it’s not frequent enough to always protect the equipment.”

Machine TV

It’s now practical to add video to condition monitoring and control networks. When sensors indicate something needs attention, a video system can send a short clip attached to an alarm message, showing what happened before, during and after the alarm. This message can be sent directly to a cell phone so that a technician has an instant view and understanding of what needs to be done. The system can link the stored video with messages or other database information (such as condition measurements, trends or even scheduled maintenance data) so that those data have a visual context for better understanding, and the operator can examine the situation from the control room, using pan-tilt-zoom camera features to take a closer look.

“The trick is how to handle all the video that’s being generated before, during and after any monitoring event,” says Steve Rubin, president and CEO, Longwatch (www.longwatch.com). “That’s why it’s important to have local recording of the video on the plant floor.” Systems like Longwatch provide the support needed to handle the high volumes of data generated by video systems using low-bandwidth plant floor networks.

A video on the company’s Web site shows an oil leak at a power plant. The operator is able to see the leak long before the leak sensors on the floor trigger in the control room. The operator can stop the pumps, avoid large environmental fines and document scope and clean-up for the EPA. “This has saved the customer a lot of time and money and oil,” Rubin says.

Video is on the rise. “The cost per pixel is dropping like a stone, with motion control-quality cameras moving from $25,000 to $5,000,” says Hesh Kagan, managing consultant, Invensys Process Systems (www.ips.invensys.com). Intelligent recognition software can detect interesting motion and focus in. “It opens the possibility of telepresence: I can get data from anywhere to anywhere, why not myself?”

We would like to take measurements on more equipment, more often, but, “Wired systems cost too much to install — typically 10 times the transmitter cost to put one in,” says Todd Reeves, product manager, machinery health management, Emerson Process Management. “It becomes a big capital project that’s hard to justify. Maintenance guys fight the emotional battle and the economic battle, but it’s too hard so they just use routes and hope things don’t break between rounds.”

So, what the people need is a lower-cost, lower-labor approach, says Mark McGinn, managing director, SKF Condition Monitoring (www.skf.com). “The holy grail is a wireless system that competes with both portable and traditional wired systems by reducing the manpower costs of route-based monitoring, and the equipment and installation costs of traditional online systems.”

Define “wireless”

When you say wireless, most people think of wireless sensors. These are becoming commonly available for simple process variables such as temperature, but have cost and battery life issues when used for complex data collection. “There are a few out there, but low power equals low bandwidth, which is a problem with vibration,” says Jonathan Hakim, president, Azima DLI (www.azimadli.com). “You can get overall vibration levels and scalar values, but not spectra.”

Other experts say the cost of a reliable, capable sensor is still too high. “If a route-based system costs $125 per point, it’s hard to justify a wireless transducer,” says Tom Millis, manager, global reliability services, Timken (www.timken.com). “The application for a $100 sensor has to be simple and steady-state, like some pumps.”

The time will come. “Two years ago I said the killer app was going to be the low-cost, ubiquitous, wireless condition-monitoring sensor to monitor behavior with model-based predictive systems. Life would be good,” says Hesh Kagan, managing consultant, Invensys Process Systems (www.ips.invensys.com). “But the low-cost condition-monitoring sensor hasn’t occurred. So give it another two years.”

Meanwhile, we’re left with two viable configurations: battery-powered, wireless sensors that transmit limited information and alarms (see sidebar, “A paper case”), and conventional sensors wired to a device near the machine that transmits wirelessly around the facility. The latter offers the opportunity to gather data more often and more accurately than route-based monitoring, as well as access to equipment in remote or unsafe locations.

The walkaround without the walking

Wireless can connect wired systems into a wireless network so you can do the walkaround without the walking. “Assets that did not justify wired systems but have a history of failures that affect production and happen between walkarounds offer an ROI on closer monitoring,” says McGinn. “Wireless has a lower installation cost that can let you address pumps, fans and gearboxes in this category.”

Cost savings are relatively easy to calculate for wireless transmission as opposed to route-based monitoring. “There’s a whole class of important equipment, like blowers and agitators, that’s not critical enough to justify a continuous monitoring system but needs more than manual probes. On those, you can use a wireless system to get a daily sample as opposed to weekly or monthly.

A wireless manifesto

Nigel Leigh, chief product architect, Commtest (www.commtest.com), says users should demand these characteristics to have a truly useful wireless condition monitoring system:

  • A robust network for secure and reliable transmission in industrial environments.
  • Easy installation, both physically and by integration into a single system for walkaround, continuous wired and battery-powered wireless systems, with data visible in the same system.
  • Low maintenance, including robust sensors with long battery life and easy battery replacement.
  • Appropriate reading frequency: Once a day or week is enough to do accurate predictive maintenance, but leave enough circuitry powered all the time to detect when a change in average vibration exceeds a preset value, then wake up and warn that the level is exceeded.
  • Physical size: A big antenna poking out is not a good thing. A sensor should be low-profile, light enough for good coupling to the machine, simple and easy to manufacture.
  • Data quality: Many sensors only return overall energy, spike, peak or overall demodulation and it is not enough to diagnose the fault. You need a full-spectrum output.
  • Value: The best benefit to cost ratio, with multiple axes, temperature and wake-on-high-vibe capabilities.

“The cost is much lower than $20,000 or even $11,000, and you get a full vibration spectrum for analysis, not just overall vibration,” says Winters. “You can detect the nature of the problem — bearings versus balance, etc.”

Honeywell piloted a wireless system on pumps in a BP oil tanker, and is deploying it on centrifugal compressors, pumps, agitators, fans and blowers at its special materials facility in Hopewell, Va. To understand the value proposition, they looked at the unplanned downtime during the past three years and estimated the maintenance cost and the data collection cost of walkaround versus wireless. “The savings is mainly in downtime due to visibility and planning,” Winters says. “We also save by reducing emergency work and on secondary damage. For example, material builds up on a fan and we can see the out-of-balance situation and correct it before it damages the fan or bearings. We also save on monitoring labor.”

A typical Hopewell estimate is shown in Table 1. “When we calculated what was actually being spent with the walkaround system, the real maintenance and loss numbers were four to 10 times higher,” says Winters.

Wireless offers the greatest benefits in equipment that is remote, inaccessible or dangerous. For example, OSHA regulations and company policies don’t allow people on the cranes anymore. Instead of using a handheld, you can monitor them with wireless.

Technicians doing routes on cooling towers might have to climb 40 ft. to the motor and gearbox to measure vibration. This is dangerous, especially in the winter because of ice. “You could mount sensors and run wires to a box at ground level, but with wireless, you don’t have to do that and deal with the manpower and scaffolding,” says Reeves. “We are able to implement a cooling tower motor and gearbox in half a day at a tenth of the expense, and you don’t have to go out and measure it at the junction box.”

  Route-based Wireless
Labor Collect data monthly $600, weekly $2,600 Labor and analysis $780
Maintenance (70% labor, 30% parts) $15,000 $9,900
Production loss $10,000 $5,000
Total $25,600 to $27,600 $16,700

Streamlining route-based monitoring with wireless also can be a way to continue (and improve) predictive maintenance programs despite today’s pressures to cut costs. “These days, sites are resource-limited and diverting vibration labor to other activities,” says Winters. It won’t be long before they’re spending more on breakdowns. “They’re trading operating labor for capital expense,” he says. At Hopewell, monitoring labor was being diverted to non-rotating equipment like piping and vessels, to take ultrasonic readings. “We were going to be in trouble on vibration, but this solved it,” Winters adds.

With wireless, condition information is in real time. A mechanic can acquire the machine ID, download its information and verify that he’s working on the right asset. “Getting the right information while the mechanic is on-site saves paperwork headaches,” says Robert Landsfield, CEO, Skymira (www.skymira.com). When a mechanic uses a part, it gets billed out instead of forgotten, which can reduce parts losses. “And a system can help gather information on how mechanics move through the day, to help improve ROI on the human side,” Landsfield adds.

Fit for retrofit

Deathwatch

A favorite use of wireless is for temporary deployment of vibration monitoring on faltering machines to move from monthly to daily monitoring . One engineer leaves a portable wireless system in a cabinet in the control room. If an off-shift operator notices a noise or problem and calls in the night, he has the operator get it out, put the magnetic-base sensors in the marked spots and turn it on. In 20 minutes he downloads the diagnostics over the Web from his home.

The approach requires no drilling and tapping, conduit, wiring or shutdown. You can instrument a problem machine, solve the problem and move on to the next machine. If you’re doing rounds and find a piece of equipment that’s rough, but you need to run it another month before you can shut it down, you can put on a wireless portable unit to babysit it.

The cost savings and flexibility of wireless versus wired installations makes them especially viable for retrofitting existing equipment. “Along with the 80% or 90% cost savings, there’s also a significant time savings,” says Joseph Citrano, wireless program manager, asset optimization, Emerson Process Management. “Wireless can be done in a week or 10 days from order to install. Project time and complexity is much less, and so is the cost. Instead of $20,000 or $30,000, it’s an amount that fits into a maintenance budget.”

You can add wireless instrumentation to old equipment. For example, new compressors have instruments to verify lubrication. Old ones don’t, so you can add lube oil monitoring system flowmeters and pressure gauges. There are wireless gauge readers that attach to conventional dial gauges and transmit their readings.

“The big driver is cabling costs,” says Nigel Leigh, chief product architect, Commtest (www.commtest.com). “Sensors cost less than $100 but labor makes wire and conduit costs much higher.” For example, Leigh uses wireless to monitor aeration pumps in the middle of settling ponds. “How would you get the sensor cables out there?” he says, admitting that wireless is not ideal because “batteries go flat.”

Others say the battery issue has been largely laid to rest, with battery life on vibration sensors now up to five to eight years (exceeding 10 years for pressure and temperature transmitters). “The batteries are trended and alarmed,” says Reeves, “so you know when the power module is getting low weeks before you need to replace it.”

Other commonly cited issues such as electrical noise and security have also been largely resolved with lessons learned on difficult applications such as battleships and chemical plants. “The nuclear industry put us through the paces,” says Hakim, and commercial technology is doing the job “surprisingly well.”

Bluetooth is good for gathering data from machines with hand-held devices — you just hold them nearby to get data with date and time stamps. And wide-area cellular, satellite or microwave networks work in areas where there is no Internet access. Pipelines and remote pumping or compressor stations can send full-spectrum data at intervals.

“An oil and gas company with many compressors approached us with a paperwork problem. They needed to scale up the business and deploy more compressors, and they already were processing 4,000 work orders a month. The work orders came in from all over by Fed Ex, fax and carrier pigeon, and they couldn’t keep them straight,” says Landsfield. “They shifted from paper-based to an interactive, computer-based system that let them monitor the compressors, know when they’re down, trend them and do predictive maintenance.”

Figure 1. Information from both the equipment and the mechanic can be combined to tell field technicians which remote equipment needs work and what work is needed, not just to inspect it. Source: Skymira.

Information from both the equipment and the mechanic is transmitted as satellite packet data over a variety of platforms, brought together and presented in a common display. Field technicians are told when a compressor needs work and what work is needed, not just to inspect it (Figure 1).

The cost of sending full-spectrum data over long distances is poised to fall as available bandwidths and transfer speeds from new satellites and protocols increase. “Now, all the terminals are low-data-rate and need a special protocol,” says Landsfield. “In the next 18 to 24 months, two or three new satellites will be launched that will be capable of IP-based terminals with much higher data rates, higher data collection frequencies and lower costs. It’s a disruptive technology with the potential to move the cost of a 5,000 or 10,000 terminal network from millions of dollars to less than $1 million.”

Bring in the data

Route-based data too often goes into the reliability department and never exits. When data is brought in automatically over the air or through a network, its value can be increased by combining it with time, date, location, process and asset information.

“Handhelds are pretty slick, with four-inch screens and Windows operating systems,” says Kagan. “Combine them with bar codes, RFID, voice or video, and you have lots of flexibility in how you address problems.”

A paper case

In late 2008, GHP installed the Timken StatusCheck system to monitor three boiler feedwater pumps and associated motors. The wireless system monitors bearing operating conditions and issues alerts via e-mail or text message when it senses excessive temperature or vibration.

“The feedwater pumps were chosen because they are extremely expensive due to their multi-stage design, high output pressure, lower tolerances and high historical maintenance costs,” says Bob Brennand, GHP mill manager. “If the pump fails and shuts down a boiler, the cost to the mill is approximately
$6,000 an hour.

“During the first four months of operation, the StatusCheck system has already notified our maintenance personnel of an imminent motor bearing failure,” adds Brannand. “Because of this, we were able to schedule a motor replacement. In the past, the bearing would likely have failed, leading to a higher repair cost and more downtime.”

As an interface between the equipment and bar code or RFID, you can ID what you’re seeing and get equipment information, safety warnings, red flags and lockout procedures. “Today it’s an identifier, but it can do more,” Kagan says. For example, data from remote locations can be acquired automatically during security rounds. “It can start up when you come into range, what we call a time-deferred network. As you drive by in the truck, the remote device dumps data into your handheld. Then when you drive back into primary network range, the data uploads into it.”

When condition information is brought in alongside process information, you know how the equipment was being run. “With wireless HART, we bring temperature, flow, vibration — process and condition information — into the historian,” says Reeves. “We can send it anywhere — the operator, the vibration analyst — and when there’s a problem, they’re all looking at the same data.”

If loads, pressures, speeds, etc. are not constant, process information can be essential. For example, loads on crane, shovel or dragline are dynamic. “The bearings might not even be making full rotations,” says Millis. “The system has to know when to take readings, with multiple types of sensors to know the load, etc. You have to measure what the crane is doing, and only compare data taken under equivalent conditions.”

Process information also can tell you if equipment is running outside its design limits. Winters says that more than half of maintenance costs are caused by misoperations like pump cavitation, dead-heading and running out-of-balance equipment. “A month of fan vibration because of product build-up means the fan goes down and we have a production loss,” he says. “When the operator knows, he can blow down or wash the fan. We get a real-time correction.”

Wireless can bring the cost of data integration down to where you can justify it with labor savings or improved reliability, then reap much greater benefits from “the convergence of machine condition monitoring and the mobile worker,” says Landsfield. Today, it takes several people to get data into the office and massage it to get value. “The goal is to have employees act in such a way that they can reduce the amount of work the equipment needs,” Landsfield says. “It all is coming in the same pipe — you have a wealth of information and can act on it.”

Some see wireless as the next competitive advantage, the new generation’s plant performance-enhancing piece. “Be creative, be imaginative,” says Reese. “People have consistently surprised us on their applications, partly because it’s the new generation that’s doing this. They’re less risk-averse, and less technology-averse.”

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