Wireless transmission cuts condition monitoring costs

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.

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.”

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.

“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.”

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

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.”