Maintenance diagnostics get a makeover

A chemical plant installed an online monitoring system on its cogeneration plant’s gas turbines to analyze vibrations and warn about imbalances, wear or other dangerous conditions. Soon the monitors began to sense problems. The maintenance crew could not determine the source, even after spending an entire planned outage trying to isolate the problem.

Finally, the plant called in Richard Pratt, a regional services supervisor for Emerson Process Management’s Machinery Health Business, Austin, Texas. From the start, Pratt sensed it was not really a vibration problem. “I saw a 60-hertz signal on all eight proximity probes and the four accelerometers,” he recalls. “Those signals were everywhere, even areas where I didn’t expect to see vibration.”

Pratt attached his portable vibration-analysis system to the turbine to check the accuracy of the online monitors. They showed only normal readings. “After that, I knew it had to be electrical,” he says. He quickly traced the problem to a ground loop in the sensors.

Pratt’s recollection underscores why a growing number of chemical plants outsource diagnostic maintenance. Pratt or someone like him is available when they have a problem. He has the right technical training. He brings specialized tools. Most importantly, though, he’s experienced. In the case of the turbine, he quickly zeroed in on the unusual 60-hertz signal.

“One of the biggest problems in vibration analysis is that many companies don’t have the resources to retain a full-time analyst,” Pratt explains. “That means somebody is doing the job in their spare time. Like any other skill, you have to have a lot of training and use it constantly to get good at it.”

Staffing shortfalls
Experience is critical in diagnostics in general, notes Ricky Smith of reliability-improvement-specialist Ivara Corp., Burlington, Ont. “You almost always have to outsource large, complex problems. You need somebody with experience, and you can’t get it unless you deal with major problems all the time. You can hire smart people, but can’t keep them in practice.”

That ties in with a wider problem at plants. After decades of winnowing down maintenance staffs, chemical producers have fewer trained workers. As members of this aging workforce leave, their skills become harder to replace.

“Diagnostics is not the most difficult thing to learn,” says Emerson product marketing manager Todd Reeves, “but every plant has turnover. People are promoted, recruited or they get good enough at data collection and analysis to start their own company. So you have to retrain people from scratch.”

In contrast, outsourced experts have both training and experience. “Most of the big, reputable firms meet all ASNT [American Society of Nondestructive Testing] certification requirements,” says Jim Humphries, vice president of performance technology for Fluor Global Services, Greenville, S.C.

The ability to respond rapidly to emergencies is also important. That’s why  gamma-scanner Quest TruTec, La Porte, Texas, operates seven offices in the U.S. “Mostly, we respond to emergencies,” says Dave Ferguson, director of tracer applications. “At least 50% of the time, they want service this week. About 25% want it tomorrow and about 10% want it today.”

These factors certainly have not been lost on chemical producers and are key reasons why diagnostic maintenance has long been outsourced. In the past, the work largely went to individuals or small consulting firms with narrow areas of expertise — one might monitor for vibration, while another provides eddy-current inspection.

Bigger benefits
Plants still use these small specialists. Now, however, larger firms like Emerson, Fluor and SKF are playing a bigger role.

Larger vendors typically have a lot to offer. They have the heft to sign multi-plant contracts. They conscientiously train and certify service personnel. Most can draw on deep analytical capabilities. Increasingly, they can deliver online products that monitor critical equipment in real time.

These bigger companies often provide maintenance diagnostics as part of a broader package. Emerson, for example, sees machinery health monitoring as one component of its PlantWeb services, which help companies optimize assets and implement predictive (as opposed to time-based) maintenance.

“Not only can we do their outsourced condition-based operations and maintenance management, but we also rewrite their work practices to take advantage of today’s advanced diagnostic technologies,” notes Reeves.

At Fluor Global Services, which will earn about $1.5 billion in revenues this year, outsourced diagnostics supplement the company’s broader plant maintenance and operational services, says Humphries.

“We help our customers figure out the right things to monitor and whether to monitor them full-time or periodically,” Humphries states. “We determine the right techniques to apply and what plant services they need to outsource. We help build their business cases, train people — we do it all, from soup to nuts.”

SKF, a company best known for bearings rather than the rotating equipment they go into, also is actively involved. “In the mid-1990s, we… started going into factories to do predictive maintenance as opposed to waiting until equipment came back for repair,” explains Scott Brady, director of product marketing for SKF Condition Monitoring Inc., San Diego. “Like everybody else, we’re selling equipment and services. “We do an audit, look at all the equipment and provide vibration analysis, temperature, process data inspection — all the things you need to achieve operator-driven reliability.”

Better tools
New technologies have made the migration to outsourced diagnostics easier. Nowhere is this more apparent than in data loggers now available. Many of today’s experts cut their teeth copying readings from portable instruments and re-entering them into spreadsheets to make calculations. Now, portable equipment not only captures information, but processes, graphs, analyzes and transmits it on the spot. “It was almost a black art when I began,” says Humphries. “In some ways, it still is, but the tools provide a lot of analytical help.”

A more-subtle change has been the application of statistical techniques to sampling. “We used to see RFQs [requests for quote] that called for us to test every third elbow and every six feet along a pipe,” Humphries recalls. “If you take samples from those same spots, though, all you know is what’s going on in those spots.

“Then, several companies developed techniques to take statistically valid random samples. That lets you evaluate a system far more thoroughly and with less sampling,” he says.

Recently, online analysis has begun to catch on. Today’s highly networked plants make it easier to collect and share data from permanent sensors and analytical devices attached to equipment. Like all electronics, these tools have grown in capability while falling in price.

Emerson’s CSI 4500 Machinery Health Monitor, for example, continuously monitors turbines, generators, compressors, pumps and such large machinery as paper machines. “It automates the collection and review of vibration data,” says Reeves. “It can adjust the alarm process based on machine speed or operating condition and go to an alarm condition when vibrations exceed what’s expected.”

Emerson’s new, lower-cost CSI 9210 Machinery Health Transmitter specifically targets motor/centrifugal-pump combinations and features built-in intelligence for analyzing motor/pump problems. Reeves estimates that it would cost $6,000 to $7,000, including installation and some configuration, to monitor a pump with a CSI 9210.

At those prices, online data collection does not compete economically with a technician and a data logger. “The key is to pick the best business case,” says Humphries. “If you have a critical piece of equipment running at a zillion rpm, it can crater pretty quickly. You don’t want to test it just once every month. What we usually find is that plants need a mix of real-time diagnostics for critical equipment and periodic monitoring for less critical assets.”

Wider value
Online monitoring offers advantages that go beyond maintenance alone. It enables companies to operate their plants in very different ways, says Lars Jorgensen, district general manager of corrosion-monitoring-specialist InterCorr International, Inc., Houston, which was recently acquired by Honeywell Process Solutions. Its SmartCET system collects and analyzes 13 variables from permanent corrosion sensors to provide up-to-the-second information on pitting and general corrosion.

“In the past, people would adjust corrosion inhibitors based on historical data,” says Jorgensen. “Now they get immediate feedback on whether they’re pushing their plant too hard. They can decide immediately whether they want to live with the corrosion or increase the amount of inhibitors.”

SmartCET’s online capabilities naturally fit with Honeywell’s Experion Process Knowledge System (PKS), which also has a service component. “We’re still discussing business strategy, but we see a lot of services we can offer our customers through Honeywell,” Jorgensen observes.

In the pipeline
Online monitoring receives a lot of attention, but conventional outsourced services continue to proliferate. For example, Quest TruTec,  best known for scanning distillation columns with gamma radiation to assess their hydraulic performance, now has branched into infrared, ultrasonic, eddy-current, vibration and real-time radiography monitoring services.

Its offerings continue to expand, says Ferguson. The company’s new Furnace Tube Inspection System (FTIS) flushes what Ferguson calls “an intelligent pig” through a furnace’s radiant and convection tubing to ultrasonically measure tube anomalies.

“Customers want it because those tubes are too tightly packed to measure easily,” he says. “If these tubes fail in the middle of a run, they release process gas into the hot box. If you do a search, you’ll find several units that have burned down this way over the past few years.”

The company’s Laser-Optic Tubing Inspection Service (LOTIS) is also new. It uses lasers to map ovality, corrosion and creep within reformer and furnace pipes.

In contrast, Everest VIT, Inc., which was recently acquired by General Electric Corp.’s Inspection Technology unit, Lewistown, Pa., uses cameras, some as small as 3.9-mm diameter, attached to guide tubes or mounted on robotic crawlers, for visual inspections of pipes and tanks. “It lets companies avoid disassembly or [the need to] enter dangerous confined spaces,” says inspection services manager Jim Adams.

“The camera is the smallest part of it,” adds Adams. “People call us because our operators have learned how to maneuver cameras down long pipes. Doing that and getting meaningful images have a lot to do with the creativity of the technician. Our guys can also help them interpret the video, since they’re experts in looking at things in awkward positions or less than optimal lighting.”

An ongoing debate
While many companies outsource at least some diagnostic maintenance, some experts, such as Ivara’s Smith, caution that plants must understand both the pros and cons.

“On the pro side,” he says, “outsourcing diagnostic services enables plants to do more predictive and preventive maintenance. They’re usually working with good people who went to school, spent money on training, and know what [needs] doing.

“On the con side,” continues Smith, “companies outsource because they know they need help but don’t want to spend the money. That means contractors have to bid low to win contracts, so they’re looking to cut corners any way they can. They may not collect all the data they really need. Sometimes, instead of backing away from a deal they can’t do right, they take the contract anyway.”

R. Keith Mobley of Life Cycle Engineering, Charleston, S.C., who does predictive maintenance training, stresses that data have little value unless they are used to find the root cause of equipment failure.
He recalls a large steel mill that outsourced vibration monitoring. “Before outsourcing, they spent $2.4 million annually on bearings alone. In the sixth year of the contract, that had risen to $14.7 million.” 

Mobley led a program to discover why the bearings failed. More than a quarter of the failures stemmed from “penny wise” bearings purchases. However, two-fifths of the failures occurred because maintenance crews did not know how to install the bearings or had incorrectly applied or used the wrong lubricants.

Mobley believes many plants would do better by keeping diagnostic maintenance in-house. “You get better ownership and continuity because the guy who fixes your problem today is the same one who was there yesterday.”

Yet he is willing to outsource with a single condition: “Are your vendors willing to guarantee that they will correctly identify the root cause, provide the best corrective action, and sign their name on the report?”
Not bad advice for anyone shopping for outsourced diagnostic maintenance.