Food Engineering

Tech Update: Maintenance feels the vibe

March 26, 2003
For processors with the ability to exploit it, condition-based monitoring technology is delivering affordable tools that are easier to use.

Vibration analysis becomes more user-friendly and affordable with the MicroVibe analyzer, a device that links to a personal digital assistant. Source: SKF Reliability Systems.
POWER PLANTS AND PETROCHEMICAL PROCESSORS ARE THE ACKNOWLEDGED leaders in industrial maintenance. The sheer size and importance of those plants’ equipment make leading edge maintenance a mission-critical function.

Food and beverage processors, on the other hand, tend to trail the manufacturing pack when it comes to effective maintenance strategies. Decades of cost cutting that yielded short-term savings have produced programs that more closely resemble triage than predictive maintenance. Tools like infrared thermography and vibration analysis are regarded as too exotic or costly. The absence of solid fundamentals has more often than not produced disappointing results when companies have deployed computerized maintenance management software and enterprise asset management systems.

“There is a massive deficit in maintenance skills in food and beverage,” believes Robert Williamson, a maintenance consultant who numbers dairies, bakeries and ready-to-eat meat processors among his clients. “Food plants can benefit from condition monitoring tools by focusing on critical equipment first. However, if you don’t have a good preventive maintenance program in place, you’re not going to get the return on that technology because you don’t have the culture to leverage it.”

Even those plants that have instituted effective preventive maintenance programs often have been unable to use condition monitoring devices because of their cost. Happily, that is beginning to change, with the most dramatic changes occurring with vibration analysis, the cornerstone of condition monitoring.

The vibration signatures of imbalance, misalignment, bearing faults and gear mesh failures are distinct frequencies, and the amplitude of vibration reveals the severity of the problem. To take advantage of the technology, food plants either have had to contract with a service provider or spend six figures for the necessary equipment plus staff training to be able to interpret the collected data. With the recent introduction of the Entek XM series, lower cost, modular systems are becoming available to monitor and protect critical equipment.

“The majority of the technology is being applied at power plants and in petrochemical processing,” allows Richard L. Schlitz, vice president of capabilities and engineering with the Integrated Condition Monitoring Solutions division of Rockwell Automation. “As food and beverage plants look to improve their OEE (overall equipment effectiveness) scores, they’re taking a closer look at open distributed machine monitoring.”

Real-time condition monitoring in an easily configured system and at a relatively low price has arrived with the Entek XM series. The modular system interfaces with other Rockwell Automation asset-management systems and other open-architecture software. Source: Rockwell Entek.
OEE is determined by multiplying product of equipment availability by performance efficiency and rate of quality, expressed as a ratio. Downtime is the antithesis of availability, and both planned and unplanned downtime must be subtracted from the uptime ratio, Williamson points out. When a rigorous definition of equipment availability is applied, food-plant OEE scores tend to hover in the 50-55 percent range, Williamson and Schlitz agree. That’s not an efficiency score production managers are eager to report. Consequently, OEE often is misapplied or papered over, helping to perpetuate poor maintenance practices and their costs.

Because of its modular approach, Entek XM avoids the all-or-nothing predicament of existing vibration-analysis systems. Plants can initially target their most critical machines or the equipment most prone to failure and expand from there. Each module supports two sensors and can be configured to monitor vibration in rotating equipment, eddy current displacement, voltage output or a variety of process parameters. Simplified mounting hardware lets engineers place the modules close to the machine being monitored without a special enclosure or having to add them to existing control panels. Modules can be networked via an existing open network such as DeviceNet, reducing hardwiring costs and installation time.

Milford, Ohio-based Entek was acquired two years ago by Rockwell, and the relationship was critical in developing a lower cost monitoring solution, believes Schlitz, who has been with Entek for 20 years. “Would distributed, real-time monitoring have happened without the Rockwell acquisition? I don’t think so,” he says.

Expertise still is required to interpret and evaluate the measurements, whether they are collected in real time or periodically. However, the monitors can be set up to provide early-warning alarms to alert operators to developing problems. Maintenance can then take preventive steps while analysts bore deeper into the readings to determine the type of fault involved.

Some manufacturers are specifying maximum vibration frequencies for the new equipment they order, Schlitz says. Low vibration is indicative of a higher quality machine, and that means faster setup and fewer breakdowns during its service life.

Ultrasound technology has been used effectively to detect air leaks for decades, but the technology also is being applied to bearing inspections and electrical system faults. Source: UE Systems Inc.

Affordable portables

Continuous monitoring is where a system like XM really pays off. For plant operators who are more interested in capturing trend data, the threshold for entry into vibration analysis has been lowered considerably by SKF Reliability Systems, a San Diego instrumentation firm that recently began distributing the MicroVibe analyzer. The device plugs into the expansion slot of a Handspring Visor personal digital assistant (PDA). The analyzer costs $2,000, less if the user already has a Handspring PDA.

PDA-based measurement instruments are poised to change the cost equation of condition monitoring in food plants. IQ Scientific Instruments bases a pH meter it manufactures on Handspring, though the device is geared for QA personnel, not maintenance. “The market’s definitely moving toward PDAs, and the PDAs are becoming more rugged,” says Don Marshall, SKF’s product manager. “The beauty is that you have all the functionality of a PDA, plus you can plug in tons of software applications that can run on it.”

Lower-cost vibration pens are available, but they only take one reading. SKF’s next level of analyzers cost five times as much as MicroVibe, out of the reach of smaller plants with a few dozen pieces of rotating equipment. “I can show a person in two hours how to use this analyzer,” Marshall says. “You don’t need to be an engineer or a vibration technician.”

The device automatically tabulates five vibration measurements: acceleration, velocity, displacement, high frequency detection and enveloped acceleration. It helps users zero in on specific problems such as misalignment, imbalance or bearing faults. The unit can store more than 1,000 vibration signals and 2 megabytes of time waveform data. “It sends data in a comma delimited format for uploading to a database or spreadsheet to start building a history on a particular machine,” he says.

The size of a machine is no indication of how critical it is, says Marshall, dismissing the argument vibration analysis is only for huge generators and the like. “Before they started using our equipment, M&M/Mars had to throw away a day’s worth of production because a machine with a 10 HP motor that cut candy into pieces at the end of a line went down,” he recalls. “That was the value of condition-based monitoring to them that day.

“If there are three layers of redundancy and all you have to do when a machine breaks down is wheel in another one, condition-based monitoring isn’t important,” he concludes. “It comes down to, How critical is that machine?”

MIURA's Online Maintenance System provides trouble-shooting and diagnostic information.
Oil analysis is “probably the least costly condition analysis that plants can perform,” suggests Williamson. “The problem is acting on what the report tells you to do, particularly if you’re in a reactive maintenance environment.” For those more highly evolved along the preventive maintenance trail, a number of labs can provide useful feedback on not only the general health of the oil but moisture and particle contamination and wear debris and the likely root cause of the problem. They include Emerson Process Management/CSI in Knoxville, Tenn., Predict in Cleveland and Rockwell Entek.

Dow Corning is among the food-grade lubricant suppliers who offer oil analysis services (see story below), and the company has added a marker to its oil to measure age and condition, according to David Garner, the corporation’s leader of global lubricant-marketing strategies. “We’ve extended the time between oil changes 40, 80, 100 percent beyond the recommended interval with the test,” Garner says. Poorly executed oil changes are major contributors to premature wear, he maintains, so extending intervals saves more than labor and oil costs.

Ultrasound is another nonintrusive technology that short circuits the potential for maintenance-induced failure. It’s a relatively inexpensive and versatile technology that can monitor air leaks, steam traps and electrical arcing, even from a distance. “At an estimated cost of $7,000 per leak per year, air leaks are important,” points out Williamson. “There are plants that run two of their five compressors just to replace the air from all the leaks.”

Ultrasonic leak detectors have been around for 30 years, but the state of the art has advanced considerably. “Structure-borne problems such as bearing faults and cavitation problems can now be detected, notes Alan Bandes, vice president of UE Systems Inc. in Elmsford, N.Y. The ability to fine-tune the frequency received is a major advance. Digital devices are beginning to replace analogue units, which will usher in software applications that will make ultrasonic scanners more valuable.

“Ultrasonic scanners are the Rodney Dangerfield of predictive technology,” Bandes jokes, though a number of food companies are beginning to use them in their maintenance cost-avoidance programs, including Nabisco, Cargill and Coors. “People are using this in conjunction with infrared thermography because structure-borne ultrasonics give you the ability to listen through solid mass,” he says.

Overlubrication is a major cause of bearing failure. Ultrasonics can be used to establish a lubrication baseline to address the problem. Bandes cites the case of a customer who was re-lubing every other week; instead, six months proved to be the optimum interval.

Compared to vibration analysis, data interpretation is simple, though the handheld devices should be used by an expert in the equipment being evaluated. “A lot of the devices are intuitive,” says Bandes. “Within 15-20 minutes, you can start using them.” The ability to interpret signal amplitude and other feedbacks to determine the beginning of a failure mode requires a day or two of training. Five-day certification programs are available for technicians.

Built-in monitoring equipment is becoming common on major pieces of equipment, such as compressors and boilers. Not only is the cost of these add-ons coming down, the level of sophistication is increasing.

Miura Boiler Inc., the Wheeling, Ill., subsidiary of a Japanese boiler maker, recently introduced Miura Boiler Monitor (MBM), a customer troubleshooting tool similar to the supplier’s Miura Online Monitor (MOM). A PC with 512 megabytes of RAM drives the software diagnostics that scrutinize more than 100 data points from the boiler’s sensors.

As useful as MBM is, MOM is even better. A unique feature is MOM’s “sliding window,” which freezes four seconds of data prior to an alarm being triggered, according to vice president Mark Utzinger. “There are literally 50 different things that can cause flame failure in a boiler, and the precise reason can be identified in the data from those four seconds. It’s the electronic equivalent of a boiler operator staring at the flame for a year.”

Regardless of how far technology advances, the tools are of little value if a plant hasn’t developed the discipline to advance maintenance beyond the reactive mode. For those who have, technology to take their programs to the next level keeps getting better.

Besides reducing the frequency of lubrication, synthetic grease outperforms mineral-based lubricants and deprives bacteria of a possible growth medium. Source: Dow Corning’s Molykote Division.

Sidebar: Superior lubricants as a maintenance tactic

As many as 10,000 lubrication formulations exist to satisfy all but the most specialized industrial applications. That’s an argument for sticking with the tried and true, rather than sort through the overwhelming options. But food and beverage manufacturers are beginning to reassess the oils and greases they use, and ironically the impetus is coming from their focus on food safety.

“There’s a greater push toward total H1-certified food-grade lubrication programs,” explains Jim Gerard, general manager of Toledo, Ohio-based Lubriplate. Manufacturers are shifting from a commodity mindset, and that is giving suppliers the opportunity to discuss the merits of food-grade polyalphaolefins (PAOs), a category of synthetic lubricants that blend well with mineral oils and additives, says Gerard.

“Food especially is a growing market for PAO,” agrees David Garner, strategic leader-global for Dow Corning’s Molykote industrial lubrication brand. “It’s probably experiencing double-digit growth, depending on the region.

“Maintenance people are very skeptical about changing for change’s sake, and the food industry is an especially difficult market,” he adds. “They want to be able to extend their maintenance cycles, but they also want to be able to justify the higher cost of PAOs.”

Molykote synthetic oils cost four to five times as much as mineral oils for the same applications, but fewer oil changes can more than offset the differential. When labor savings and fluid disposal costs are factored in, synthetic gearbox oils and compressor oils can save a little or a lot.

Superior performance is where the real payoff comes, however. Oxidation accounts for the vast majority of oil breakdown and failure. About a third of mineral oils are elements other than hydrocarbon, and that’s where oxidation with water and other contaminants occurs. PAOs are almost pure hydrocarbon, according to Garner, leaving little opportunity for oxidation. Bearing wear begins when water particles reach the 500-750 parts per million range in an oil, he says; even after extended use, synthetics seldom exceed 160 ppm.