Predictive Maintenance and Condition-Based Monitoring

Reprinted with the permission of Equipment Manager magazine, the magazine of the Association of Equipment Management Professionals.

There are many, many definitions for condition-based monitoring (CBM),” says Diego Navarro, global fleet management solutions manager for John Deere Construction and Forestry Division. “Mine is being able to talk to machines to find out how they feel. [It] takes a set of tools to do this.”

The most important tool, perhaps, is oil analysis. Another one—if done correctly—is a vehicle inspection.

“An airline pilot always puts on his orange jacket and walks around the plane before flying. He looks at specific areas, checking for leaks, inspecting hoses and other critical components. He has an established walk-around routine,” Navarro says. “Afterward, he brings back his observations on what needs to be done and communicates them to maintenance.”

In the heavy equipment industry, that routine walk-around is just as important as that of an airline, especially since heavy machines work in dirt. “You will find physical wear that might not be so physical, on an airplane,” Navarro says. “In inspecting machines you look for issues such as leaks, a zerk that is not taking grease, low pressure tires, missing bolts or chafing hoses.”

Most fleet professionals know this, Navarro remarked, but the fact is many people either don’t know how to do it or do not have the means to do it. The problems crop up with how the results of the inspection are brought back to maintenance and administrative offices.

It is difficult, for example, when you depend on paper or electronic gadgets during inspections. “With paper, often it is hard to understand the technician’s scribbles,” he says. “With hand-held electronic devices, such as the hand-held tool used by Hertz to inspect airport buses and by some construction companies, you have to check the areas of inspection, mark them and scan all the sensors to make sure you’ve checked the whole machine, and then press ‘send’ to transfer the inspection data to the office where the data waits until someone acts on what needs to be scheduled.”

Ergonomically, it is difficult to walk around the machine with a computer or hand-held electronic device and, at the same time, inspect the machine, he says.

The design of newer electronic gadgets is making this task easier, Navarro says. “Now you can get the data by selecting ‘yes’ or ‘no’ on the inspection device, but it doesn’t end there,” he says. “When you do collect the data, you have to use that information for something.”

Also fleet inspectors frequently fail to check the obvious—tire pressure—which can be the root cause, for instance, of balding. By communicating illegible data, not doing proper inspections and overlooking tire pressure, fleet managers are not taking advantage of savings opportunities for longer machine life, Navarro says.

Condition-based maintenance, which is predictive in nature, is part of condition-based monitoring.

“Preventive maintenance (PM), as scheduled maintenance tends to be called, doesn’t prevent anything,” Navarro says. “As it is normally used, PM minimizes downtime only. However, predictive maintenance maximizes uptime. That is the major difference.”

CBM, because it is predictive maintenance, reduces machine life cycle losses and life cycle costs.

“Typical maintenance is based on a schedule,” Navarro says. “Scheduled maintenance is based on hours by the book or fuel consumption. Often, fleet managers wait for the component to fail. Then they know what is wrong and they can fix it.”

Condition-based monitoring, on the other hand, allows you to “catch impending failures early enough to save the component,” he says. Recent studies show predictive maintenance cost per horsepower per year is half that of reactive maintenance, he says.

Bill DeRousse, fleet service consultant for the City of Everett, Wash., says condition-based monitoring of equipment components is important to both the equipment owner and the equipment manufacturer.

In spec’ing public fleet equipment, managers want “to get the most reliable piece of equipment at the best price,” he says. “So, based on our experience and CBM, we require in our specifications that manufacturers’ brands have the longest life (parts and equipment brands) possible.”

By using CBM, DeRousse has found that the fleet clearly saves money, reduces billable time and, thus, reduces the cost to customers.

Today’s fleet manager has to be creative in how he conducts business, he says, and one of the reasons is a shortage of qualified technicians. “Managers have to determine how they can save money and yet maintain equipment in a safe and reliable condition,” DeRousse says.

In the past several years, CBM has become increasingly important in managing fleets, he says. “The economical downturn has forced fleet managers to do what they should have done years ago,” he says. “We have over-maintained our equipment for years. By using oil analysis, which is a critical tool in CBM, you can extend your oil change intervals and that saves a lot of money.”

Another benefit of CBM is that it helps improve equipment replacement cycles. “If you haven’t adjusted your replacement cycle either up or down in several years, it’s time to take a look,” he says.

Predictive maintenance

Kevin Reimert, CEM, fleet foreperson, Schlouch, Inc., says the term condition-based monitoring is not the same as condition-based maintenance, although that type of maintenance makes up the monitoring process.

“Basically, you have a piece of equipment that has several different compartments and components that you sample at a pre-determined interval set either by the OEM or the company,” Reimert says. “You take an oil sample and send it to a quality lab. The lab results generate a report relative to wear metals and other indicators.”

Another key part of condition-based monitoring is that you must have someone on staff who can interpret the report. Also, you have to develop a history with the machine.

“For example, say you bought a used piece of equipment and you sample the oil for the first time,” Reimert says. “You can’t base a decision on the first sample. You have to trend, and based on utilization, I would recommend taking a minimum of three sample reports. That gives you a consistency of use with the oil, a baseline to start trending.”

Another factor is to have a consistency with fluids. “If you jump around quite a bit—say, you use an OEM fluid and you switch to a fluid manufacturer’s products—you don’t have that consistency. Fluid consistency is important to track properly because different oil manufacturers use different additive packages.”

Reimert says the main benefit of condition-based monitoring is it allows fleet managers to be proactive rather than reactive with repairs. “The more you can be proactive, the less expensive the repairs get,” he says.

With a final drive, for example, an observed trend can minimize the cost. “You may end up replacing a complete set of bearings versus a complete failure, which could be 10 times the cost of a set of bearings,” Reimert says.

CBM protects capital investment, he says, which allows both employees and equipment to be in the field longer producing income.

Schlouch’s chief operating officer, Don Swasing, CEM, and director of site work services, cautioned that converting a fleet to condition-based monitoring takes time. “You don’t just jump from fix-when-fails to CBM in a week. We had to establish a baseline and do benchmarking for 48 to 60 months before getting there.”

CBM also protects the dealer, Swasing says.

“Rather than having something come apart and having someone say, ‘That’s under warranty,’ we don’t look at it that way. We can minimize the impact of catastrophic failure, and when we do that, it keeps cost down and maintains the Equipment Triangle.”

Swasing also credited Barry Schlouch, executive officer, with “having the wisdom” to recognize that operations play a key role in the success or failure of fleet management. As a result, Swasing says, Schlouch, “folded the ultimate responsibility for fleet performance under the chief operating officer.”

“He changed the structure,” Swasing says, “and with the change created the need for us to wear multiple hats to ensure good results on both sides of the house. There is no silo here between maintenance and field.”

CBM and lube management

“We spend more on oil today in cost per delivered gallon than we did five years ago,” Swasing says. “However, catastrophic failures have been dramatically reduced. Reliability is pulling our field unit cost down for delivered work. Maintenance work is very effective for the company, particularly during difficult times.”

Reimert says one misconception is that CBM can substantially extend oil drain intervals. “That’s not necessarily the case,” he says. “A standard OEM interval may be 250 hours. You hope you can extend that to 400-500 hours, but that is not always the case. The 400-500 hours is your target. That’s where you’re headed. It took us five years to get there.”

John Dolce, fleet specialist for New York-based Wendel Duchscherer Architects and Engineers, defines condition-based monitoring as “not scheduling a vehicle for maintenance by time, hours, mileage or fuel, which are the standard ways.”

“With CBM,” he says, “you leave the equipment in the field. When a sensor identifies a problem, you make a conscious decision to have a field person check it out, bring it in to a dealer or have the dealer send out people to inspect and repair the vehicle, or you bring the equipment home.”

A major benefit of CBM is that you don’t have to schedule a crew to go where the equipment is located, he says. “CBM keeps the equipment in service, and when it indicates the start of a problem, that’s when you send somebody to inspect it, identify what the problem is and take corrective action. Small problems, small solutions. Big problems, complex solutions; and complex solutions are extremely difficult to manage.”

Online predictive maintenance, Dolce says, helps machine performance because it is accurate. “Things don’t slip through the cracks,” he says. “It pinpoints where to look, and when a crew goes to the machine they take laptops that identify the issue. In most cases, the problem is simple, such as a corrosive wire. Very seldom is it a major component that has to be changed.”

CBM keeps cost down, keeps control of maintenance and doesn’t interrupt operations, all of which increases productivity. It also eliminates the time it takes to pull the machine out of service and later return it to active duty.

Another CBM benefit is that it allows the technician to travel to the equipment prepared for the repair.

“When he goes out to the worksite, he knows in advance what parts he needs to take with him to make the repairs,” he says. “Suppose a defective starter or alternator is diagnosed in the early life of a vehicle. The technician can take the core out, replace it, rebuild the old core and use it on another vehicle.

 “Cores are about 50 percent of the price of a new part. If you have a $1,000 part and you catch it before the core deteriorates, you save $500. Also, rebuilding a core is half the cost of a new one and three-quarters the life of new, so it’s really the way to go.” he says.

 “Technology has really helped maintenance, particularly with telemetrics and condition-based monitoring,” Dolce says. “It has extended vehicle life, increased the productivity cycle of the equipment and, just as importantly, OEMs are now building better machines that have longer lives.”