Equipment Type

Preventive Maintenance Inspections Prevent Premature Failure

Preventive maintenance inspections are simply a straight-forward, systematic approach to checking the condition of vehicles or equipment at planned intervals. They can be measured in several ways: by time, mileage, hours of operation, fuel consumption, or a combination of all four that best suits the needs of an individual fleet.

August 01, 2007
Inspection Checklist

Equipment inspections should be performed by drivers or operators on a routine basis and periodically by fleet mechanics. As part of these inspections, a visual inspection should include the following:

  • Tires, wheels, steering, suspension, drive systems
  • Coolant, exhaust, fuel systems
  • Lights and other electrical system parts
  • Leaks, both liquid and air
  • Body damage, both accumulated and new
  • Mirrors, interior and exterior
  • Brakes, service and parking
  • Windshield wipers
  • Instruments and gauges
  • Coupling devices
  • Safety devices
  • Emergency equipment

Source: AEMP


Four Categories of PM

Of course, it depends on what type of maintenance is being performed, service intervals and vehicle mileage or machine hours operated, but preventive maintenance usually falls into four categories.

PM-A involves minor maintenance work that is performed every 4,000 to 15,000 miles or one or two months apart. This work could include such things as lube jobs, vehicle inspection, or tire inspection and inflation.

PM-B covers maintenance service that is performed less frequently and is more complex than PM-A. Adjustment in engine performance or oil and filter changes would fall into this category. Service intervals in PM-B could range from 6,000 to 20,000 miles or two to four months.

PM-C encompasses more complex maintenance service, such as minor and major component testing, brake overhaul and replacement, fuel injector overhaul and replacement, and driveline adjustments. Maintenance in this category occurs between 25,000 and 40,000 miles or every six to 12 months.

PM-D is the category for major, planned jobs. This maintenance pertains to work such as in-frame or out-of-frame diesel engine overhauls or replacing or rebuilding gasoline engines. Service in this category generally is performed between 75,000 to 250,000 miles or 16 to 24 months.

Source: AEMP


Costing Out PMI

In determining the cost of preventive maintenance inspection programs, it's easy to feel like an overworked juggler in a cheap circus.

Factors for consideration are myriad, including geographical location, the type of vehicles contained in the fleet, the terrain of the various jobsites and, of course, the climate. But costing out PMI can be done regardless of the different types of equipment in the fleet or the number of vehicles operated.

Using the KISS principle (Keep It Simple, Stupid) here is an example of how to do it. Suppose you spend $1 per mile for maintenance with 30 cents per mile going toward scheduled maintenance and 70 cents per mile toward break-downs, or unscheduled repairs. If preventive-maintenance costs were increased to 35 cents per mile, then break-down maintenance should be reduced to 60 cents per mile, which is 5 cents per mile reduction in overall maintenance costs.

But numbers aside, the base line of establishing a PM inspection program still comes down to experience. If past experience tells you that certain repairs are needed at clearly defined mileage or hour intervals, do them. Otherwise, you should not perform strictly preventive overhauls.

If you notice, in reviewing the maintenance history of a particular machine, that the shop has adjusted the clutch on three almost back-to-back occasions, pay closer attention. You might need to replace the clutch. The idea is to make repairs before they cause even more damage or result in costly machine downtime.

A good rule of thumb when focusing on any PM inspection program is that scheduled maintenance should be targeted at 60 percent PMI, 30 percent direct inspections, and 10 percent component repair and replacement.

As for the costly unscheduled maintenance, it goes without saying that it should be kept to a minimum, although you'll never eliminate it altogether. Such repairs can be measured three ways: in terms of cost per mile, cost per hour, or cumulative cost to date.

As is the case with other managerial functions, maintenance has to be measured and managed. You may be able to outsource the work, but not the responsibility and accountability.

Source: AEMP

PM inspections are intended to identify problem areas and prevent premature failure caused from conditions such as lube fittings that aren't taking grease, lines that are worn, frayed and exposed electric lines, leaking fluids, and any part that is broken or worn out. They should be viewed as part of the overall maintenance program.

The foundation of a successful PM inspection program rests on dual cornerstones: consideration of manufacturer's recommended service intervals and a thorough understanding of the daily operating conditions of the machines. Equipment operating conditions include jobsite conditions, temperature ranges in which the unit works, and whether or not the unit is being used continuously.

"PM inspection programs vary by description from place to place," says Levi Dungan, CEM, owner of Dungan & Co. Dungan writes equipment appraisals. "It could be something as mundane as a daily operator inspection or something as detailed as a periodic inspection by trained technicians."

Although inspection programs can start with OEM recommendations, Dungan says the fleet professional needs to customize his approach. For example, there are differences in a program that is set up based on hours and a program based on fuel consumption.

"The hours-based program doesn't take into account how hard the machine has been working," he says. "Yet an hours-based approach is probably easier to maintain. It also more accurately reflects most equipment manufacturers' recommendations."

A consumption-based program is a more accurate representation of how hard the machine works, he says, although it requires accurate fuel records. Dale Warner, CEM, has implemented a fuel-consumption-based program at CJ Miller.

PMs for the company's over-the-road vehicles, as required by Department of Transportation regulations, are based on mileage. DOT mandates that inspections be done before the vehicle reaches 25,000 miles. Off-road equipment PMs, however, are done based on gallons of fuel used.

"Everything we do here as far as PM is concerned is by fuel consumption," Warner says. "By setting up a severity-based program, we are able to manage our PMs by workload rather than by hours. The more fuel a unit uses, the harder it is working, and that will determine the frequency of the PM."

Warner uses two preventive-maintenance categories. One is PM-A, which includes a visual walk-around. "We check to make sure everything is adjusted right," he says. "We do ongoing undercarriage inspections, tire inspections, and we take oil samples."

PM-B inspections are done when a unit is brought into the shop. "We do pressure checks and air-conditioning checks, for instance," Warner says. "If we had more time and more people, I'd probably break PM down into even more categories."

To manage such programs requires appropriate software. Although a number of different software packages exist for evaluation, Warner says the key aspect is that it includes the type of inspections you want. Most fleet-management software even has the capability to set up a PM inspection program.

"You can probably set it up within the fleet software you are already using," Dungan says.

Warner starts with information contained in manufacturer service manuals and uses that input as a base. "When the software kicks out the results, it is still itemized, but it's itemized by what we want done, such as filter replacement or whatever it might be," he says.

Scheduling is as important as the inspections. "You need specific people to do the regularly scheduled PMs, including such things as changing oil, filters, and pulling oil and coolant samples," Dungan says. And even more important, he says, is to create an environment where these things are not an option. They must be done.

"I'm a believer that the people who actually do the PMs should not be working for the guy who is responsible for break-down repairs," Dungan says. "My reasoning is that it is too easy to pull someone off an oil change to fix a broken hose and let the oil change go."

Somebody has to be responsible for ensuring the PMs are actually being done, says Dungan. "How you go about doing that isn't easy to define, but somebody has to be accountable. I'd have a separate supervisor responsible for making sure PMs are done on time and correctly."

Dungan says managers also have to ensure proper follow-up for problems uncovered during PM inspections, specifically those determined through oil analysis.

"The PM manager may receive a report on a sample taken 40 hours after a repair and the levels are normal," Dungan says. "Few managers have time to sit down and track such things as how many PPM of iron is normal for every 100 hours of operation of a machine. The reality of the matter is that the equipment manager, or the PM manager, is probably only tracking the exception reports. When a report comes back as normal, he probably doesn't even read it."

Dungan says that someone must analyze these reports, following up on them to make sure the problem was resolved.

"You might have two master mechanics on two separate jobs," he says. "The first one may have made a repair based on information from an oil-analysis report and thought he had fixed the problem. In the meantime, the equipment might be moved and the next mechanic gets the next report. Depending on how good your records are, he might not even know what the first guy did." What it all boils down to, says Dungan, is having one person to track these reports and keeping good records.

Done well, preventive-maintenance inspection programs combine manufacturer recommendation with fleet history to keep machines up and running.

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