Having reliable equipment is critical to every waste hauler. Ensuring that the correct tasks are done well and on time can prevent losses—both in equipment and job delays.
By Preston Ingalls
A major objective in maintenance operations is to reduce unplanned maintenance by increasing planned maintenance. Emergency labor, expedited parts, equipment downtime and lost production generally costs four to five times more than planned maintenance. As Figure 1, illustrates, Preventive Maintenance (PM) is one of the methods that helps us to migrate away from unplanned maintenance or Emergency Maintenance (EM), by doing more PM and Corrective Maintenance (CM).
The P-F Curve
As illustrated in Figure 2, the P-F Curve shows that most failures can be detected in advance if inspection is conducted at a frequent basis. The P-F Curve is a model that illustrates how components degrade over time and, therefore, left undetected and uncorrected, will run to Failure. Generally, when most components fail, it causes the equipment to fail. The curve illustrates that as the part begins to degrade, the equipment may deteriorate to the point where it can possibly be detected as the Potential (P point) for Failure. If the Failure goes unchecked, it continues on until the Failure occurs (F point). The period of time between P and F, commonly called the P-F interval, is the window of opportunity during which an inspection can possibly detect the pending failure and resolve it through corrective action. This allows us to inspect to detect, detect to correct and correct to perfect.
Preventive Maintenance provides that scheduled interval to conduct this check or inspection. By conducting routine services at certain hours or mileage intervals, we have the opportunity to ensure that the individual at-risk components are still to spec (within OEM specifications). We perform other activities at that time such as lube services, adjustments, filter changes, etc., but the most important activity is to take that window of opportunity and inspect to ensure the wear parts and condition are still acceptable or within the tolerances the OEM recommends.
P1, P2 and P3, shown on the curve, are Condition-Based Maintenance or Predictive Maintenance (PdM) and Preventive Maintenance inspection activities applied by maintenance personnel to detect early changes in condition. P4 and P5, which are closer to the failure event, and, therefore more easily detectable, are activities operations personnel can apply. Operators, using their senses, can detect 70 to 75 percent of all changes in condition before failure occurs. This is the main advantage of having an Operator Care program as part of the PM process. Operator Care is a structured process to formally engage the equipment operator is basic frontline upkeep or maintenance. Through the posting of laminated standards showing where tasks are performed, to several hours of formal hands-on instruction, to random audits to ensure compliance, to rewards and recognition to encourage compliance, Operator care takes the normal unsupervised responsibilities up several notches. The equipment operator is trained to perform daily and weekly CLAIRE tasks, which stand for Cleaning, Lubricating, Adjusting, Inspecting, Repairing (minor items), and Eliminating (recognizing and reporting changes in conditions). Since 70 to 75 percent of all failures can be detected by a well-trained operator, this formalizes the process to improve equipment uptime.
Preventive Maintenance, the foundation to a “Best in Class” Maintenance Program, is designed to improve and extend equipment life and avoid any unplanned maintenance activity. Its purpose is to minimize breakdowns and excessive depreciation. In its simplest form, Preventive Maintenance can be compared to the service schedule for an automobile or truck.
It includes activities such as lubrication, painting, testing, cleaning, adjusting and minor component replacement, aimed at extending the life of the equipment. The costs of operating this type of program are easily justified by the resulting decreased number of equipment breakdowns and delayed degradation of the overall material condition of the equipment.
Although PM can include multiple activities, the most important task in PM is inspection. Inspection helps to detect early signs of changes in condition—a warning of impending failure. The key to this inspection is making sure the equipment is “to spec.” In other words, the equipment and its components should be in a specified state or condition or within tolerance to do as it was designed.
To make this effective, PM procedures should clearly state what conditions we are looking for or not looking for. It should be stated as the “spec.” For example, it is inadequate to just state “Check belt.” That leaves too much to interpretation. A better approach would be to state the conditions you want to find the belt in or not, such as “free of glossing, cracks, fraying.” If it is not stated, you are leaving it up to the person who is performing the inspection, which provides too much variation in the tasks. Misinterpretation can create problems due to skill issue, lack of clarity or specifications, etc.
- Another example, a 250-hour PM on a Bobcat skid steer loader, shown in Figure 3, states specific inspection criteria. It also provides a recourse or corrective action (what to do if found out-of-spec). This minimizes misinterpretation by stating the desired condition or criteria.
The best means for developing a set of PM procedures is using the following:
- The OEM or manufacturers’ recommendation
- Examine the history of the equipment—look for patterns or trends that may require adjusting the task frequencies or tasks criteria—historical failures are a great indicators or future ones
- Use the experience and collective knowledge of the mechanics and techs to adjust tasks based on their own experiences with the equipment
Relying on the OEM recommendations as the only source can be a mistake because your conditions of use could be different than someone else’s. For example, your environmental challenges (weather, etc.) can be totally different than equipment used somewhere else in the country so “one size” does not fit all. This is why your mechanic’s experiences and your own history is far more valuable.
In refining a PM program, the key is to start with your most critical equipment first. Which equipment would shut you down resulting in the most financial loss? Start refining those tasks first.
How to Measure
It also means having good metrics to measure the effectiveness and results of your PM efforts. Example metrics or Key Performance Indicators (KPIs) include: percent PM of Total Maintenance Hours, percent PM Schedule Compliance, Mean Time Between Failures (MTBF) on Critical Equipment, percent PM Review (Revised PMs), percent Corrective Maintenance from PMs, and PM versus CM ratio. If your PMs are working for you, you should see the following:
• A reduction in unplanned downtime
• A 10 percent improvement in MTBF on Critical Equipment each year
• At least 50 percent of total maintenance hours as PM
• About one-fifth of all PMs generating some form of Corrective Maintenance work orders.
• And if you are doing them on time, you should be seeing 90 to 95 percent Schedule Compliance.
Replace the “Check this” and “Check that” with more specific specs. Having reliable equipment is critical to every waste hauler. Ensuring that the correct tasks are done well and on time can prevent losses—both in equipment and job delays.
With more than 46 years of experience, Preston Ingalls, President/CEO of TBR Strategies (Raleigh, NC), has led maintenance and reliability improvement efforts across 30 countries for a variety of companies. He consults extensively with heavy equipment fleets and the oil and gas industry in the areas of equipment uptime and cost reduction. For more information visit www.tbr-strategies.com.
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