By Robert Johnson
As a fleet manager, one of your primary goals is to keep your vehicles operational. Therefore, when a vehicle is in need of a service or repairs, your first objective is to ensure that the necessary work is promptly completed. When the work is done, the appropriate entries are made in the vehicle maintenance records and you move on to the next task.
If this is the way you operate your fleet, you are missing out on a great opportunity. The integration of a component performance analysis program into your fleet management system will help improve the quality of your fleet while reducing your maintenance and operating costs.
Why do parts fail?
A vehicle part is normally replaced for one of three reasons:
1. The part in question was worn out (full service life achieved).
2. The part failed prior to being worn out.
3. The part was damaged by an accident or misuse.
When you examine a part and determine which mode of failure occurred, you are entering into the world of component performance analysis. However, to be a useful tool for the management of your fleet, the analysis must be carried out.
When implementing a component performance analysis program, it is not necessary to consider every aspect of your fleet at one time. First, identify a limited number of components with high failure or wear rates and develop your program from there. Then, examine your records system — you will most likely find your current system does not provide the amount of necessary information to make a detailed study of component performance. If this is the case, you may be able to establish a separate records system using a spreadsheet program. Such a system may have to be populated and maintained manually, but it will demonstrate the value of a component performance analysis program, justifying an upgrade of your primary records system.
Specific information you need for your program will vary depending on the type of component being evaluated, but typical data fields will include:
1. Type of part/component being evaluated (tires, batteries, water pumps, etc.)
2. Specific make, model and cost of component
3. Installation costs (labor, shop supplies, etc.)
4. Date installed
5. Date replaced and reason for replacement (worn out, premature failure, accident or abuse)
6. Make/model of vehicle or equipment on which part is installed
7. Mileage/hours at time of installation and replacement
8. Vehicle/equipment application
9. Operating environment (if more than one environment is involved).
As your system develops, you may also want to capture information such as service intervals (for serviceable parts), interim wear rates (for wear components such as tires and brake components) and overall condition of the unit on which the component in question is installed.
Establishing a base line
One of the first things you need to establish for each general class of component (tires, brake pads, etc.) is a base line life cycle for any given application. When identifying an application, all units in the group are equivalent. For example, do not compare brake pad wear on a 1/2-ton supervisor’s pickup with a Class 4 service truck. Once you have identified a general application, break it down by vehicle or equipment make and model, operating environment and duty cycle (urban, suburban, rural, on- or off-road, etc.). Typically, the base line life cycle for a class of components in a given application is based on the average time between failures for a representative sample of components. After establishing a base line, you can determine the average cost per measurement increment (miles, hours, operating cycles) for that class of component.
Evaluating component performance
After accumulating enough data (typically at least 12 months), you can review your component cost per measurement unit. By comparing the unit cost of various makes and grades of components, you can identify those that will result in the lowest overall cost of operation for your fleet. The parts with the lowest initial cost do not necessarily result in the lowest cost per measurement unit. Also, higher cost “premium” components may not provide a positive cost benefit.
During your analysis, differentiate between the various makes and models of vehicles and equipment in your fleet. Also, consider factors such as equipment application, operating cycles and operating environment. The components that provide the lowest cost per measurement unit in one situation may prove to have the highest cost in another.
Evaluating premature failures
A premature failure is when a component has a significant failure prior to its established time between failures benchmark. Although it is up to you to determine what constitutes a premature failure, a number of fleets use a benchmark of one standard deviation from the mean (see a text on statistical analysis for an explanation of standard deviation). To avoid deep statistical analysis, establish a reasonable margin, such as 85 or 90 percent of the time between failures.
If the majority of premature failures associated with a given class of components are linked to a specific brand or model, you can assume the problem is directly linked to the product. Unfortunately, the issue is not always this clear-cut. Some of the failure conditions you will likely encounter include:
* Across-the-board failures associated with a specific operating environment
* Across-the-board failures associated with a specific application or duty cycle
* Failures associated with a specific make or model of vehicle/equipment
* Failures associated with a specific job (application and environment are not unique)
* Failures associated with a specific maintenance/repair facility.
When it is determined that a series of premature failures are associated with a specific condition, look closely at the condition to determine what is causing the failures. At this point, you begin move away from component performance analysis and into the related field of failure analysis. This aspect of fleet management will be reviewed in greater detail in the February edition of Fleet Affiliation.
Robert “Bob” Johnson is director of fleet relations for the National Truck Equipment Association (NTEA), Farmington Hills, Mich.
The NTEA offers its members free access to extensive vehicle engineering, specification and design resources. The NTEA also keeps members abreast of important regulatory changes. A wealth of free information is available on www.NTEA.com