Reliability Assessment: A Guide to Aligning Expectations, Practices, and Performance. Daniel Daley

When ordinary people purchase a new car, they address reliability in the very limited way, if at all. Apart from form, fit, and function, there are a number of integrity-related and reliability-related issues that purchasers typically choose to trust to others.

      A few examples involve features that particularly careful buyers may change after they purchase a new car because the design features are not readily available from manufacturers or dealerships. One example is tires. It is not uncommon for particularly careful people to go to a tire store immediately after leaving the dealership with a new car. Doing so, they are able to trade the almost new tires on the car for a set of new tires with which they are more confident. Another example is based on personal experiences with car enthusiasts who choose to “blueprint” new cars as soon as they are delivered. The process of blueprinting a new car is typically reserved for high value or collector cars. It entails disassembling a significant portion of the car looking for missing or loose connectors and for key settings that are misadjusted during manufacturing. These individuals have little trust for the typical factory worker.

      In either case, if it were possible to specify the way cars are assembled, some individuals would demand:

      •Different and better tires

      •Different quality control practices

      •A run-in procedure prior to delivery to eliminate components likely to experience infant mortality

      In most cases, however, car buyers would typically pick the color, the number of doors, and the kind of transmission and trust everything else to the manufacturer and the dealer.

      Moving beyond typical purchases made by individuals, examples of integrity-related issues may involve the adequacy of the structural design and assembly. The complexities of these issues are beyond the understanding of most non-engineers. Therefore, most people tend to trust that they are being handled in an appropriate manner, which is not always the case. Here are a few examples:

      •One of the major locomotive manufacturers chose to use an unqualified manufacturer for the pressure vessels containing high pressure air for brakes and other pneumatic systems. After these vessels began to explode without warning, the manufacturer implemented a program to replace them.

      •By now, you may be aware that several important elements of the design of the twin towers in New York were such that they jeopardized the integrity of the buildings’ structure in unusual situations.

      •It is unusual but not unheard of for a bridge to collapse. In 2007 the I-35W bridge spanning the Mississippi river in Minneapolis collapsed. The NTSB (National Transportation Safety Board) reported that a flaw in the design combined with unusual loading at the time of the collapse contributed to the failure.

      In each of these examples, the basic integrity of the system was taken for granted. Viewed purely from the ability of those systems to perform their intended function, they experienced reliability (as well as integrity) failures. From these examples we can see that integrity is a critical element of reliability.

      Despite the counter-examples described above, many design processes contain elements that adequately address the integrity-related issues that ensure the safety and functionality of the system being designed. When these elements are adequately addressed, they are accompanied by a measure of reliability that goes hand-in-hand with the integrity.