It’s all relative: defining detectable versus random failures
When maintenance folks look out over their world, they don’t see rainbows and unicorns. They see a world of hurt.
The world they see is all kinds of possible ways machines and other assets fail to perform their jobs. Like police officers and emergency room workers who mostly see people at their worst, maintenance personnel see the underside of the plants, factories and fleets where they work. They see the results of abused, overused and under-maintained equipment first-hand.
Defining detectable versus random failures
Over the years, we’ve seen almost all the ways assets can fail. Some of those include poor maintenance craftsmanship, foolish equipment design, bad fuel usage, lack of maintenance leading to excessive wear, bad parts specifying and installation, as well as mis-operation, overloading and outright abuse. Trying to avoid all the causes of these failures are swirling around in our heads as we answer questions or work on the equipment.
These failures fall into two categories: failures that can be detected before they happen and ones that can’t. One failure that cannot be detected, for instance, would be a stone striking and breaking a vehicle windshield. Let’s refer to this as a random failure. An example of a failure that can be detected would be the destruction of a bearing due to misalignment or dirt entering the system.
These failures are the reason that even with “perfect” maintenance, there will always be breakdowns. Some of the failure modes don’t present themselves ahead of time.
These failure categories are not hard and fast categories for a couple of reasons. For one thing, the techniques to detect that failure might not be known or used within an organization. For another, the failure that cannot be detected now might be detectable in the future by one of the many new kinds of sensors or technologies that are being developed all the time.
Defense in depth
Overall, fleets will try their best to build and maintain robust items that can resist failure mode. For undetectable failure modes, fleets can take an approach called “defense in depth.” A defense in depth strategy means fleets can protect theselves from failure in several different ways.
Defense in depth originated as an information technology (IT) concept. The strategy behind this is to create multiple layers of security through redundancy. This means if one of the layers fails, there will be other security measures in place to ensure the entire system does not fail.
When used in a maintenance setting for vehicle equipment, each defensive line defends the vehicle. For the component to fail, all the defense lines must be breached.
A good example of defense in depth on a commercial vehicle is an air brake system. The braking system has fail-safes for air loss, redundancy and mechanical back-up. The system also includes audio and visual alarms, as well as a multi-point inspection process for drivers and maintenance personnel. Brakes have many defense mechanisms against the various failure modes.
Game changers for detectable failures
Preventive maintenance (PM) is traditionally part of the defense as well.
Fleets use PM inspections to detect components that are experiencing deterioration, damage or are defective. A PM allows a fleet to avoid the deterioration which leads to failure – for example, greasing bearings at regular intervals (I call it TLC: tighten, lubricate, clean). PM inspection is where detectable failure modes come into play.
As vehicle technology advances, OEMs continue to design equipment with built-in sensors that provide continuous monitoring. Sensors provide error codes in real-time, and the analytic software built into all modern equipment can provide a diagnosis or suggestion for service or repair.
With that, traditional PM practices for fleets will need to be updated. The sensors monitor vehicle systems much better, more frequently and less expensively than humans. While this may alleviate some of the workload for personnel, fleets will not be able to skip hands-on PMs altogether. In fact, hands-on PM becomes more important, because the inspection will be increasingly phased out and no one is there looking at the equipment. Hands-on maintenance inspections might be even more important in the new world than it was in the old world.
As the failure modes of your equipment swirl around in your mind, remember which can be detected by onboard sensors or PM inspection, and which failures can be postponed by hands-on PM. The world is out to hurt your equipment. Figure out how you can manage it.
Joel Levitt is the president of the Springfield Resources, a management consulting firm that services a variety of clients on a wide range of maintenance issues. Levitt has trained more than 17,000 maintenance leaders from more than 3,000 organizations in 38 countries. He is also the creator of Laser-Focused Training, a flexible training program that provides specific targeted training on your schedule, online to one to 250 people in maintenance management, asset management and reliability.
