The original life cycle bathtub curve was based on the cycle of human life. And at some point last century it was adapted by reliability engineers working in the electronics manufacturing industry to graphically represent the failure rate of their products. As you can see from its depiction below, the Observed Failure Rate-the top, bathtub curve, is the product of the three curves below it: Infant Mortality Failures, Wear Out Failures and a near constant rate of Random Failures.
One glance and it’s obvious the bathtub curve is just as pertinent to the life cycle of hydraulic components as it is to humans or electronic devices. And in a hydraulics maintenance context, it’s useful for framing our expectations and objectives. For example, we should accept that there will be some level of random failures resulting from manufacturing defects and circuit design faults. There’s not much we can do about manufacturing defects in a maintenance environment. But where analysis of a random failure indicates a circuit design fault, this can and should be rectified to prevent recurring failures.
In order to ‘flatten’ the bathtub and reduce the Observed Failure Rate, it’s necessary to flatten both the Infant Mortality Failure and Wear Out Failure curves. And when it comes to hydraulic components, maintenance has a significant influence. Hydraulic components are highly susceptible to having their ultimate service life compromised by improper installation and commissioning. But this is controllable. To the point where the only Infant Mortality Failures that are acceptable are those that result from a manufacturing defect or a circuit design fault. And as already stated, an infant mortality failure resulting from a circuit design fault should only be allowed to occur once on that machine.
Wear Out Failures are, to some extent, the nature of the beast. But there is much that can (and must) be done if this curve is to be as low and flat as possible. For hydraulic components this has many dimensions. It would be wonderful if it could be conveniently encapsulated by one task or thing. I’ve managed to condense it down into a 146-page book, The Hydraulic Maintenance Handbook, but that’s as simple as it gets. That said, anything you do to defer the otherwise inevitable ramp of Wear Out Failures is a step in the right direction. And reading “Six Costly Mistakes Most Hydraulics Users Make… And How You Can Avoid Them!” is a great place to start.