The idea that a piece of equipment breaks down because of the error of a single mechanic in installation or a single design error is nice – but usually it doesn’t hold up to scrutiny in the real world. The real roots are usually much deeper than a single metallurgical problem or one error on the part of the maintenance mechanic or even the fact that the machine is being run at twice the design load. When all the human errors and management system deficiencies are included, the typical machine breakdown is the result of somewhere between five and ten significant contributors.