If you want to ensure equipment reliability at the lowest possible cost, you have to plan for it. With any asset, you need to address the following questions:
What is the equipment function? The primary function? The secondary function?
What is the desired performance?
How long do you plan on it operating (i.e. service life)?
What will the operating context be (i.e. 24/7/365, tropical or frigid climate, abrasive process)?
What are the consequences of failure? How will you mitigate the consequences?
Have you identified the failure modes through failure modes and effects analysis (i.e. the Blow Out Preventer [BOP] with 260 failure modes)?
What is the probability of failure with any of those failure modes?
How will you find those prior to failure during the failure detection window?
What will be the mode of restoration (i.e. repair in place, replace, rebuild offline)?
How will you minimize the impact to production if you miss the failure in the failure detection window (i.e. mean time to repair or maintainability)?
Too often, there is no real plan as many choose to shoot from the hip. Take the time to create a strategy for your assets to attain increase reliability.