Everything about machinery selection can be lumped into one of these three categories: Quality, Delivery, and Price. Whether a technical or “soft” issue, quality, delivery, and price should always be brought into the discussion.
As simple as it may sound, this entire process begins with having a thorough understanding of the project requirements. Input from operations personnel provides insight to operational deviations. For example, 95% of the time a gas gathering service in the upstream sector may carry an acceptable amount of water (or other liquids) entrained in the gas, but the other 5% of the time (18 days of a year) the amount of liquids in the gas is beyond the capacity of the scrubbing system, as initially designed. This additional liquid loading could be due to low ambient temperature, high winds, blowing snow, well treating chemicals, pigging of the pipeline, etc.
If a reciprocating compressor is applied here, the user may not be able to replace compressor valves as fast as they fail, or scrubber high level alarms won’t clear. Considering a centrifugal compressor with a water wash system, the end user may exhaust their reverse osmosis water supply, or the system freezes and there are extended periods without online washing. Alternatively a screw compressor is installed in a gathering service where a new well is tied in with a composition very different than the balance of the system. This can (and has) caused significant lube carryover problems and other lube issues that prevent the screw compressor from operating. In all cases, for one reason or another, the compressors won’t run reliably.
Ultimately, the end user has to make a technical compromise to select the best machine the project can bear that will be delivered and installed in the promised time, and without exceeding the budget.