Electric Motor Driven Gas Compressor Unit

You don't say the application of where it will be used. Gas compressors are great if you don't have the electrical service available but more than double the wear of machinery. That means more moving parts to break. Depending on the use and maintenance some last longer than others but in my opinion you can't beat the use of electrical compressors. They don't have to warm up as long and you don't have to go get gas for them or change the oil as much. They are easier to work on when they do break. And they will all break. Good luck.

"Gas compressor units in single blocks, with compressors and high-speed motors driven"

Do you refer 'Three-pinion Gearbox' configuration, usually with three stage centrifugal compressor as 'gas compressor units in single blocks, with compressors and high-speed motors driven'? And want to compare (as mentioned) with traditional schemas of compressor units with electric motors operating separately from a compressor?

I am not sure what you mean by 'Gas' compressor drive. Is it a compressor driven by a separate internal combustion (petrol/liquid petroleum gas/diesel/gas turbine?) engine as versus an external electric motor?

With these external drives it is easier to repair just the item that has failed than is a combined electric motor and compressor (e.g. a semi-hermetically sealed refrigeration compressor). However, we usually send semi-hermetic units away for complete unit refurbishment and keep a refurb'd spare so that we can swap the whole unit over. That way we start with an 'as new' compressor and motor and drive (although the drive is so simple as to be almost irrelevant from the reliability/wear angle) rather than just a new motor or compressor or drive.

With the separate motor/drive there must be a shaft seal that is usually the least reliable item in the compressor and prone to cause loss of refrigerant (not so much of a problem with an air compressor). It is not usually that difficult to replace a shaft oil seal so it is not a huge disadvantage but that is where the semi-hermetic sealed unit gains as it is much less prone to leaks. Oil pumps tend to fail more often than the rest of the unit but are changeable without replacing the whole unit.

If you don't have a suitable electricity supply then having to generate electric to drive the semi-hermetically sealed compressor is probably no better than using the generator engine to drive the compressor more directly.

It can come down to what you prefer or what support service is available.

When it comes to selecting a compressor for natural gas compression, rotary screw compressors offer many advantages. Thanks.