7.5 – 22 kW screw compressors

This is the size band most factories actually buy, so it is built to be left alone. The airend is direct driven, the cooler is oversized for hot climates, and the electrics are rated for the ambient the machine will really see rather than a laboratory figure.

Cooling air is drawn in low and pushed out high, so the machine is not breathing its own hot exhaust when it sits against a wall. In a Gulf plant room in August that single detail decides whether a compressor runs all day or trips at two in the afternoon.

Panels come off without tools and the service points are grouped on one side. An engineer can do a full service standing in one place, which is why these machines tend to get serviced properly.

The controller holds the machine at a pressure band rather than a single number, so it is not loading and unloading every few seconds when demand is light. That alone is worth several per cent on the electricity bill.

Running hours, load percentage, discharge temperature and the service countdown are on the home screen. Trend data is what an engineer reads, because a discharge temperature that has been climbing for three weeks shows on a graph long before it trips the machine.

It will run two machines in sequence and swap the lead unit on a timer, so both age evenly instead of one doing all the work while the other sits as an expensive spare.

Kits are made up by interval. Air and oil filters with an oil sample at two thousand hours, then the separator, the oil change and a cooler clean at four thousand, then a full performance check and a motor regrease at eight thousand.

The separator is the part most often bought on price and most often regretted. A cheap element raises the pressure drop across the vessel, and you pay for that difference in power every hour the machine runs.

Everything in the kit is to the specification the machine was performance tested on, including the fluid. Mixing fluids is the commonest cause of separator failure we get called out to, and it is completely avoidable.