SA+ Two Stage Series Two-Stage Screw Air Compressors

For plants with heavy air demand, the compressor room is often one of the biggest electricity users on site. In the cost structure of compressed air, the purchase price is only a small part; the real weight lies in the electricity bill over years of operation. Every gain in compressor efficiency, multiplied by round-the-clock running hours, becomes a substantial difference in cost.

The Fusheng SA+ two-stage screw air compressor is built around exactly that. By splitting compression into two stages, it brings the process closer to isothermal compression and cuts energy consumption sharply — around 15% less than single-stage compression. The series runs at 0.7~1.25MPa working pressure, with air delivery of 4.2~85.0m³/min and power from 55~450kW.

Why Two-Stage Compression Saves Power

Air heats up as it is compressed, and the hotter the gas, the more work it takes to raise it to the same pressure. Ideally the compression process would be held as close to isothermal as possible — no temperature rise, minimum work.

In a single stage, structural limits mean the gas heats up considerably in one pass, so the real process departs a long way from isothermal. Two-stage compression works differently: the air is compressed to an intermediate pressure, thoroughly cooled, and then passed to the second stage. Two compressions and two coolings make the temperature curve of the whole process flatter, and therefore closer to isothermal. That is the fundamental reason two-stage compression saves power.

That is also why two-stage compression is not simply a single-stage structure cut in two. It calls for interstage cooling, sensible pressure distribution and a purpose-designed airend before the theoretical advantage of isothermal operation turns into a lower reading on the meter.

What an Around 15% Saving Means

According to Fusheng, the SA+ two-stage series saves around 15% compared with single-stage compression. On a single machine that figure may look modest, but for 55~450kW units running continuously all year in a compressor room, a 15% difference in electricity cost accumulates throughout the operating cycle and ends up as a considerable saving.

The actual saving will vary with duty, air demand fluctuations, piping condition and other factors, so selection is best supported by calculations based on real operating data rather than a single percentage applied blindly. Put another way, the energy saving is proportional to running hours: the longer the machine runs and the fuller its load, the shorter the payback on two-stage compression.

The Bigger the Machine, the More Reliability Matters

The larger the machine, the greater the impact a stoppage has on production. The SA+ series uses Fusheng high-efficiency airends, balancing the pursuit of efficiency with stable, reliable operation. For a compressor room, a steady continuous air supply is itself part of efficiency — the production losses caused by frequent stoppages are usually dearer than the extra electricity. Two-stage compression also demands more of airend design and manufacturing, and the actual quality of the airend determines whether the energy saving can be sustained over the long term.

Pressure and Air Delivery: Getting the Match Right

The ranges 0.7~1.25MPa and 4.2~85.0m³/min cover a lot of ground, but the maximum of each cannot be taken at the same time: for a given model, available air delivery falls as pressure rises. Selection should start by fixing the working pressure used most often, then matching air delivery at that pressure point, and setting model size and quantity from there.

Count Whole-Station Efficiency, Not Just the Machine

The efficiency of a single compressor is only part of a compressor room's energy performance. In practice, pressure set too high, piping leaks, insufficient storage volume and excessive pressure loss in the treatment stages all erode the savings an efficient model can deliver.

So when choosing an SA+ two-stage model, several things are worth doing at the same time: check the piping network for obvious leaks, confirm that storage volume matches the fluctuation in air demand, and check whether pressure loss through drying and filtration is reasonable. Optimising these together is what lets the efficiency advantage of two-stage compression actually reach the meter.

Technical Specifications

Industries and Applications

• Manufacturing compressor rooms with heavy demand and continuously running equipment;
• Textiles, chemical fibre and similar industries with steady, high-volume air demand;
• Heavy industry applications such as metallurgy and building materials;
• Centralised plant-wide air supply systems with relatively high per-unit power.

Selection Advice

1. Start with an air demand survey: total up the demand at each point of use and allow a sensible margin instead of relying on guesswork;
2. Set pressure by requirement: 1.25MPa is the capability ceiling, and actual selection should match the truest demand at the point of use;
3. Evaluate two-stage compression first for high-power machines: the greater the power and the longer the running hours, the clearer the return from energy efficiency;
4. Auxiliaries and piping matter just as much: drying, filtration and piping optimisation directly affect the actual energy consumption of the whole station.

Conclusion

Energy savings in a compressor ultimately have to come from the compression process itself. The SA+ series uses two-stage compression to push that process closer to isothermal, serves medium and large compressor rooms with a 55~450kW power span, and treats stability as a non-negotiable precondition for large machines. For users running high power over long hours, efficiency and reliability were never an either-or choice.