As energy costs continue to outstrip other business input expenses, it’s more critical than ever to find new ways to save power. Two-stage compressors may just be one of the answers.
“Many customers get fixated with the capital cost of an air compressor, and whilst those that want to save energy costs will look a little deeper and review service costs, very few understand the long-term total operating cost of compressed air,” said Southern Cross CEO, Mark Ferguson. “The largest cost related to producing compressed air is in energy, and this typically represents the highest energy usage in the plant. With continuously rising energy costs, it’s an area in which businesses can readily address to achieve substantial potential savings. Two-stage compressors really are low-hanging fruit.”
A single-stage compressor typically used in industry is limited by the overall compression ratio across a single airend. This compression ratio in most industrial applications is around 9:1 according to Ferguson. High compression ratios, particularly as pressures increase, results in significant internal slippage which leads to loss of capacity and a reduction in efficiency. A high compression ratio also means higher bearing loads as the elevated internal pressures and temperatures mean greater axial and radial bearing loads. This can limit airend bearing life which can lead to significant long-term maintenance costs.
A two-stage compressor, on the other hand, allows the compression ratio to be split over two distinct rotary screw airends resulting in compression ratios across each airend of around 3:1. The outcome is less slippage, reduced bearing loads and, with intercooling, significantly higher outputs for the installed motor power. The output of a two stage compressor is typically around 20% higher than that of an equivalent singe-stage compressor.
To put that into perspective, energy savings mean generally one size smaller compressor and in most instances a return of the difference in capital cost in only a matter of months. Combine this with a VSD controller, where demand varies significantly, and savings can be even greater.
As a division of one of the world’s largest and most innovative compressor manufacturers, Southern Cross offers the latest in two stage technology built on traditional heavy-duty design platforms with components produced to last. When combined with a structured service program, the Southern Cross range of two-stage compressors enjoys a five-year package warranty with a unique, lifetime warranty on the screw airends. From 75kW to 355kW, all Southern Cross two-stage compressors are available as fixed or Variable Speed Drive (VSD) controls.