Even greater energy savings with new variable speed compressors
July 27th 2006

Companies wanting to reduce their operating expenses should not overlook the cost of providing compressed air, which is a major item in the energy balance of most companies. Variable Speed (VS) screw compressors help reduce these costs significantly (up to 35% savings). VS screw compressors have been supplied by Gardner Denver since 1998, which has made the company a pioneer in this field.

The desire for a global product with class beating energy efficiency led to a radical approach to the latest design, with all aspects of energy consumption within the package being put under the spotlight.

THE SPECIFIC ENERGY CONSUMPTION IS REDUCED BY 13%

The energy/flow characteristics of the ENDURO-Plus profile air end are almost constant throughout the speed range. This contrasts with traditional air end designs that emphasize full speed capacity at the expense of part load efficiency, so important with VS compressors.

The main drive motor (insulation class F, IP 55) and inverter package has a very high efficiency across the full speed range, plus a flexible drive coupling eliminates belt drive energy losses. Depending on the rating and age of a machine, a vee-belt drive can account for a loss of between 1.5 and 2.5 %.

Throughout the life of the direct-coupled machine, these savings accumulate dramatically. "Lifetime energy costs far outweigh initial purchase costs, and users are now starting to realize the importance of this in their decisionmaking " says UK manager Chris Smith.

Typically, a temperature dependant wax element would control the oil flow. But this element does not consider the intake temperature and so is imprecise, slow to respond especially when the machine is cold. The proportional oil mixing valve in the new, direct-coupled VS screw compressors avoids these drawbacks, such as increased wear and tear of the oil, degradation of the oil quality and higher corrosion risk. This results in the best thermal efficiency in the air end without the possibility of condensation. "We designed the highest possible operational safety, economy of operation and service life in the new VS machines", manager Smith underlines.

LOWER NOISE LEVELS

For optimal efficiency of the cooling air, the new VS compressors have separate flow paths for the air intake, cooling fan and inverter. The result is extremely low noise levels, 64 dB (A) at part load.

All in all, with these changes, the new direct-coupled VS series from Gardner Denver is 13 % more energy efficient. "We realized that the new direct-coupled VS series of compressors will be a global success not only because of compelling technology but also because of the excellent value for money that they represent, both in terms of capital cost and lower energy consumption. Energy comparisons between competitive VS compressors will determine purchasing decisions in the future" commented UK manager Chris Smith.

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