IGV or IBV ? , that is the question…

In the 20th Century inlet butterfly valves (IBV) on centrifugal air compressors were the standard. But as there came more demand for better energy efficiency the application of IGV’s rose.

IGV stands for inlet guide vanes, this technology was adopted from the turbine industry. IGV’s are providing more energy savings on centrifugal or so called turbo air compressors. The need for more energy savings has become even more in the last decade. Resulting in IGV’s becoming the standard in centrifugal air compressor technology.

Working principle of the inlet butterfly valve:

The IBV directs the airflow in a more or less straight line to the first stage of compression. The impeller then spins the air using power from the main motor. Increasing the air speed and directing power to the diffuser part of the compressor.

When the IBV is partially throttled (closed), the inlet pressure is reduced, losing some of the available static pressure. The pressure ratio of the total compressor must now be greater to meet the same discharge pressure. This will result in more power consumption by the compressor package as a whole.

Working principle of the inlet guide vane:

Unlike the IBV, the IGV has multiple triangular blades that allow the air to flow into the compressor in a swirl direction. This “pre-swirl” air reduces the amount of power required from the main motor to spin the air entering the impeller. The directional flow increases as the vanes close, putting less load on the impeller compared to a butterfly valve. This makes inlet guide vanes more efficient during turndown than inlet butterfly valves.

The main benefit of using an IGV over an IBV is the reduced energy consumption gained from throttling the air compressor. Centrifugal air compressors are designed to operate at the highest flow conditions in the range of 60 to a 100% throttle range. This is the ideal range to apply an IGV.

IGV’s can save even more energy when the compressor is running at a throttled angle, which offers considerable power (kW) savings. When looking at the IGV and IBV power charts, it demonstrates the following.
An compressor operating with a throttled IBV at 72% of the full (design) flow, will have a power consumption of an equal 72%. Under the same conditions, an compressor operating with a throttled IGV at 72% of the design flow, will now has a reduced power consumption of 63%. The result is up to 9% power saving. This is a direct saving on the energy bill.

We at RTC Group take full use of Inlet Guide Vane Technology in our oil free rental air compressors. Resulting in power savings during your temporary need of high quality, oil free compressed air.