Thursday, October 15, 2009

Inlet Guide Vaines

Inlet Guide Vanes
Variable Inlet Guide Vanes from Cameron's Compression Systems are an ingenious yet simple option that, when installed on your centrifugal compressor, can deliver energy savings of up to 9%. By replacing the standard inlet butterfly valve with a new guide vane assembly, substantial energy savings result whenever the compressor operates at less than full load or when ambient air temperature is less than design temperature (usually 95F/35C).

How does it work?
Unlike the standard butterfly valve, Inlet Guide Vanes impart a whirling motion to the inlet air flow in the same rotational direction as the first stage impeller. This reduces the work imparted by the impeller, thus less power is required to deliver rated air flow and pressure.

Low ambient temperature provides energy saving opportunity

Centrifugal compressors are designed to produce the required flow and pressure on the hottest day expected at their installed location. At lower ambient temperatures, the compressor can deliver more air at the same pressure. Since this additional air is not normally required, the compressor intake must be throttled to maintain only the capacity needed. By regulating with Inlet Guide Vanes, a substantial power saving can be realized over that possible with a butterfly throttle valve. And you’ll see that saving almost every day – every day, that is, when the temperature is below the design point.

3 Ways to Save!
Example 1. Save on cool days
Suppose a centrifugal compressor designed for operation at 95F/35C is running on a cold 30F/-1C day (refer to graph). At that temperature the compressor will produce about 20% extra flow at design pressure. If the unit is throttled back to the original design flow with the butterfly valve, the unit would require 97% of design power. But if the unit was equipped with Inlet Guide Vanes, the same condition requires only 92% of design power – a savings of 5%.

Example 2: Save when demand is lower
When plant demand is less than the full 100% design flow, the guide vanes regulate further, more pre-whirl is imparted to the air, and less horsepower is needed. If the flow requirement is 72% of design flow only 65.5 % of power is required using Inlet guide Vanes. Using a butterfly valve under the same conditions would require 72% of design horsepower. The difference represents a total net savings of 9%!

Example 3: Get more air when you need it
Inlet Guide Vanes can also allow you more air flow, when needed for the same rated power. Referring to the graph once more, the butterfly valve consumes 97% power at 100% flow. For exactly the same power, an additional 5% air flow can be obtained through the use of Inlet Guide Vanes.

How much money can you save?
Referring one last time to the graph, we saved 9% power running at 72% flow on a cold 30F/-1C day. If that compressor was a 1000 HP/746 KW unit, you could save $22,000 if you could run the compressor that way for a year.

But that’s not often likely. A much more realistic example would be if you never required less than full 100% flow, and if the average temperature for the year was 50F/10C. You would still save over $17,000 that year!

Recommended Upgrade For: Any centrifugal compressor using a butterfly valve to control flow into the first stage inlet.

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