Understanding Blowers: How to Make the Best Use of Blowers and Compressors

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TURCK GmbH

EDL Anlagenbau Gesellschaft mbH

Everest Blower Systems

The blowers are generally selected for the maximum system pressure, which they may encounter during operation and the prime mover is selected accordingly. When in operation, the blower offers a considerable power saving – since the power consumed by it depends on the actual working pressure under which it operates and not the rated pressure.

Typical performance curve (Table 3) shows the characteristics of Roots blower. In a reciprocating or vane type compressor, the compression ratio is fixed and the suction air is compressed – according to the compression ratio, irrespective of the load conditions.

A fixed power, is therefore, consumed by these type of compressors.

Generally used terms

Ambient pressure:

Absolute pressure of the atmospheric air in the vicinity of the blower

Absolute pressure:

It is the pressure measured from absolute zero i.e., from an absolute vacuum. It is the algebraic sum of the atmospheric pressure and gauge pressure.

Gauge pressure:

Pressure measured above the atmospheric pressure

Static pressure:

It is the pressure of the gas measured in a manner that no effect due to velocity of gas stream is recorded.

Velocity pressure:

It’s the pressure solely due to velocity head.

Total pressure:

It is the total system pressure i.e., sum of static pressure and velocity pressure.

Pressure ratio or compression ratio:

It is the ratio of absolute discharge pressure to absolute inlet pressure.

Swept volume of blower:

It is the volume, that is swept by one revolution of the blower.

Actual volume flow rate:

Actual volume flow rate of gas compressed and delivered at the standard discharge point, refers to conditions of total temperature, total pressure and composition, prevailing at the standard inlet point. Also, referred as FAD (Free Air Delivery), at inlet conditions.

Standard volume flow rate:

Volume flow rate of compressed gas as delivered at the discharge point but referred to standard inlet condition of total pressure, total temperature, and composition (1 bar, 20oC, R.H. 36 per cent)

Normal volume flow rate:

Volume flow rate of compressed gas as delivered at the discharge point but referred to NTP condition of total pressure, total temperature and composition (1 bar, 0 oC).

Compressed volume flow rate:

Volume flow rate of gas at the discharge referred to conditions of total temperature, total pressure and composition, prevailing at the discharge point. This is generally not used.

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