ASC -Blower Surge White Paper0 pages

APPLICATION SHEET

SURGE IN AIR SUPPLY SYSTEMS

A. BLOWER SURGE

When a blower is used in the capacity range for which it was designed, surging (pulsation) is seldom a

problem. There are certain applications of blowers, however, where it is necessary to keep the blower

running during periods of very small demand. These turndown periods may call for as little as 10-20%

of rated volume output of the blower. In such cases, surging can set up a pulsation which may disturb

the process and cause overheating and consequent damage.

The Pressure vs. delivery Curve typical of Hauck blowers is shown in figure 1. Note that the pressure

attains a maximum high point at some relatively low rate of output. The curve rises at air delivery rates

below the critical value and descends at rates above the critical value.

Fig. 1

If the demand on a blower is decreased in volume from a normal operating point, A, to another

operating point, B, but still above the maximum pressure point, E, to a very low point, such as C,

surging may result due to the following sequence:

1. The blower delivery pressure first decreases from E to c at the blower itself.

2. For a moment, pressure in the piping system connected to the blower is greater than the

pressure at the blower itself.

3. Thus, the air in the piping line reverses direction and flows back into the blower until both

pressures are equal.

4. When pressure equalization has been achieved, the blower again resumes its normal function

of pumping air into the system.

5. When the restriction at the line outlet (the burner) again reduces throughout, the entire

sequence repeats.

HAUCK MANUFACTURING CO., P.O. Box 90 Lebanon, PA 17042-0090 717-272-3051

5/86 www.hauckburner.com Fax: 717-273-9882

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