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

How System or Back Pressure Affects Blowers

There is no compression or change in volume within the machine, but the blower works under system back pressure conditions. To illustrate, let us consider a case when the discharge of a blower is connected to the bottom of a tank (Figure 4), having water to a depth of eHf mm. The air-discharged accumulates in the discharge line until sufficient pressure is built (slightly over eHf mm of WG), when it starts to escape out. The system resistance or the static load on the blower is thus eHf mm WG. The power consumed by the blower depends upon the flow rate and the total pressure head on the blower.

The total pressure across the blower is taken as the pressure across the inlet and the discharge port of the blower. The pressure drop through inlet accessories and discharge accessories are a part of system drop.

In many cases of vacuum distillation applications, where the desired vacuum level is not achieved because of system inefficiency, it ultimately affects the product quality. Installation of booster pumps, which is comparatively a cheap proposition, often helps in improving the vacuum level under such circumstances. More in Vacuum Booster Pumps: Cost Effective and Power Efficient

Where Is the Catch?

Figure 5 indicates Pa as the ambient pressure. Pi is the pressure at the suction port, which is slightly below the ambient due to suction filter and silencer drop. Pressure Pd is the pressure at the discharge port of the blower and Ps is the actual system back pressure. As seen from the curve, the total work done by the blower is to raise the pressure of inlet volume from Pi to Pd.

Ideally, the blower is capable of resisting high pressures but the mechanical limitations, increased power intake, temperature rise and increase in eSLIPf restrict the working pressure head to about 7000mm of WG for air cooled blowers and 10,000mm of WG for water cooled blowers in single stage operation.

Taking a Closer Look at the Pressure Drop

It is, therefore, important to ensure that the drop between Pa and Pi (inlet drop) and and Ps (outlet drop) should be as low as possible. This can be achieved by using adequate size piping and large radius bends wherever possible.

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