Our article “Understanding
Sizing Factors for Centrifugal Separators” described what a
centrifugal separator is, the key design criteria required for proper sizing and
how to use our web-based sizing tools. In this article we explain the
sizing charts and formulas of which the web-based calculators are based upon.
The two articles combined enable you to both properly size a centrifugal vortex
separator and compare performance criteria of liquid removal and pressure drop
amongst several separator designs.
We use two charts for sizing separators, one for steam and another for all
other gases. We will review sizing for steam applications first because it
is more simplistic.
The sizing charts have a X, Y and secondary Y axis. The X axis lists
the mass flow rate of steam or the volumetric flow rate for air depending upon
the chart. The Y axis lists absolute pressure (PSIa) and the secondary Y
axis the corresponding differential pressure (∆P). The diagonal lines
across the chart are the performance curves for standard separator sizes.
Since centrifugal vortex separators have an infinite turndown ratio they
maintain their separation efficiency at lower pressures associated with start-up
and shut-down.
Moisture Separator Sizing for Air and Other Gasses
The procedure for sizing air and other gas applications is the same with
respect to drawing horizontal and vertical lines, the difference is that the
volumetric air flow needed to use the chart is the “Equivalent Air Flow in SCFM
(Qc)”.
Qsg is the rate of flow in CFM