Algas SDI VAPORAIRE M-Series, Operation & Maintenance Manual

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Operation
4-34
Algas-SDI Operations & Maintenance Manual – P/N - 54264
Figure 13 - Typical Venturi Performance Curve
Venturi Performance Curve.wmf
The factory set
MOTIVE PRESSURE
is the point at which the venturi performance
yields the leanest mixture at rated output and discharge pressure, when installed
at elevations up to 2000 ft.
Increasing the motive pressure beyond the factory setpoint will increase the
venturi output, while also putting a greater demand on the vaporizer. Increasing
motive pressure beyond the setpoint should only be done when required, with
caution to avoid overdrawing the vaporizer and increasing the mixed gas
HEATING VALUE CONTENT
.
As the elevation exceeds 2000 ft., the atmospheric pressure reduces to the point
at which the venturi may not achieve lean mixed gas heating values at the full
rated discharge pressure. When this is the case and a leaner mixture is
required, the discharge pressure (mixed gas pressure setpoint) should be
reduced while also slightly decreasing the motive pressure.
A general rule for discharge pressure reduction based on elevation is:
1 PSI/2000 ft.