Hale MBP Booster - Manual (Page 39)

❑ Operation
38 Silencer Series Booster Pump, p/n: 029-0020-83-0
Vacuum Compound Gauge
Do not depend entirely on the vacuum (compound) gauge to indicate when
a pump is nearing cavitation. The vacuum gauge is usually tapped into the
intake chamber several inches away from the leading edge of the impeller
eye where the greatest amount of vacuum occurs. The vacuum gauge does
not take into account ambient temperature nor atmospheric pressure and is
not accurate near zero (0) on the vacuum scale.
To Eliminate Cavitation
To eliminate cavitation, the operator must be aware of the warning signs
listed above. Low barometer, high elevation, and elevated water tempera-
ture also contributes to cavitation.
Pumps are rated at standard temperatures and barometric pressures.
When conditions vary from standard, the maximum capacity of the pump
from draft can be affected.
The most common way to eliminate cavitation is to decrease the amount of
water being discharged by decreasing engine speed or closing discharge
valves. However, this also results in a reduction of flow.
Cavitation is also eliminated by increasing the pump inlet pressure. This is
accomplished with reduced vertical lift, reduced inlet losses, or running from
positive pressure supplies.
During Operations
❑ Do not increase pump speed
beyond the speed at which the
pressure ceases to rise. The
higher the elevation above sea
level, the lower the atmo-
spheric pressure and less lift.
(See Table 3-6: “Lift Loss from
Elevation.”)
❑ Open the throttle gradually and
watch the pressure gauge and
the tachometer, if equipped.
An increase in engine RPM
without a corresponding
increase in pressure indicates
cavitation.
Elevation
Feet (Meters)
Lift Loss
Feet (Meters)
2,000 (610) NFPA Base Line
3,000 (914) 1.1 (0.33)
4,000 (1,219) 2.2 (0.67)
5,000 (1,524) 3.3 (1.00)
6,000 (1,829) 4.4 (1.34)
7,000 (2,134) 5.5 (1.67)
8,000 (2,438) 6.6 (2.01)
9,000 (2,743) 7.7 (2.35)
10,000 (3,048) 8.8 (2.68)
Table 3-6: Lift Loss from Elevation