HALE AP, Technical Manual

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3.5.3.2 During Operations
During operations, additionally consider the following to further avoid conditions that lend them-
selves to cavitation. Being aware of the pumping environment can contribute greatly to avoiding
cavitation. Use Table 5 and Table 6 to help predict lift losses when operations dictate pumping
from draft.
•
Do not increase the pump speed beyond the speed at which the pressure ceases to rise.
•
Monitor the water temperature. NFPA standards set a baseline of 60° F (16° C). Table 3 il-
lustrates the amount of lift loss as temperatures rise. If there is a marked loss of suction ca-
pacity, the pump may be near cavitation.
NOTE
When water reaches 90° F (32° C), the operator is likely to notice a marked de-
crease in lift.
•
Monitor barometric pressure. NFPA standards set a baseline of 29.9 inHg. See Table 5.
Table 5. Lift Loss From Barometric Pressure
Barometric Reading inHg (mb) Lift Loss In Head Ft (Head M)
29.9 (1012.53) NFPA Baselines
29.7 (1005.76) 0.2 (0.06)
29.5 (999.00) 0.5 (0.15)
29.3 (992.21) 0.7 (0.21)
29.1 (985.44) 0.9 (0.27)
28.9 (978.67) 1.1 (0.33)
28.7 (971.89) 1.4 (0.43)
• Know your elevation (especially in mountainous regions). NFPA standards set a baseline of
2,000 feet MSL. See Table 6.
NOTE
Location: The higher the elevation (height above sea level), the lower the atmospher-
ic pressure and less lift. See Table 6.
Table 6. Lift Loss From Elevation
Elevation Ft (M) Lift Loss In Head Ft (Head M)
2,000 (609) NFPA Baseline
3,000 (914) 1.1 (0.33)
4,000 (1219) 2.2 (0.67)
5,000 (1524) 3.3 (1.00)