Draft limiting factors, Pumping from draft – Hale 2CBP User Manual
Page 14
Sec II- 2
Operating Procedures
Booster Pumps
11. Advance the engine throttle gradually until
the master discharge gauge indicates the
desired pressure.
DO NOT REDUCE THE PRESSURE ON
THE INTAKE GAUGE BELOW ZERO;
SERIOUS DAMAGE TO THE WATER MAIN
COULD RESULT.
The master intake gauge reading must be
maintained at 5 PSI (.3 BAR), minimum. If the
gauge shows a vacuum the pump is attempting
to draw more water than the hydrant can
supply. When this occurs, reduce the pump flow
to increase the pressure.
As the throttle is opened, the pressure gauge
reading increases with the engine speed. If the
engine speed increases without an increase in
pressure, the pump is beginning to cavitate.
Close the throttle slowly until the pressure
begins to drop, and the engine returns to an idle.
12. Set the automatic relief valve according to
department policy. If no department policy
exists, refer to the Relief Valve Procedures
later in this section.
13. If the pump overheats and it is not equipped
with a Hale TRV valve, open the valve to
access the bypass line, if it is furnished, or
open the valve to the booster tank (both
suction and discharge sides) to circulate
water.
14. After completion of pumping operations,
gradually reduce the pump pressure until the
engine is at idle speed. Disengage the PTO.
DRAFT LIMITING FACTORS
The effect of raised water temperatures when
pumping from a positive pressure source
(hydrant) is negligible on fire pump
performance. But when pumping from draft,
elevated water temperature does have a limiting
effect. Water temperatures above 95
o
F (35
o
C)
will cause a noticeable decrease in lift when
drafting. Another factor that can limit lift when
drafting is barometric pressures below 29 In of
Hg. It is important to be aware of environmental
conditions when drafting.
PUMPING FROM DRAFT
1. Get as close to the water source as possible.
The pump can draw 100% of its rated capac-
ity with less than a 10 foot vertical lift. As the
lift increases to above 10 feet, the pump
Water Temperature
F
o
(C)
Lift Loss
Head Ft (Meters)
60° (16°)
NFPA Baseline
70° (21°)
.3
(.09)
80° (27°)
.6
(.18)
90° (32°)
1.1
(.335)
100° (38°)
1.7
(.52)
110° (43°)
2.5
(.76)
Table 2-1 : Additional Losses Beyond
Baseline NFPA Rating
Figure 2-2: Pump Operator's Panel