Pierce Pumper, Руководство по эксплуатации и техническому обслуживанию

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Pierce Pumper / 3-39
OPERATION
Two-Stage Pump
3-17. Two-Stage Pump Operation
(Optional)
Two stage pumps have two smaller impeller chambers instead of one large chamber. Water is directed through both
chambers in parallel when large flow is desired at moderate pressure.
Water is directed through each chamber in series when moderate flow at high pressure is desired.
Read, understand, and practice the procedures for two-stage pump operation found in the pump manufacturer's
operation manual.
3-17.1 Select Either Volume or Pressure Mode
Figure 3-7: Typical Electric Transfer Valve Controls
POM0025, 0026
Shift the Transfer Valve to the VOLUME setting for high flow at moderate pressure.
Shift the Transfer Valve to the PRESSURE setting for moderate flow at high pressure.
3-17.2 Mode Selection with Pressurized Sources
NOTE: For departments operating with higher hydrant pressures:
• If the external intake pressure is high, then a pump in PRESSURE mode is able to run with
engine RPM slightly above IDLE to provide desired discharge pressure. In this condition, the
engine speed cannot be reduced enough for a pressure governor to react to pressure spikes
caused when discharge lines are shut OFF.
• To avoid such pressure spikes, operate the Two-Stage Pump in VOLUME mode. This causes
the engine to operate at a higher speed. The pressure governor then has more ability to control
pressure spikes.
Operate a Two-Stage Pump in the VOLUME mode when pump is supplied by a pressurized external water source
AND a pressure governor is used.