Pierce Pumper, Operation & Maintenance Manual

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OPERATION
3-36 / Pierce Pumper
© 2019 Pierce Manufacturing Inc. All Rights Reserved.
3-15. Monitoring Intake Pressure
The master intake gauge shows the intake manifold pressure.
1. Watch intake pressure.
Look often at the intake pressure on master intake gauge while pumping.
2. Maintain 20 PSI intake pressure (pressurized supply).
Maintain intake pressure at or above 20 PSI when operating from a pressurized external supply.
This provides a safety factor to avoid drawing a vacuum on the intake hose.
Changes in supply pressure can cause intake pressure to drop without warning. Drop in pressure below zero
(0) PSI can cause water hammer, pump cavitation, or collapse the intake hose AND cause loss of water flow.
NOTE: 20 PSI may not be attainable in certain areas, depending on the hydrant system. For additional
information, consult your Fire Department standard operating procedures.
3. Maintain 20 in. Hg. vacuum (draft supply).
When operating from draft, always maintain 20 in. Hg. of vacuum or less. Intake vacuum of more than 20 in. Hg.
can cause pump to cavitate.
4. Avoid pump cavitation.
Pump cavitation is happening when:
— Discharge pressure changes up and down.
— You hear a sound like gravel churning in the pump.
— Discharge pressure remains the same when you change engine speed.
Reduce discharge flow until cavitation ceases.
Maintain positive intake pressure with soft intake hose.
Negative intake pressure will collapse soft intake hose.
Attack lines will lose water pressure if hose collapses.
Loss of water supply will endanger fire fighters on attack lines.
NEVER cavitate pump.
Low intake pressure or high vacuum can cause pump cavitation.
Cavitation can:
•
Cause loss of water pressure.
• Damage pump components, requiring expensive repairs.
Avoid water hammer.
Water hammer can damage the pump system.