Fire Pump Theory

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Fire Pump Theory
Pump Types

• Section 180

Class 2
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Background of fire pumps
Over the past 200 years, legends have grown up
about antique fire apparatus. Old fire engines
or masheens as they were know, had to be
carried by hand. This machine had the essential
fire pump, a piston pump with a goose-neck
metallic pipe called a break. Firefighters would
move the break in an up down motion called
stoke, pumping water out of the apparatus to
combat fire. Modern technology has drastically
changed pump design. The centrifugal pump
replaces the positive displacement pump as the
main type of pump on a modern fire apparatus.
What has not changed is the necessity to
understand master modern day fire pumps
apparatus.
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Types of Pumps used in the Fire Service

• Positive displacement pumps
• 1. Piston Pump
• 2. Rotary Gear Pump
• 3. Rotary Vane Pump
• Centrifugal pumps -

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• There are various classifications of fire pumps.
• One main classification is according to the
• method of energy that is imparted to the liquid
• Displacement pump - imparts energy by
• mechanical displacement piston, diaphragm,
  plunger, screw, vane gear pumps

• Centrifugal pump - kinetic energy type,
• it imparts energy to a liquid by means of
• centrifugal force produced by a rotating
• impeller

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Positive Displacement Pumps

• Rotary Vane Pump Rotary Gear Pump

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Piston Pumps
1.
3.
4.
2.
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Single / Multi stage centrifugal pumps
Operating principles of single stage pumps

• The single multi stage pumps operate basically
  the same, both use housing encased disks called
  impellers to throw water to the outside of the
  casing to create velocity or pressure.
• The single stage pump has only one impeller to
  discharge water
• The multi stage pump has two impellers that can
  be used in series or parallel operation to
  increase the pressure or to increase the volume
  of water discharged.

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Diagram of how the multi stage pump operates
Pressure Series
Volume Parallel
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Another view of multi stage pump operation
Pressure Series
Volume Parallel
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Major Components of the Centrifugal Pump

• Discharge
• Volute
• Impeller
• Vanes
• Shroud
• Casing
• Stripping edge
• Hub
• Eye

1.
2.
7.
3.
8.
4.
9.
5.
6.
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Centrifugal Fire Pumps
How they work
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How water enters
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Pressure Relief Systems
A pressure relief valve is sensitive to pressure
change its ability to relieve excessive
pressure within the pump discharge. An
adjustable spring-loaded pilot valve actuates
the relief valve to bypass water from the
discharge to the intake chamber of the pump.
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Pressure Control Governors
When activated, the governor Uses trapped air
water in area A as a reference pressure for the
piston that controls the engine throttle. A
change in pump pressure affecting area B moves
the piston adjusting the engine pressure.
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BREAK
BREAK
BREAK
Break
BREAK
BREAK
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Causes of excess pressure in fire hose
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Fire Pump Primers
Successfully drafting water depends upon the
ability to create a partial vacuum within the
pump and intake hose. A positive displacement
pump can pump air as it operates making it self
priming.
Centrifugal pumps are not self-priming
therefore require an external pump to operate
from draft.

• Primers fall into three categories
• Positive displacement pumps
• Exhaust primers
• Vacuum primers

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Positive Displacement PrimersRotary Vane Primer
Require a relatively high RPM as compared to a
rotary gear primer can be driven either
mechanically from the pump gear case, or by an
electrical motor.
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Positive Displacement Primers Rotary Gear Primer
Uses an oil supply to help the pump maintain
effeciency of the pump The oil fills any
irregularities in the housing
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Exhaust Primers

• Operates on the same principle as a foam eductor.
  Exhaust gases are prevented from escaping to the
  atmosphere by the exhaust deflector. Gases are
  diverted to a chamber where the velocity of the
  gases passing through a venturi creates a vacuum

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Vacuum Primers

• Simplest of all primers, it makes use of the
  vacuum already present in the intake manifold of
  any gasoline engine.

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180-1.11
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Conditions that can cause damage to the pump

• Cavitation a condition in which vacuum pockets
  form in a pump cause vibrations, loss of
  efficiency, possible damage
• Water Hammer -- the force created by the sudden
  acceleration/deceleration of water

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Corrective measures to prevent damage to the pump

• To prevent cavitation the engineer must not
  discharge more water than the supply can furnish.
• To prevent water hammer, all discharges must be
  opened/shut slowly.

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Auxiliary Cooling Systems
The primary function of auxiliary coolers is to
control the temperature in the apparatus
engine during pumping operations.
Two types of auxiliary coolers
2. Immersion type

• Marine type

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Descriptions
Marine type inserted in one of the hoses used
in the engine cooling
system is such a way that
the engine coolant must travel through
it as it circulates through the
system the cooler
itself contains a number of
small tubes similar to the flues in a
steam boiler.
Immersion type - the engine coolant passes
through the body
of the cooler, water being
supplied by the fire pump passes
through a coil or tubing
mounted inside the
cooler so that it is immersed in
the coolant
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Intake/Suction Hose Characteristic
Soft suction hose is used to transfer water from
a pressurized source hydrant to the pump
intake Range in size from 2 ½ to 6, can be
constructed of the same material as smaller fire
hose
Hard suction hose is used to draft water from an
open water source. Also used to siphon water
from one portable tank to another, usually in
tanker shuttle operations. Range is size from 2
½ to 6, constructed of a rubberized reinforced
material designed to withstand the partial
vacuum conditions created when drafting
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Nozzle types
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Open bore
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Fog Nozzles
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Broken Stream
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Ball Valves
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Slide Valve
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Rotary Control