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Fire Apparatus Pump Theory

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Presentation on theme: "Fire Apparatus Pump Theory"— Presentation transcript:

1 Fire Apparatus Pump Theory
Section 180

2 Introduction Types of pressure encountered in the fire service
Identify the types of fire pumps & components of pumps Identify the function, theory, principles of operation of fire pumps All of these terms are defined in the NFPA 1002 (1998 Edition) paragraph 3-2.1b

3 Types of pressures encountered in the fire service
Static pressure Residual pressure Flow pressure Normal operating pressure Negative pressure

4 Static pressure The pressure exerted in all directions
at a point in a fluid at rest Static pressure is stored potential energy that is available to force water through a pipe, fittings, fire hose & adapters Water at rest can be defined as water that is in a standing state & in undergoing no physical change. H2o is incompressible It takes 33,000psi to reduce its volume by 1% a

5 Residual pressure The pressure remaining in a system while water is flowing The total available pressure not used to overcome friction or gravity while forcing water through pipes, fittings, fire hose & adapter During a flow test of a hydrant the term residual represents the pressure left in a distribution systems within vicinity of one or more flowing hydrants Affected by a number of factors: Water flowing from 1 or more hydrants Consumption demands The size of the pipe Something important to remember is that residual pressure MUST be identified at the location where the reading is taken c

6 Flow pressure The forward velocity pressure at a discharge opening when water is flowing The rate of flow {velocity} of the water coming from the discharge opening produces this force called velocity or flow pressure Forward velocity can be measured by using a pitot tube & gauge as flow pressure If the size of the opening is known, the flow pressure can be used to calculate the quantity of water flowing in GPM An example of flow pressure is one in which the forward velocity of a water stream exerts a pressure that can be read on a gauge d

7 Examples of how static, residual & Flow pressures are measured
Water pressure

8 Normal operating pressure
The pressure found in the water distribution system during normal consumption demands Occurs when some water is flowing in the system When water starts moving in the system static pressure no longer exists The difference in static & NOP is the friction loss caused by the water flowing through various fitting, pipe, valves in the system The demands for water consumption continuously fluctuates during the day & nite & the flow of water will therefore increase or decrease the amount of pressure available in the system b

9 Grid system

10 Negative pressure Also called vacuum . Pressure that is less than atmospheric pressure Negative pressure in the fire service is the result of drafting operations, which results from removing all the air from the pump & using atmospheric pressure to lift water from a source lower than the pump negative pressure is anything less than 14.7 which is atmospheric pressure at sea level Drafting is the process of drawing water from a static source into a pump that is above the level of the water supply Any pressure less than atmospheric pressure is called a vacuum Negative pressure can also occur when the pumper tries to acquire more water from the distribution system that the system can supply e

11 Terms related to the basic principles of fire service hydraulics
Atmospheric pressure – the atmosphere that surrounds the earth has depth & density & exerts pressure upon everything on earth The atmospheric pressure is greatest at low altitudes & sea level pressure is used as the standard psi / 100 kPa a common way of measuring AP is to compare the wt of the atmosphere w/ the wt of a column of mercury, the greater the pressure the taller the column of mercury The pressure of 1 psi /7 kPa will make the column of mercury about 2.04” / 52mm tall, The readings on pressure guages are psi in addition to the existing atmospheric pressure of a gauge reading 10 psi at sea level is actually indicating 24.7 psi 2. Pump capacity is determined by the amount of water the pump can move at a given pressure. recognized capacities for fire pumps are 500, 750, 1000, 1250, 1500, 1750, 2000 gpm but some larger capacity pumps are used in industrial applications Pumpers must have adequate intake & discharge pump connections, pump & engine controls, guages, & other instruments Capacity – The maximum amount of water a pump will deliver at the indicated pressure

12 Displacement – Movement of a given amount
of a fluid w/ each stoke of a pump Flow {GPM} – Gallons per minute, the measurement of the amount of water moved through a fire pump Friction loss – Loss of pressure created by the turbulence of water moving against the interior walls of the hose or pipe.

13 Friction loss ex 1

14 Friction loss ex 2

15 Head Pressure (gain of loss) – Water pressure
due to elevation. For every 1’ increase in elevation, psi is gained. 1 M in height 10 kPa is gained Hydrant pressure – The force of water when it enters the pump from the distribution system Head in the fire service refers to the height of water above the discharge orifice to convert head in feet to head in pressure divide the number of feet by which is the number of feet that 1 psi will raise a column of water Hydrant pressure will decrease as the discharge increases, this is due to friction loss in the after system. It the flow is increased too much, the pressure in the system may be reduced below 0 psi. Operation at negative pressure is dangerous because it increses the possibility of damage to the system due to a water hammer if the flow is shut off suddenly NPDP When taking water from a hydrant it is the difference between the intake pressure & the discharge pressure when drafting it is the sum of the intake pressure & discharge pressure NOTE intake pressure is credited for lift & intake hose friction loss & is added to the discharge pressure Net engine pressure – The actual amount of pressure being produced by the pump

16 Nozzle reaction – The counterforce directed
against the people or device holding a nozzle by the velocity of water being discharged Pound per square inch PSI - Pump discharge pressure – The actual velocity pressure (measured in PSI) if the water as it leaves the pump & enters the hose line.

17 Vacuum – A pressure that is less than normal atmospheric pressure
Velocity – The rate of motion of a particle in a given direction, speed Water hammer – When the flow of water is suddenly stopped, the resulting surge is referred to as a water hammer A water hammer is often be heard as a distinct sharp click, very much like a hammer striking a pipe. This sudden stopping results in a change in the direction of energy. This energy creates excessive pressures that can cause considerable damage to water mains, plumbing, fire hoses, hydrants, & fire pumps. Always operate nozzle controls, hydrants valves & hose clamps slowly to prevent a water hammer

18 Water hammer

19 Break Time!! Thank Goodness Break

20 The firefighter shall identify & describe the following guages:
Compound gauge – A gauge connected to the intake side of the pump that is capable of measuring positive & negative intake pressures Discharge/pressure gauge – A gauge on the discharge side of the pump that registers the pump discharge pressure


22 Suction Pressure Usually the largest two gagues on the panel
these are located at the top of the panel Suction Pressure

23 Pressure loss

24 Flow chart


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