CVFD Training – Pump Operations SFFMA Training Objectives 24-01.01 – 24-01.02
NET ENGINE PRESSURE • Net Pump Discharge Pressure (new term) • Actual amount of pressure being produced by the pump. • When taking water from a hydrant, it is the difference between the intake pressure and the discharge pressure. • When drafting it is the total of the intake pressure and the discharge pressure.
NOZZLE REACTION • Counterforce directed against a person holding a nozzle or a device holding a nozzle by the velocity of water being discharged. • Measured in pounds • Nozzle reaction formulas NR= 1.57·d²·NP and NR= 0.0505·Q·NP
POUNDS PER SQUARE INCH(PSI) • U.S. unit for measuring pressure. • Reflected on the discharge gauge • Called Pump Discharge Pressure or Engine Pressure
PUMP DISCHARGE PRESSURE • ENGINE PRESSURE • Actual velocity pressure (measured in PSI) of the water as it leaves the pump and enters the hoseline.
VELOCITY • Speed; the rate of motion in a given direction. It is measured in feet per second for the fire service.
Water Hammer Water moving through a pipe or hose has both weight and velocity. The weight of water increases as the pipe or hose size increases. Suddenly stopping water moving through a hose or pipe results in an energy surge being transmitted in the opposite direction, often at many times the original pressure. This surge is called Water Hammer
WATER HAMMER • Force created by the rapid acceleration or deceleration of water. It generally results from closing a valve or nozzle too quickly. • Can be up to seven (7) times the original pressure.
GAUGES • Master Intake gauge (Compound) • Master Discharge gauge • Discharge gauge (individual gauges) • Oil Pressure • Voltmeter • Tachometer (engine RPM) • Pump overheat indicator • Engine coolant temperature gauge
Master Intake Gauge • Measures positive or negative pressure • Calibrated from 0 to 600 PSI (usually) for positive and from 0 to 30 inches of vacuum for negative pressure • Provides indication of residual pressure from a hydrant or relay operation • Provides indication of maximum capacity of pump when at draft
Master Discharge Gauge • Measures positive pressure • Calibrated from 0 to 600 PSI • Up to 1000 PSI on special pumpers • Measures pressure as it leaves the pump and before it gets to the individual gauges • Always reads the highest pressure the pump is producing
Discharge Gauge • Individual gauges measure the pressure for each individual discharge. • Use these gauges not the master discharge gauge when flowing any line.
Oil Pressure Gauge • Measures oil pressure of the motor. • Normal operating pressures vary with different brands of apparatus. • Variations from normal may indicate pending problems.
Voltmeter • Provides a relative indication of battery condition and alternator output by measuring the drop in voltage as some of the more demanding electrical accessories are used. • Indicates the top voltage available when the battery is fully charged. • Measures drop when electrical demand is high.
Tachometer • Records the engine speed in revolutions per minute (rpm) • It can give valuable information about the condition of the pump. • May refer to the acceptance test rating panel to check on pump efficiency (identification plate on the pump panel)
Pump Overheat Indicator • Audible or visual indicator • * Overheating occurs when the pump impeller is spinning, for prolonged periods, but no water is being discharged
Pump Overheat • Best place to check for overheat is right here • Best way to never overheat the pump is to always be moving water.
Engine Coolant • Engine coolant temperature gauge • Shows the temperature of the engine coolant - the normal operating range of the Detroit Diesel Series 60 Engine is between 192° - 205° Fahrenheit • Caution: An engine that operates too cool is not efficient. An engine that has an operating temperature that is too high may be damaged.
TYPES OF FIRE PUMPS • Piston • Single, Multiple • Rotary • Gear • Centrifugal • Single-stage, Two-stage, Multiple-stage
Pump Equipment • Centrifugal Pump • Multi-stage Pumps • Cavitation • Pressure Relief Valves/Governors • Positive Displacement Primers • Manual Pump Shift • Gauges • Auxiliary Cooler • Valves
Centrifugal Pump • Components • Impeller • Eye • Hub • Vanes • Volute • Shroud • Casing
Pump Impeller Vane Impeller eye Shaft opening Shroud
Centrifugal Pump • Rated at draft • Can double its’ capacity with adequate positive pressure • Non-positive displacement pump • Not self priming • Cavitation occurs when RPM without corresponding increase in pressure
Centrifugal Pump • Three factors influence pump discharge pressure (PDP): • 1) Incoming Pressure • 2) Speed of the impeller • 3) Amount of water being discharged • Single or Multi-Stage • Maximum Discharge Pressure @ 150 psi plus static pressure on hydrant
Rated Capacity • A pump is rated @ draft, the following show the capacity @ different pressures: • 100% @ 150 psi (net pump pressure) • 70% @ 200 psi (net pump pressure) • 50% @ 250 psi (net pump pressure)
Rated Capacity • When connected to a positive pressure source, the capacity of a pump can be doubled (assuming that the source is of adequate size and pressure). • The capacity of a pump can also be increased when using multiple intakes or increasing the size of the supply line.
Two-Stage Centrifugal Pumps • Single vs. Multi-Stage • Pressure (series) vs. Volume (parallel) • Most operations in pressure mode • 50 % rule • Change over @ 50 psi net pump pressure • Transfer valve found on pump panel, usually with indicator light
Two-Stage Centrifugal Pumps • The two-stage pump has two impellers mounted within a single housing. • Generally, the two impellers are identical and have the same capacity. • What gives the two-stage pump its versatility and efficiency is its capability of connecting these two stages in series for maximum pressure or in parallel for maximum volume by use of a transfer valve.
Two-stage Centrifugal pump • Pumping in the Volume (Parallel) Position • When the pump is in the volume position, each of the impellers takes water from a source and delivers it to the discharge.
Pumping in the Pressure (Series) Position • When the transfer valve is in the pressure position, all the water from the intake manifold is directed into the eye of the first impeller. • The first stage increases the pressure and discharges 50 to 70 percent of the volume through the transfer valve and into the eye of the second impeller. • The second impeller increases the pressure and delivers the water (at the higher pressure) into the pump discharge port.
Two-Stage Centrifugal Pumps • Each fire pump manufacturer has recommendations for when the transfer valve on their pump should be in the volume or pressure position. • The process of switching between pressure and volume is sometimes referred to as changeover.
Pump packing • Number of drops from packing. • Water should drip, not run from packing gland • New “Ceramic” packing • Must have temperature relief valve to protect ceramic disk
Cavitation What is Cavitation?
Cavitation • Firefighters definition: • Water is discharged from the pump faster than it is coming in. • Cavitation: • A condition in which vacuum pockets form in the pump and causes vibrations, loss of efficiency, and possible damage.
Cavitation • During Cavitation: • The pressure at the eye of the impeller falls below normal atmospheric pressure. • The water boils faster at temperatures less than normal atmospheric pressure. • Steam and air bubbles are created. • The air bubbles move outward in the impeller and into the high-pressure zone. • The air bubbles collapse, producing noise and vibration.
Cavitation • To Avoid Cavitation: • Intake pressure from pressurized sources should not drop below 20 psi. • Cavitation can be recognized by the fact that increasing the engine rpm does not result in an increase in discharge pressure.
TRANSFER VALVE • Only on Pressure/Volume Pumpers • Switched by: Electric switch, Pneumatic shift, Water-hydraulic, or Manual hand-wheel • Changes pump from Pressure (Series) – to Volume (Parallel) • Switched when pumping greater than 50% of the rated capacity of the pump
TRANSFER VALVE • This is an electric transfer switch • Other switches can be: • Pneumatic • Hydraulic • Manual
TRANSFER VALVE • This is a manual back-up to the transfer switch
POWER TRANSFER • Engine to wheels • Engine to fire pump
Pump drives • Mid-ship mount • Front mount • PTO • Rear mount • flywheel
Mid-Ship Mount • Mid-Ship mount: a split-shaft gear case located in the drive line between the transmission and the rear axle. • Unit will pump or drive, not both.
Power Take-Off • Power is taken off the transmission before it gets to the back wheels for “pump and roll” operation. • The PTO unit is powered by an idler gear in the truck transmission.