Knowledge Objectives(1 of 2) • Explain the importance of understanding the fire pump and its systems. • Describe the exterior and interior features of a pumper. • Define the term pump. • Explain the basic operations of positive-displacement pumps and centrifugal pumps.
Knowledge Objectives(2 of 2) • Explain the different types of positive-displacement pumps. • Explain the different types of centrifugal pumps. • Describe a single-stage pump and a two-stage pump.
Introduction • Without pumps, fire fighters cannot discharge water under pressure to extinguish fire. • The driver/operator of the pump apparatus must understand how pumps operate to be able to fix problems that may arise. • Do not memorize a sequence of tasks; the driver/operator should have a thorough understanding of how the pump operates.
Exterior of the Pumper(1 of 4) • The pumper is a very basic fire apparatus. • Large fire pump with hose and tools to extinguish fires • Most common fire apparatus • Cab sits on a steel frame. • Attached to the frame are storage compartments and the fire pump. • Ground ladders are mounted on the side or stored inside the compartment at the rear.
Exterior of the Pumper(2 of 4) • Supply hose and attack lines are stored in the hose bed. • May be uncovered or covered with a tarp for protection • Most pumpers carry preconnected attack lines for quick deployment.
Exterior of the Pumper(3 of 4) • The pump panel is the most notable device on the apparatus. • May seem confusing until the driver/operator learns the basics of pump operations • Covered in stainless steel and has multiple levers and gauges
Exterior of the Pumper(4 of 4) Courtesy of Jim Hylton Courtesy of Jim Hylton
Interior of the Pumper: The Cab • Inside the cab are all the controls to operate the apparatus. • Interior controls on the engine apparatus are very similar to those on other large vehicles with few exceptions. • Controls to engage the fire pump or to operate emergency lights • Fire apparatus is not like any other vehicle and should not be operated like other vehicles
Pumps(1 of 3) • Fires are extinguished when the proper amount of water (GPM rate) is applied. • Water is directed through a nozzle at the required pressure to give the water stream enough reach to penetrate to the seat of the fire. • Pump pressurizes the water used to attack a fire • The fire pump is defined as a provider of liquid flow and pressure dedicated to fire protection.
Pumps(2 of 3) • Pumps alone do not create pressure. • Pumps displace fluid, which causes fluid to move or flow. • Resistance to flow creates pressure. • Higher pressure means less volume or flow. • Higher flow means less pressure. • Pumps cannot provide a high pressure and a high volume at the same time.
Pumps(3 of 3) • Two sides to all pumps • Intake side is where the water enters the pump. • Referred to as the “supply side” since it is where the water is supplied to the pump • Discharge side is where the water exits the pump.
Types of Fire Pumps • Fire service uses two types of pumps: positive-displacement pumps and centrifugal pumps. • Each relies on different operating principles. • Each offers different features.
Positive-Displacement Pumps(1 of 9) • NFPA 20: A positive-displacement pump produces flow by capturing a specific volume of fluid per pump revolution and reducing the fluid void mechanically to displace a pumping fluid. • Positive-displacement pumps rely on tightly fitting parts to function properly. • Ideal for use as a priming pump for centrifugal pumps
Positive-Displacement Pumps(2 of 9) • Can be used as high-pressure auxiliary pumps or portable pumps • Efficiency depends on the close-fitting moving parts. • Performance will deteriorate with wear and excessive use. • Two classifications • Rotary pumps exhibit a circular motion. • Piston pump have an up-and-down motion.
Positive-Displacement Pumps(3 of 9) • Piston pumps • Use a cylinder to contain the fluid • Draws water from the intake side and pumps it out the discharge side • Three moving parts: piston, intake valve, and discharge valve • Two types of piston pumps: single-acting and double-acting
Positive-Displacement Pumps(4 of 9) • Single-acting piston pump • Operation is very simple. • Similar to a squirt gun • Every pump on the lever discharges fluid from a single-acting piston pump. • Water is discharged only on a downward movement, creating a pulsating effect. • Single-acting piston pumps are not suitable for use on an attack line.
Positive-Displacement Pumps(5 of 9) Adapted from Hale Products, Inc.
Positive-Displacement Pumps(6 of 9) Adapted from Hale Products, Inc.
Positive-Displacement Pumps(7 of 9) • Double-acting piston pump • Lets water flow more continuously using one piston • Still has periods of limited flow • Both valves at each end
Positive-Displacement Pumps(8 of 9) • Rotary pumps are typically used as the priming pump for a centrifugal pump. • Discharge a constant flow of water with each revolution • Rotary gear pump is typically used as a priming pump. • Driven by a 12-volt electric motor
Positive-Displacement Pumps(9 of 9) • Rotary vane pump uses small moveable vanes to freely move in and out of rotor slots to maintain a tight seal against the pump casing. • Vanes automatically maneuver in and out to compensate for changes in the pump casing. • Centrifugal force keeps the vane tightly pressed against the pump casing, ensuring a tight seal.
Centrifugal Pump(1 of 11) • Most common fire pump used today • Replaced positive-displacement pumps on modern fire apparatus • Water flow discharge is based on pressures at the discharge side of the pump. • At higher flow rates, the pump flows less volume but creates higher pressures.
Centrifugal Pump(2 of 11) Adapted from Hale Products, Inc.
Centrifugal Pump(3 of 11) • Driver/operator needs to understand how the pump works to maximize its potential in firefighting operations. • Pump operates on a principle of centrifugal force: the outward force from the center of rotation • The pump receives water into the center or eye of the impeller mounted inside the pump casing. • Impeller transfers energy from the vehicle’s motor to discharge incoming water
Centrifugal Pump(4 of 11) • Centrifugal pump can pump only water or other liquids. • No valves from intake to discharge side • Not self-priming • Takes advantage of incoming pressure on the intake side to increase the discharge pressure • Single-stage (one impeller) or multistage (two or more impellers within one pump housing turning on the same shaft)
Centrifugal Pump(5 of 11) • A single-stage pump has one impeller that takes in and discharges water out of the pump. • A single impeller supplies 100 percent of the total water. • Simple to operate
Centrifugal Pump(6 of 11) Adapted from Hale Products, Inc.
Centrifugal Pump(7 of 11) • Two-stage pump is the most common multistage pump • Two impellers enclosed in the pump casings • Each impeller is identical in size and capacity. • Transfer valve determines whether the pump will be operated in a series/pressure mode or parallel/volume mode
Centrifugal Pump(8 of 11) • Parallel/volume mode: • Water enters each impeller and is discharged into a common discharge header. • Use when more than 50 percent of pump’s rated capacity needed • Series/pressure mode: • Water travels through one impeller in the series. • Most common operating position for two-stage pumps Adapted from Hale Products, Inc. Adapted from Hale Products, Inc.
Centrifugal Pump(9 of 11) • Fire pump is rated by and tested to UL specs • Pump must produce: • 100% of rated capability at 150 psi (1034 kPa) for 20 minutes • 70% of rated capability at 200 psi (1400 kPa) for 10 minutes • 50% of rated capability at 250 psi (1723 kPa) for 10 minutes • No rating provided for pressures over 250 psi
Centrifugal Pump(10 of 11) • Control valve on the pump panel of a multistage pump indicates whether impellers are operating in a parallel/volume or series/pressure mode • Two-stage pump is similar to working from a hydrant water supply and pumper
Centrifugal Pump(11 of 11) • Special multistage pumps are built to produce high pressures for special pumping requirements. • Pump capacity has increased significantly with the development of larger pumps with larger impellers. • 1950s: pumps delivered flows of 500 or 700 GPM (1892 or 2839 L/min) • Today: pumps can flow at 2000+ GPM (7570+ L/min)
Power Supplies for Pumps(1 of 5) • Driver/operator must know how pumps receive power. • Study schematics and manuals. • Simplest form of power supply is available with the portable pump. • The pump is carried by two or more fire fighters to the water source. • Some apparatus have a pump mounted on the front bumper.
Power Supplies for Pumps(2 of 5) Courtesy of Har-Rob Fire Apparatus, Inc.
Power Supplies for Pumps(3 of 5) • Power take-off (PTO) units are used for small pumps like on tankers or tenders. • Provides a less-expensive method of developing pump power • Provide a pump-and-roll capability for certain apparatus • A transfer case is the most common power system found in pumps. • Gearbox is mounted between transmission and rear axle
Power Supplies for Pumps(4 of 5) Adapted from Hale Products, Inc.
Power Supplies for Pumps(5 of 5) • Pump speed is directly related to transmission speed • Transmission in first gear propels the pump at a slow pace. • Transmission in fifth gear turns it much faster. • Automatic transmissions are made for pumping operations that will lock into the intended gear once the apparatus is in pumping mode.
Summary(1 of 2) • The stainless steel pump panel is the most notable device on the apparatus. • A driver/operator who understands the pump and its functions can operate with confidence. • A pump is a mechanical device to move fluids; fire fighters want the pump to move water from a source to the fire through attack lines.
Summary(2 of 2) • Fire service uses two types of pumps: positive-displacement pumps and centrifugal pumps. • At higher flow rates (rpm) the pump flows less volume but creates higher pressures.