Service Delivery 3

Pumps

Aims

To provide students information about fire service pumps and their operation

Learning OutcomesAt the end of the session students will be able to:

• Detail the requirements of a fire service pump

• Describe how a centrifugal pump works

• Describe how a peripheral pump works

• Detail the operating principles of an ejector pump

continued…

• Detail the operating principles of priming devices used within the brigade

• Describe the operating principles of pressure and compound gauges

• List the considerations to be taken into account when carrying water

• List the considerations to be taken into account when relaying water.

Types of pumps

NON-POSITIVE - Displace only liquids a

separate primer being

required to remove the air

from the system.

POSITIVE - Displace both liquids and gases

Requirements of a pump

• Self-contained

• Light in weight

• Able to handle large quantities of water

• Able to produce fairly high pressures

• Reliable

• Easy to operate and maintain.

A fire service pump must be;

Non-positive displacement pumps

• Centrifugal pumps

• Peripheral pumps.

Centrifugal pumps

Consist of;

• Spinning part called the impeller

• Casing called the volute.

Water inlet.

voluteimpeller

Purpose of the volute

• To channel water from the periphery to the outlet

• Reduce water velocity and turbulence

• Increase the water pressure.

water inlet

Guide vanes.

impeller volute

Characteristics of centrifugal pumps

• At any given speed where there is no flow pressure is at a maximum

• Pressure decreases as the delivery valves are opened and the flow increases

• When pump speed increases pressure and flow increase

• When suction lift increases pressure and flow decrease.

Advantages of centrifugal pumps

• Simple maintenance

• Can be run against closed deliveries without damage

• Light and compact relative to their output

• Can be driven directly from an internal combustion engine.

Velocity and pressure changes within a centrifugal pump.

velocitypressure

Suction hose

impellervolute

Increasing pump pressures

This can be done in a number of ways;

• Increasing the size of the impeller

• Increasing the speed of the impeller

• Increasing the number of impellers (as in a 2-stage or multi-stage pump)

• Using a peripheral pump.

Peripheral pump.

Operating principles.

The peripheral pumpAdvantages;• Can produce high pressures at relatively

low running speeds,saving on wear & tear

• Can be mounted on the same shaft as the centrifugal pump

• Ideally suited for use with high pressure hose reels.

The Godiva UMPX pump.

Power take off (PTO)

Directs engine power away from the road wheels to drive another piece of equipment, such as the fire pump.

Cooling systems

• During pumping operations some water is taken from the high pressure side of the pump to a heat exchanger where it assists in cooling the engine

• The water then flows back to the low pressure side of the pump.

Priming

There are three ways to prime a centrifugal pump;

• Use of a gravity fed supply

• Via a pressure fed supply

• By using a priming device to remove air from the pump.

Function of a primer

• Used where a static water supply is lower than the pump

• The primer removes air from the pump and creates a partial vacuum allowing atmospheric pressure to effectively force water up the hard suction into the pump.

Water ring primer.

Rotating impeller

Outlets

Inlet from pump

Water ring primer.

Ring of water Oval

housing

Low pressure

Water ring primer.

Air is forced out of the primer

Air rushes in from pump

Operating principle of the ejector pump.

JetThroatFluid & propellant

Venturi effect

Surrounding fluid

Hughes-Noble ejector pump.

propellantthroat area

Lightweight pump.

Exhaust gas ejector.

Exhaust gas ejector.

Gauges

• Pressure gauge

• Compound gauge

• Tachometer

• Water tank contents

• Oil pressure gauge

• Fuel tank contents

• Engine coolant temperature.

Typical gauge group.

Pressure gauges

• Low pressure gauge

• High pressure gauge.

Showing the output pressure of the pump;

Bourdon tube gauges.

Compound gauges

• Show the inlet pressure of the pump

• The reading may be positive if supplied from a hydrant or negative when lifting from open water.

Compound gauges.

Compound gauge.

Brass housings.

Rear Housing Front Housing

Rear Housing Front Housing.

Vacuum.

Positive Pressure.

Compound gauge.

Negative readings

• A negative reading of 0.1bar would indicate a lift from open water of approximately 1metres

• A reading of 0.4bar would indicate a lift of 3 metres allowing for practical considerations.

Water carrying

• Used where the water requirement is relatively limited

• When the distances between the water source and fireground may be considerable.

Water relaying.

Distances between pumps Depends on;

• The flow required

• Pump pressure used

• Contours of the relay route

• Size, type and number of hose lines

• If the pump is lifting water as well as delivering.

ConfirmationAssessments will be based on this lesson andthe corresponding study note

Learning Outcomes• Detail the requirements of a fire service

pump

• Describe how a centrifugal pump works

• Describe how a peripheral pump works

• Detail the operating principles of an ejector pump

continued…

• Detail the operating principles of priming devices used within the brigade

• Describe the operating principles of pressure and compound gauges

• List the considerations to be taken into account when carrying water

• List the considerations to be taken into account when relaying water.

THE END