Combined Fire-fighting/Irrigation Pumping Stations Design and Control Philosophy

Clare Edwards

Thursday 6th September 2007

Introduction

• Fire/Irrigation Pumping Stations

• Fire/Potable Water Pumping Stations

– What we’re given

– What we produce

– Pumping station

– Standards

– Control Philosophy

– Problems encountered

– Summary

Potable/Firefighting - GM University

Irrigation/Firefighting - UAQ Marina

Information We’re Given

• Users

• Flow

• Pressure at point of discharge

• Network – distances

• Location – sometimes not always known e.g. Lusail

Water Users & Pressure Required

Potable Water Supply

• Potable only

• ~ 4 bar (58 psi)

Fire Fighting

• Potable or treated effluent

• ~ 7 bar (102 psi)

Irrigation

• Treated effluent

• ~ 4 bar (58 psi)

District Cooling

• Treated effluent

• ~ 4 bar (58 psi)

What we Produce

• M&E specifications – specifying equipment, pumps, mechanical

equipment– a standard document that is changed edited for

the purposes of the project– includes pump curves, datasheets, panel

dimensions, etc

• Calculations – Size of pipes, headloss calculations, motor sizing,

thrust on pipe calculations, power load, any further calculations required

• Drawings – P&ID, SLD, GA showing pipe layout, sections,

pipe schedules, roof/access layout

• Control Philosophy – how we propose to operate & control the system

Calculations

• Pipe sizing– Q = vA

• Headloss Calculations – Colebrook-White formula

• Motor Sizing Calculation– P = gHQ /

Example

• Q = 620 l/s

• HT = 80m

• Combined Fire/Irrigation

• Pressure at hydrant

• Maintain 2 hours storage for fire event

Pipe Size & Headloss Calculation

• E.g. Irrigation pump, velocity in pipe<2m/s

• No of pumps required– D/A/A/S => Duty, Q = 207l/s (620/3)

• Try Dia = 400mm

• => A = 0.4²/4 = 0.12m²

• V = Q/A => 0.207/0.12 = 1.65m/s

Pipe Velocities

• 350 dia => 2.15m/s

• 400 dia => 1.65m/s

• 500 dia => 1.05m/s

• 600 dia => 0.73m/s

Headloss Calculation

• Use Colebrook-White to calculate headloss in pipe– Length & diameter of pipe– Flow => velocity– Fittings

• HL= kV²/2g

• HF =

• HT =

Motor Sizing Calculation

• P = gHQ /• P = (1000kg/m² x 9.81m/s² x 80m x0.207m³/s)/ 0.8• P = 203kW + 10% design headroom

• kW => type of starter

• DEWA recommendations– 0-11kW DOL– 15-22kW Star-Delta– 30+ kW Soft Start

Pumps

• Electric Pump with diesel backup/diesel generator backup

• Irrigation Pump/s with jockey pump/s

• Centrifugal pumps (split casing type)

• Vertical multistage

Pump Selection

General Arrangement – Pipe Layout

Process & Instrumentation Diagram P&ID

P&ID (cont)

Single Line Diagram

Main Components

• - storage tank/reservoir – level sensors

• - pump room

• - FEP, FDP, Irrigation pumps, (Potable pumps), jockey pumps

• - valves – flow control and isolation

• - flow meter – to test pump flow rates

• - surge vessel – maintain system pressure

• - (strainers)

• - lifting equipment – overhead bi-directional crane

• - generator, MCC, transformer, mess rooms/building

• - fuel tank

• - standby generator

• - AC and ventilation

Standards – NFPA20

• NFPA 20

– National Fire Protection Association's (NFPA)

– American standard adopted in the UAE

– NFPA 20 Standard for the Installation of Stationary Fire Pumps for Fire Protection

• Key points:– Pumps limited to capacity < 1892 l/min

– PRV

Standards – FM/UL Approved

• FM - Factory Mutual • UL – Underwriters Laboratory

Control Philosophy

• Instruction on how pumping station will operate

– state set points;

– pressure pumps are to maintain the system at;

– how the pumps will operate, e.g. D/A/A/S

– what controls are needed

• Control Philosophy and P&ID is then given to the electrical engineer to complete the SLD, panel layout, and work out electrical loads and power required, size standby generators, etc

• Control Philosophy to be read in conjunction with P&ID

Control Philosophy Assumptions

• Irrigation pumps to operate on demand,

• Jockey pumps to maintain system pressure

• Irrigation networks under central control

• Each branch of network can be isolated (normal condition) or opened when irrigation is required.

• Valves centrally controlled

• Irrigation system controlled by a 24 hour timer

• A PRV to protect pumps and pipework against over pressure.

• Back up diesel generator – for mains power failure

• Sufficient fire-fighting water must be available at all times Hard-wired level sensor in tank to inhibit irrigation pumps

• Flow control valve provided on inlet to storage tank/reservoir.

Actions in event of fire

Fire hydrant opened

Fire pumps start Irrigation & district cooling offtakes close

Detect that fire hydrant has been opened

Variations

• GM University

GM University – Potable/Firefighting

Problems

• Strainers on suction pipework

• D/S strainers requested when the tank and pumping station

• Determining what Civil Defence wants?

• Surge vessels

• Pipe thrust block design

• Ensuring pipework is tied down

Summary

• Good examples of design from various projects

• However….

• …we’re constantly working and improving on the design

• The most important thing is determining what the civil defence requirements are and confirming the design criteria as early as possible

Pump Room Overview

Electric Fire Pump

Diesel Fire Pump

Pressure Relief Valve

Flowmeter

Autostrainers

IMPZ, Dubai

Valve Arrangement

Surge Tank

Monorail Crane

Tied Pipework