INDUSTRY GUIDE

HYDRO-ELECTRIC POWER

GENERATION

VESDA

VESDAVESDA

VESDA

®

ASPIRATING SMOKE DETECTION

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VESDA

VESDAVESDA

VESDA

®

Hydro-Electric Power Generation

Feburary, 2002

DESIGN GUIDE

© Vision Fire & Security.  All Rights Reserved.

DISCLAIMER

This publication is a guide only.  Reference to local codes and standards for compliance of system design should always be sought.  No part of this document may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying and recording, for any purpose without the express written permission of Vision Systems.  For more information, please contact your nearest Vision Fire & Security office.

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VESDA

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Hydro-Electric Power Generation

Feburary, 2002

DESIGN GUIDE

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CONTENTS

INTRODUCTION............................................................................................................4

PRIMARY CONSIDERATIONS ..................................................................................... 4

OPERATING AREAS OF A HYDRO-ELECTRIC POWER PLANT..............................4

DESIGNING A SYSTEM ACCORDING TO STANDARDS........................................... 6

PERFORMANCE BASED DESIGN............................................................................... 6

CHALLENGES TO SMOKE DETECTION .................................................................... 6

PIPE DESIGN FOR SMOKE DETECTION.................................................................... 7

STANDARD ROOM SAMPLING...................................................................................7

INTERBEAM SAMPLING.............................................................................................. 7

STRATIFICATION ......................................................................................................... 8

GENERATOR HALLS ................................................................................................... 9

ARMATURE/COMMUTATOR HOUSING ................................................................... 10

SWITCH ROOMS......................................................................................................... 11

CONTROL ROOMS..................................................................................................... 13

CABINET PROTECTION............................................................................................. 14

CABLE TUNNELS....................................................................................................... 16

CABLE CHAMBERS ................................................................................................... 17

BATTERY ROOMS......................................................................................................18

HIGH/LOW VOLTAGE ANNEXES.............................................................................. 20

GLOSSARY ................................................................................................................. 21

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Hydro-Electric Power Generation

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DESIGN GUIDE

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1. INTRODUCTION

The Power Generation industry uses different types of fuels to generate electricity. The type of power generation plant is classified by the source of fuel, which includes fossil fuels (coal, gas, oil), nuclear and renewable fuels (hydro-electric, wind and geothermal).

Hydro-electric power is considered a clean, renewable source of energy that does not emit pollutants or greenhouse gases into the atmosphere, and has the ability to provide a high instantaneous output. Due to its cost-efficient characteristics and low environmental impact, hydro-electric power is considered a suitable alternative to fossil fuel power generation.

The basic premise of hydro-electric power generation uses running water to generate electricity; water is used to rotate turbines that drive a generator, which then produces electricity.

An early warning smoke detection system not only reduces the risk of fire and prohibitive cost of equipment repairs, but may also prevent the incidence of nuisance alarms, which could result in generation downtime, and loss of revenue.  VESDA can provide reliable warning in a hydro-electric power plant by detecting a fire at the incipient (pre-combustion) stage.

The Industry Guide has been developed by a team of VESDA engineers who have extensive design and installation knowledge in hydro-electric power generation environments.

The content herein is to be used as a reference by designers and consultants when specifying a VESDA system.  It discusses relevant design considerations and recommends the correct method of installing an aspirating smoke detection system in a hydro-electric power plant.

NOTE: This Industry Guide has been produced as a global reference. It should be used in conjunction with regionally specific fire codes and national standards.

2. PRIMARY CONSIDERATIONS

The following design aspects should be considered during the specification of an aspirating smoke detection system:

••

••

Local Fire Codes and Standards;

Power Generation Industry Codes of Practice;

••

••

Key fire risks in different operational areas; Airflow aspects in different operational areas;

••

Manning levels and remote sites, e.g. unmanned remote generation systems.

OPERATING AREAS OF A HYDRO-ELECTRIC POWER PLANT

Hydro-electric power plants contain a diverse range of operating areas that have specific equipment, processes and environmental requirements.  Additionally, each area exhibits a varied degree of fire risk.  It is imperative that the specification of the air sampling system be designed to address the requirements of the operational areas. The following guidelines are to assist consultants and designers achieve the optimum level of detection required within the identified areas. Local standards and codes of practice should always be taken into consideration.

Alarm levels and appropriate levels of response are determined by individual application environments and are not addressed in this Industry Guide.

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VESDA

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Feburary, 2002

DESIGN GUIDE

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Table 1 indicates the operational areas of a hydro-electric power plant in which VESDA can be used.

Areas

Switch/Relay Rooms

Essential

Recommended

Room Sampling

Cabinet Sampling

!

!

Control Rooms

Room Sampling

Cabinet Sampling

Under Floor Sampling

Cabinets

!

!

!

Cabinet Sampling

!

Cable

Tunnels/Chambers

Room Sampling

!

Generator Halls

Room Sampling

Cabinet Sampling

Armature/Commutator

!

!

Housing

Armature Internal

Commutator Internal

!

!

Battery Rooms

Room Sampling

High Voltage Annexe

!

Room Sampling

Cabinet Sampling

!

!

Low Voltage Annexe

Room Sampling

Cabinet Sampling

!

!

Table 1 - Areas of Protection

The following sections describe design recommendations related to the different detection areas. All pipe work designs should be verified using the VESDA Sampling Pipe Modelling Program – ASPIRE™. This program illustrates the significance of various parameters in an aspirating smoke detection system so that the most appropriate design can be applied.

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DESIGNING A SYSTEM ACCORDING TO STANDARDS

The choice and level of protection is dependent on the characteristic risks of the power plant and the requirements of local fire codes and standards.  VESDA’s ability to provide performance-based solutions provides the opportunity to address individual site and equipment specifications.  This is in addition to the normal method of installing the sampling pipework to replace conventional point or beam detectors.

4.1.  PERFORMANCE BASED DESIGN

Performance-based design determines alternate fire protection systems by assessing the sites’ environmental risks at the concept design stage. Traditional prescriptive codes and standards have proven to provide an appropriate level of fire protection with a reasonable safety margin.  However, as tools and industry expertise continues to develop, the fire protection strategy in many installations is being designed from a risk and performance-based design approach.  This may include the use of computerised modelling tools (ie. Computational Fluid Dynamics) and analysis of on-site tests (ie. smoke testing) to determine airflows, fire loading, ventilation, ignition sources and other physical/environmental conditions that may affect the likely development of a fire.

VESDA systems complement performance-based designs by providing an appropriate early warning and response to a hydro-electric power plant compared to conventional detection systems.  VESDA is also easily incorporated into the overall Fire Response Plan, and verification tests can be administered to confirm that the installed system is providing the specified protection.

The following sections address physical conditions and risks of a hydro-electric power plant.

CHALLENGES TO SMOKE DETECTION

The Environment

While a hydro-electric power plant may be considered to be ‘clean’, as opposed to a ‘dirty/dusty’ coal power plant, the site contains a diverse range of operational areas that have specific challenges to smoke detection.  For example, the increased airflow and confined space of the Commutator/Armature Housings or the high volume, open area of Generator Halls may affect the detection capability of conventional smoke detectors.

The size and volume requirement of a Generator Hall exposes the area to the incidence of smoke stratification/thermal layering.  In comparison, the location and size of the Commutator/Armature Housings can affect both the effective detection of smoke and the subsequent response level by conventional smoke detection systems.

Fire Risks

There are several identified fire risks at a hydro-electric site.  The primary consideration is the massive oil reservoirs that are required to operate and lubricate the hydraulic equipment.  Additional risk factors include the high voltage concentration of cable networks, switch gear and control equipment (usually cabinet-enclosed), and banks of high capacity batteries that are used to supply the on-site back-up power systems.

The increased airflows and incidence of smoke stratification in specific areas further expose the site to the threat of fire.

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Typical sources of ignition in a hydro-electric power plant are:

••

••

Under lubricated rotating machinery parts that create friction. Overheated/failed bearings.

••

••

Sparking and static electrical charge.

Overheated electrical control equipment, e.g. switchgear, cables and wires.

••

Lubrication and hydraulic oils reaching their flash point.

PIPE DESIGN FOR SMOKE DETECTION

6.1.  STANDARD ROOM SAMPLING

Standard room sampling is typically installed in a grid format so that each sampling hole corresponds to the location of a point detector (Refer Figure 1 and 2).  Reference should always be made to local fire codes and standards.

Figure 1 - Grid layout

Figure 2 - Standard room sampling layout

6.2. INTERBEAM SAMPLING

Certain operational areas may have support beams and voids as part of the ceiling configuration.  In areas with ceiling voids exceeding 600mm (1.96ft) it may be necessary to sample within the voids for code compliance. This is most easily achieved by incorporating ‘walking stick’ style capillary sampling, rather than using pipe bends.  This method of sampling allows the shortest possible smoke transport time while allowing a longer pipe run than would otherwise be possible. (Refer to Figure 3)

Figure 3 – Walking stick capillary sampling

Void Space

Sampling Hole

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6.3. STRATIFICATION

The occurrence of smoke stratification must be considered when installing sampling pipework. Stratification refers to the incidence of smoke layering that results from heating and cooling of air within an enclosed area, such as Generator Halls.  Factors such as temperature, ventilation and roof height can affect the degree of stratification and level of smoke rise.

To overcome the effect of stratification, it is recommended vertical sampling pipe be installed in addition to standard room sampling.  The vertical sampling pipe allows air to be drawn from multiple heights or layers, and therefore provides earlier detection of smoke.  (Refer to Figure 4)

Figure 4 – Smoke stratification: VESDA multiple level sampling v’s conventional detectors.

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GENERATOR HALLS

Generator Halls are generally large volume areas with roof heights in excess of 10m (32.8ft).  The primary function of the area is to accommodate the sites’ generators and associated cable network, electrical switching and control equipment (typically enclosed within cabinets). The basic premise of the generator is to produce electricity for transmission. An energy source rotates the turbines, which then drive the generator to produce electrical output. Exciter cabinets and the low voltage and high voltage control cabinets assist in the control of this output.

The impact and consequence of a critical loss, and the cost of generator replacement, equipment repairs and revenue loss caused by a fire event make it imperative to install an early warning smoke detection system throughout the Generator Hall.

The combination of high voltages, electrical currents, elevated temperatures and rotating/vibrating machinery increases the possibility of overheating cabling and equipment.  The switching gear and control equipment housed within cabinets (and typically located around the exterior wall of the Generator Hall) requires monitoring for signs of incipient smoke in the event of overheating or sparking.

The stratifying air layers and variable airflows within Generator Halls may create a challenge to conventional smoke detection.  Smoke stratification results from heating and cooling of air within an enclosed area.  The low levels and/or small increases in smouldering smoke become increasingly difficult to detect by ‘passive’ conventional detectors, which only activate an alarm when a significant amount of smoke is generated.

External detection of smoke during the incipient (pre-combustion) stage of an in-cabinet fire may also be affected due to low thermal energy within the cabinets, poor room ventilation, or smoke dilution due to forced air ventilation in cabinets.

It is recommended that room sampling (ceiling and multiple level vertical sampling pipes – Refer to Figure 5), and in-cabinet sampling is installed in Generator Halls.  VESDA’s cumulative early warning smoke detection allows positioning of sampling points at various heights to compensate for stratification; actively sampling the area for smoke.

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Figure 5 – Layout of a typical hydro-electric site

ARMATURE/COMMUTATOR HOUSING

The Armature and Commutator are fundamental parts of the power generation process and are integral to controlling the generation of electricity produced by a hydro-electric power plant.

The primary role of the Commutator is to create electric current to operate the Armature.  In effect, the Exciter/s continue to power the Armature, that then stimulate the generators to produce electricity.  For safety reasons, the Armature and Commutator (and their supporting cables and electric equipment) are enclosed within a metal or concrete Housing.

Due to the operation-critical function of the Commutator and Armature, the consequence from the threat of fire can disable the entire site.  Installing early warning smoke detection in the Commutator and Armature Housing assists in the avoidance of generation downtime, subsequent re-power up and inevitable revenue loss.

The combination of high operational temperatures and concentrated electrical currents inside the Housings increase the risk of overheating and/or electrical failure.

Additionally, access to the Housing interior for the purpose of maintenance operations is limited; creating further difficulty when servicing conventional fire detectors.

When determining the pipework configuration for Armature and Commutator Housing, the area layout and associated machinery placement must be considered.  It is imperative to address both the installation and maintenance of the system in the initial design stage.

Generator Hall

VESDA Detector

Multiple Level Sampling

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A single air sampling pipe is installed around the Armature and/or Commutator that follows the curvature of the Housing.  (Refer to Figure 6) The sampling pipe should be positioned as close as the

possible to

recommended that sampling holes are spaced at 500mm (1.6ft), with a maximum spacing of 1m

Armature/Commutator

(refer

to individual

manufacturer

specification).

It is

(3.28ft).  Care should be taken that the pipework does not develop kinks or cracks while being curved. Pipe clamps can be be placed at specific points to support the curve in the pipework.

VESDA overcomes maintenance and serviceability issues by positioning the detector external to the Commutator/Armature Housing and sampling air from inside the protected environment.  A return air pipe is connnected to the exhaust air port of the VESDA and then returned to the Armature and/or Commutator Housing.

Figure 6 – Sampling pipework installed within the Commutator Housing

9. SWITCH ROOMS

The Switch Room is a dedicated space that accommodates a high concentration of electronic cabinets and automated switchgear.  The in-cabinet equipment maintains the primary functions of the power plant, and is the switching interface between the Control Room and the field equipment.  Additionally, the area accommodates a significant amount of metering and logging equipment.

Although the fire risk may be considered low, it is imperative to install early warning fire detection due to the critical nature of the equipment and demand on the continuous operation of the Switch Room.

There are several challenges to the detection of a Switch Room fire.  The electrical demand of the in- cabinet equipment is a major risk and is the primary cause of a fire incident.

In the occurrence of an in-cabinet fire, the initial low thermal energy inside the cabinet may affect the external detection of smoke during the incipient (pre-combustion) stage.  The poor ventilation of cabinets can also affect the detection of smoke by external devices during the crucial incipient stage.

A further consideration is that the nature of the in-cabinet equipment may require a high level of airflow to maintain a suitable operational temperature.  Forced air ventilation within the cabinet can increase the risk of smoke dilution and therefore limit the ability to detect within the cabinet when using conventional detection systems.

Commutator

Sampling Pipework

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It is recommended that both ceiling mounted and in-cabinet sampling be located in the Switch Room. Cabinet sampling eliminates the risk of delayed smoke detection, which can result from low thermal energy and/or smoke dilution.

Ceiling Mounted:

The positioning of ceiling mounted pipework and sampling holes is dependant on the layout and configuration of the Switch Room.  Reference should be made to local standards regarding the appropriate spacing and density of the sampling holes (detection points).

Cabinet Sampling:

The cabinet configuration is the main consideration when determining the type of pipework sampling method for cabinet protection.  Depending on the cabinet construction, either in-cabinet (fully- enclosed) or above-cabinet (top-vented) sampling is recommended.

Above cabinet sampling is achieved by locating the sampling pipe directly over the ventilation grille of the cabinet.  It is recommended that each cabinet must have a minimum of one dedicated sampling hole that faces the direct airflow out of the cabinet.

cabinet sampling is achieved by installing capillary sampling pipes either through the top of the

cabinet or through the bottom (via the floor void) of the cabinet.

Refer to Section 11: Cabinet Protection for further explanation on the above air sampling methods.

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10. CONTROL ROOMS

The control room is the main command centre of the power plant. The entire site operation is monitored, maintained and adjusted from this central location.  Control rooms are a key consideration due to the high concentration of computers, control equipment, electronic switching devices and underfloor cabling.  While the actual risk of fire is low, the consequential impact of a control room fire necessitates earliest warning.

A control room may range from a small, seldom manned, non-ventilated room, to a massive high-tech air conditioned command and control station with multiple consoles and operators controlling every function of the facility.

Control rooms provide a challenge to traditional detection methodologies due to the fact that most computer and control equipment is housed within cabinets, which can impede the detection of smoke at ceiling level.   The ability of conventional systems to detect a fire can also be affected by smoke dilution caused by the control room’s HVAC system.

VESDA system design provides several methods to overcome the issue of compartmentalised and/or diluted smoke.

Locating sampling pipework at ceiling level, under the floor void and across the return air grille of the air conditioning units provides the earliest possible detection at the incipient stage of a control room fire event.  (Refer to Figure 7)

Figure 7 – Underfloor, ceiling mounted and return air grille sampling.

In addition, the presence of equipment cabinets and consoles may require direct in-cabinet sampling. VESDA’s high sensitivity and cumulative sampling allows very small levels of smoke to be identified at the earliest stage.

Refer to Section 10: Cabinet Protection for further explanation on the above air sampling methods.

Ceiling Mounted Sampling

Return Air Grille Sampling

Underfloor Sampling

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CABINET PROTECTION

Electrical, relay and communication equipment is typically mounted on equipment racks and housed within enclosed cabinets.  These cabinets may be fully enclosed or have a ventilation system.  The ventilation system may either be located as a grille at the top of the cabinet, or as forced ventilation with fans and grilles located at various points within the cabinet.

The equipment or wiring within a cabinet may overheat presenting a fire risk.  Smoke or fire within a cabinet may not be detected outside the cabinet until either a fire is already in progress or significant damage has occurred.  Cabinet protection can be maximised by using a VESDA Laser System designed to detect overheating wiring and equipment in the pre-combustion (incipient) stage of a fire.

In the occurrence of an in-cabinet fire, the low thermal energy inherent in the cabinet may affect the detection and response of an external smoke detector during the incipient (pre-combustion) stage.

In addition, the poor ventilation (convectional cooling only) of cabinets can also affect the external detection of smoke during this crucial incipient stage.

A further consideration is that the nature of the in-cabinet equipment may require a high level of airflow to maintain a suitable operational environment.  The forced air ventilation can increase the risk of dilution and therefore the ability to detect smoke.

The VESDA Laser System can protect in-cabinet equipment by continuously sampling the internal cabinet environment.  This is achieved by In-Cabinet or Above Cabinet Sampling.  (Refer to Figure 8)

In-Cabinet Sampling:

Capillary tubes or drop pipes are inserted into a cabinet from the top or from the under floor void to sample the air within a cabinet.

In-Cabinet Sampling  - Top Mounted:

Sampling pipe is positioned over the cabinet and capillaries or drop pipes are attached to the sampling pipe at appropriate intervals.  It is recommended that, unless specified otherwise, the capillary tube or drop pipe should enter the interior of the cabinet to a depth of 25 - 50mm (1 – 2’).

In-Cabinet Sampling - Floor Void:

Sampling pipe is installed in the under floor void.  Capillary tubes or riser pipes are attached at appropriate intervals.  Holes are then drilled in the floor and the base of the cabinet.  Capillary tubes or riser pipes are run through the bottom of the cabinet to the top, and supported at the cabinet’s roof by a mounting clip.  It is recommended that the sampling hole is faced downwards and, unless specified otherwise, it should be 25 - 50mm (1 – 2”) below the interior of the cabinet top.

Above Cabinet Sampling:

Above cabinet sampling is achieved by locating the sampling pipe directly over the ventilation grille of the cabinet.  Stand-off posts are then used to mount the sampling pipe 25 - 200mm (1 - 8”) above the grille (depending upon air movement). Each cabinet must have at least one dedicated sampling hole that faces the direct airflow out of the cabinet.

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Figure 8 – Capillary and Above Cabinet sampling options

Capillary

Sampling

Above Cabinet

Sampling

Airflow

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12. CABLE TUNNELS

Cable Tunnels are long passageways that accommodate lengths of racking that support the communication and control cabling, and the various power cabling to and from specific operational areas.  The information distributed by the cables is fundamental to the uninterrupted operation of the facility. In a typical layout, numerous lengths of Cable Tunnels link the Control Room, Switch Room and High/Low Voltage Annex areas.

Cable Tunnels generally range in size from 1 - 3m (3 - 9.8ft) in width and 2-3m (6.5 – 9.8ft) in height.

Cable Tunnels are a significant fire risk due to the large and constant amount of power being carried on the cables.  The entire operational function of the power plant is dependent on the uninterrupted transportation of information.

Generally classified as confined spaces and located underground, Cable Tunnels are classified as a typically hostile environment, with an increased level of ambient background pollution. Additionally, the configuration and location of the tunnels not only impede general access, but can also affect the response to, and containment of a fire.

The most efficient way to protect the Cable Tunnel area is to install ceiling mounted pipework with long single pipe runs extending in two directions from a central detector.  (Refer to Figure 9)

Figure 9 - Cable tunnel protected by VESDA detector

VESDA Detector

Bi-directional

sampling pipes

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CABLE CHAMBERS

Cable Chambers are an integral link to the control and coordination of a facility.  The cables located along the Cable Tunnels are grouped together in Cable Chambers for further distribution into various cabinets and control equipment.

Cable Chambers can range in size from 5-30m (16 – 98ft) in width and length and 2-3m (6.5 – 9.8ft) in height.

Cable Chambers are a high fire risk due to the extremely large amount of power that is continuously flowing in the cables.  Although the cables are have minimal voltages with relatively low power, when grouped together and overlaid, the risk of damage increases, particularly during cable mining and replacement operations.

The Cable Chamber area is typically located below ground level and is a confined space with a low rate of airflow.

The most efficient way for a VESDA system to protect Cable Chambers is to install ceiling mounted pipework with multiple pipe runs.  The sampling holes are usually configured in a code-based format. VESDA’s high sensitivity and cumulative sampling allows very small levels of smoke to be identified.

NOTE: Interbeam Sampling

It is common for Cable Chambers to have support beams that support the floor above (usually a Switch Room).  It may be necessary to sample within the voids produced by these beams for code compliance. This is most easily achieved by incorporating ‘walking stick’ style capillary sampling, rather than using pipe bends.  This method of sampling allows the shortest possible smoke transport time while allowing a longer pipe run than would otherwise be possible. (Refer Section 6.2 – Interbeam Sampling)

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14. BATTERY ROOMS

The Battery Room houses lead acid or nickel cadmium batteries that supply the site’s uninterrupted power supply (UPS).  The UPS is used as a back-up power source and to start the facility in the event plant shutdown.   The size and configuration of the Battery Room is dependent on the power required by the UPS to operate the facility.

VESDA’s system design detects the incidence of overheating cells and links, and failures in high current cables and bus bars.

The environment within the Battery Room may become explosive due to the build up of high concentrations of hydrogen gas.

It is recommended that either ceiling mounted and/or Exhaust Air Sampling be installed to protect Battery Room environments.

On Ceiling Sampling:

The pipework is mounted approximately 25 to 100mm (1 to 4”) below the ceiling.  The spacing, diameter of the sampling holes, and the end cap vent size are determined using ASPIRE calculations.

Exhaust Air Sampling:

Exhaust Air Sampling can either be positioned at the exhaust air grille of the duct (Exhaust Air Grille Sampling), or located in the duct (In-Duct Sampling)

Exhaust Air Grille Sampling:

Incipient smoke generally tends to travel with the natural airflow. By positioning pipework with sampling holes across the air grille of an exhaust ventilation system, any smoke generated in the Battery Room is detected at the earliest stage.

(Refer to Figure 10)

Figure 10 – Exhaust Air Grille Sampling

In-Duct Sampling:

    Duct Sampling is achieved by locating a sampling pipe across the entire width of the duct, and along its centre line.  In this particular application, the sampling pipe is commonly referred to as a ‘probe’.  (Refer to Figure 11)

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Figure 11 – In-Duct Sampling

Sampling holes are drilled into the probe and positioned 20 to 45 above or below the centre line of

o

o

the airflow stream.  The sample air is then exhausted from the detector back into the duct. To avoid air disturbances from the inflow of air, the in-take probe should be diagonally offset at least 300mm (1ft).  The exhaust probe is typically inserted to a third of the duct's width.

NOTE: It is important to ensure that the points where the probes enter the duct are properly sealed and made airtight.

Separate detectors are required for in-room and in-duct sampling.

‘Probe’ sampling pipe

NB: Illustration is not to scale

Airflow

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15. HIGH/LOW VOLTAGE ANNEXES

High/Low Voltage Annexes contain the voltage control and transmission equipment, which is necessary for the operation of any facility. These areas typically consist of rows of cabinets which may be either fully enclosed, or have a top mounted ventilation grille.

A failure of the circuitry or wiring within a cabinet may cause it to overheat; presenting as a significant fire risk.  Cabinet detection and protection can be maximised by installing a VESDA detector to detect overheating wiring and equipment in the pre-combustion (incipient) stage of a fire.

The low thermal energy produced by a smouldering cable and/or poor ventilation of a cabinet can impede the external detection of an in-cabinet fire condition.

VESDA can protect high/low voltage cabinet equipment by continuously sampling the internal cabinet environment. There are two methods, which may be implemented to protect high/low voltage cabinets.

In-Cabinet Sampling – Top Mounted:

Sampling pipe is positioned over the cabinet and capillaries are attached to the sampling pipe at appropriate intervals.  It is recommended that the capillary tube enter the interior of the cabinet to a depth of 25-50mm (1-2”).

In-Cabinet Sampling - Floor Void:

Sampling pipe is installed under the floor void and capillary tubes or riser pipes are attached at appropriate intervals.  Holes are then drilled in the floor and the base of the cabinet.  Capillary tubes or riser pipes are run through the bottom of the cabinet to the cabinet roof by a mounting clip.  It is recommended that the sampling hole faces downwards and should be 25-50mm (1-2”) below the interior of the cabinet top.

Above Cabinet Sampling:

Above cabinet sampling is achieved by locating the sampling pipe directly over the ventilation grille of the cabinet.  Stand-off posts are then used to mount the sampling pipe 25-50mm(1-2”) above the grille.  Each cabinet must have at least one dedicated sampling hole that faces the direct airflow from the cabinet.

Refer to Section 10: Cabinet Protection for further explanation on the above sampling methods.

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DESIGN GUIDE

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GLOSSARY

CFD Modelling:

Computational Fluid Dynamics modelling provides an accurate, computerised simulation of the airflow in a room and allows changes/additions in the placement of equipment to be factored without expensive real world tests.  It also provides an estimation of the direction that a particulate stream would follow in the modelled airflow.

Cable Riser/s

A vertical Cable Tunnel.

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Hydro-Electric Power Generation

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All Rights Reserved in accordance with its policy of continuing product and system improvement.  Vision products reserve the right to change designs or specifications without obligation and without further notice. VESDA is a registered trademark of Vision Products Pty Ltd. VESDA LaserPLUS, LaserSCANNER, LaserCOMPACT, VESDAnet, VESDAlink, ASPIRE, AutoLearn, VSM, VConfig and InfoWORKS are trademark of Vision Products Pty Ltd.