Vision Fire & Security
Refrigerated
Storage
Design Guide
March 2006
i
VESDA
®
Copyright
This document is protected by copyright under the laws of Australia and other jurisdictions
throughout the world. It must not by any means, either in whole or part, be reproduced,
communicated to the public, adapted, distributed, sold, modified, published except as permitted by
any laws or statute or with prior written consent of Vision Fire & Security Pty Ltd.
Copyright ©2006 Vision Fire & Security Pty Ltd ABN 25 008 009 514
Disclaimer
The manufacturer reserves the right to change designs or specifications without obligation and
without further notice. VESDA, LaserTEKNIC, LaserPLUS, LaserSCANNER, LaserCOMPACT,
LaserFOCUS, VESDAnet, VESDAlink, ASPIRE, ASPIRE2, AutoLearn, VSM, PSM, VConfig,
InfoWORKS, PROACTIV, PRECISION, VSC, ADPRO, FastTrace, FastVu, FastScan, Axiom, PRO,
Amux and Video Central are trade marks used under licence by the distributor.
Refrigerated Storage Design Guide
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Refrigerated Storage Design Guide
VESDA
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VESDA
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Refrigerated Storage Design Guide
Contents
1. Introduction.............................................................................................................................................. 1
1.1 About This Design Guide................................................................................................................. 1
1.2 Quick Reference............................................................................................................................... 1
2. Background Information......................................................................................................................... 2
2.1 Fire Safety Considerations In Refrigerated Storage Facilities......................................................... 2
2.2 Performance-Based Design............................................................................................................. 3
2.3 Key Design Considerations.............................................................................................................. 3
2.4 Why Use VESDA Smoke Detection?............................................................................................... 4
3. Designing For Effective Fire Protection................................................................................................ 4
3.1 Sample Pipe Material....................................................................................................................... 5
3.2 Positioning Pipes And Sample Holes............................................................................................... 5
3.3 Sample Pipe Insulation..................................................................................................................... 7
3.4 Sealing Sample Pipe Penetrations................................................................................................... 7
3.5 Compensating For Sample Pipe Contraction................................................................................... 8
3.6 In-rack Protection............................................................................................................................. 9
3.7 Ceiling Void Protection..................................................................................................................... 9
3.8 Other Areas To Be Protected......................................................................................................... 10
4. Preventing Condensation And Crystallization.................................................................................... 10
4.1 The Effects Of A Temperature Drop .............................................................................................. 10
4.2 Condensation On The Sample Pipe Outer Surface....................................................................... 10
4.3 Crystallization On The Sample Pipe Outer Surface....................................................................... 11
4.4 Condensation Inside Sample Pipes............................................................................................... 11
4.5 Crystallization Inside Sample Pipes............................................................................................... 12
5. Installation Considerations................................................................................................................... 12
5.1 Sampled Air Warming.................................................................................................................... 12
5.2 Heat Tracing................................................................................................................................... 14
5.3 Exhaust Air Treatment.................................................................................................................... 14
5.4 Water Traps.................................................................................................................................... 15
5.5 Integration With Pre-action Sprinklers............................................................................................ 15
5.6 Battery Backup............................................................................................................................... 17
6. Ongoing Considerations....................................................................................................................... 17
6.1 Running The VESDA System ........................................................................................................ 17
6.2 System Commissioning.................................................................................................................. 18
6.3 Service And Maintenance.............................................................................................................. 18
7. Appendix – Heat Tracing....................................................................................................................... 19
8. References.............................................................................................................................................. 21
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Refrigerated Storage Design Guide
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VESDA
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1. Introduction
1.1 About This Design Guide
Vision Systems Ltd has produced this Design Guide as a reference, to be consulted when
designing and specifying VESDA fire protection solutions for freezers, cold storage areas and
loading bays with temperatures ranging from minus 40°C (-40°F) to 18° C (65°F)
Unlike most commonly used passive fire detection devices, VESDA detectors are able to function
in sub-zero climates without losing their very early warning smoke detection capabilities. For this
reason, they have been extensively used in refrigerated storage facilities for many years and are, in
fact, the only Factory Mutual (FM) approved smoke detection and fire suppression activation
system for such facilities.
In this Design Guide we will discuss the relevant design considerations and make
recommendations regarding the most effective way in which to install a VESDA solution in the
particular refrigerated storage facility for which it is being designed.
Important Note: The information contained in this Design Guide should be used in conjunction
with specific local fire codes and standards. Other regional industry practices, wh ere applicable,
should also be adhered to.
Refrigerated Storage Design Guide
[1]
.
1.2 Quick Reference
The key design considerations presented in Table 1 are an overview only. They should be used in
conjunction with the remainder of the information presented in this Design Guide and in the
relevant VESDA System Design Guide
Table 1 – Key design considerations for a VESDA system in a refrigerated storage facility.
Component Key Design Considerations Detailed Information
VESDA Pipe
[2]
.
Pipe material and insulation
must be suitable for low
temperatures.
All connections in the pipe
network must be air-tight.
Sampled air MUST NOT be
subjected to vastly differing
sub-zero temperatures within
the freezer area.
The integrity of the freezer
must be maintained at all
sample pipe entrance points.
VESDA exhausted air must be
returned to the protected zone.
Sections 3.1, 3.3 and 3.5
Sections 3.4, 3.5 and 4.4
Sections 3.5, 4.1, 4.2 and 4.3
Section 3.4
Section 5.3
Only use water traps where the
external temperature is lower
than within the protected zone.
Avoid placing sample holes
close to the freezer entrances.
Avoid sampling directly from
the path of the chiller air
supply.
Sections 4.4 and 5.4
Sections 3.2 and 4.3 Sample Holes
Section 3.2
1
Refrigerated Storage Design Guide
Component Key Design Considerations Detailed Information
Table 1 Continued.
VESDA
®
VESDA Detector
Detectors must be installed
Section 1.4
outside the protected zone.
Detectors must be installed
Sections 3.4 and 4.4
inverted, to prevent water
entering them via the pipe
network.
Sampled air can be warmed
Sections 5.1 and 5.2
where necessary. Consider a
method.
Consider the battery backup
Section 5.5
required.
Integration With Pre-action
Suppression
Installing VESDA with a preaction sprinkler systems.
Section 5.6
2. Background Information
2.1 Fire Safety Considerations In Refrigerated Storage Facilities
According to statistics, released by the NFPA
facility arise from the following:
[3]
, the major fire risks within a refrigerated storage
• Electrical or mechanical faults in conveyor and other transport equipment.
• Electrical equipment, wiring and other equipment housed in the roof space.
• The lighting system.
• Hot spots resulting from maintenance operations.
• Discarded cigarette butts.
• Arson.
Due to the large amounts of plastic present in this type of facility, in the form of packaging
materials, a fire would produce large amounts of highly toxic and corro sive smoke which would
damage assets and endanger personnel. The large amounts of fuel available, in the form of stock
and the highly flammable light weight sandwich panels from which such facilities are constructed,
would also cause fires to spread quickly from one area to another. Table 2 provides guidelines for
those areas in a refrigerated storage facility that it is essential to protect.
Table 2 – Guidelines for areas to be protected.
Area Essential Recommended Optional
Freezers/Chiller Rooms
Coolers
Plant and Maintenance
Areas
Return Air Path Under the
Protected Area
Loading Bays and
Surrounding Areas
Office/Monitoring Area
Ceiling/Roof Voids
Within Racks
9
9
9
9
9
9
9
9
2
VESDA
®
In cases where a pre-action sprinkler system is to be included as part of the fire protection, the
VESDA system can be used to activate the release mechanisms as discussed in section 5.6.
2.2 Performance-Based Design
The flexibility of Performance-Based Design allows the fire protection system to be tailored to the
specific requirements of each individual refrigerated storage environment, with the commercial
drivers to manage the risks.
Detector spacing or, for a VESDA pipe, sample hole spacing is traditionally dictated by local
prescriptive codes and standards. In a more performance-based approach, each installation is
assessed according to its specific environmental conditions (ceiling height, airflow rate, expected
temperature range etc). Sample hole spacing and location can then be altered easily to suit the
particular performance requirements . Appropriate VESDA alarm sensitivities are determined by
conducting in-situ smoke tests and evaluating the system response.
Performance-based design concepts can be used in most countries as they adhere to many
international fire engineering guidelines, such as those listed below:
• International Fire Engineering Guidelines (Edition 2005)
• British Standard BS7974
• SFPE Engineering Guide to Performance-Based Fire Protection
While this alternative fire protection solution can be made to comply with local and national codes
and standards, for buildings and life safety, assessments of the environmental risks and
performance requirements, specific to the particular refrigerated storage facility, are also conducted
as part of the design process.
[5]
.
Refrigerated Storage Design Guide
[4]
.
[6]
.
Standard risk management concepts, like those listed below, are also often used for refrigerated
storage facility assessment:
[7]
• AS/NZS 4360, 1999
• SFPE Handbook Third Edition, 2002
.
[8]
.
Note: The SFPE Code Officials’ Guide to Performance-Based Design Review
source of information for Authorities Having Jurisdiction (AHJs) reviewing and assessing a VESDA
system design for a refrigerated storage facility.
2.3 Key Design Considerations
For the purposes of this Design Guide, the following temperature ranges apply to the various areas
to be protected:
• Freezers -40°C to -15°C (-40°F to 5°F).
• Chillers -9°C to 2°C (16°F to 36°F).
• Coolers and Loading Bays 0°C to 18°C (32°F to 65°F).
Important Note: VESDA Detectors MUST NOT be installed in sub-freezing environments.
A fire protection system designer would normally ask the following questions, when specifying and
designing a VESDA smoke detection system in a refrigerated storage facility:
1. What level of protection is required and how will fire safety be managed?
2. Is the integrity of the pipe network adequate with respect to being air-tight?
3. What temperature range and humidity will be experienced by pipes within the refrigerated
storage facility, pipes in any other areas to be protected and the detectors themselves?
4. Are there likely to be any future changes with regard to the function of the area due to
demand or operational needs? For example, might a refrigerated storage facility be
converted to a cold storage area?
[9]
is a very good
3
Refrigerated Storage Design Guide
5. What are the airflow characteristics of the protected area s, entrances and loading bays?
6. What are the pipe insulation requirements?
7. What effects might the defrost cycles and associated con densation have on fire protection?
8. What is the possibility of condensation occurring both within and on the outside of the pipe
network?
9. What is the configuration of racking within the areas to be protected?
10. How well sealed are the wall and ceiling insulation panels?
11. Is pre-action suppression to be included in the fire protection system and, if so, how will it be
integrated with the VESDA system?
2.4 Why Use VESDA Smoke Detection?
VESDA Aspirating Smoke Detection (ASD) systems have been used to protect refrigerated storage
facilities for many years. Most fire protection technologies which are designed to operate in
freezing conditions are not capable of early warning detection and are prone to being damaged by
equipment such as forklift trucks. The very early warning capability of VESDA detectors means that
they are able to detect the incipient (pre-combustion) stage of a fire which drastically reduces
business disruption, asset damage and the potential risks to the safety of personnel. The design
flexibility of VESDA systems also allows them to be used for the automatic activation of pre-action
suppression, both gaseous and sprinkler.
VESDA
®
The combustible nature of the types of materials normally stored in refrigerated environments,
combined with the very dry high airflow in such environments, creates a significant fire risk. Fires
will spread rapidly between cardboard or plastics packaging, grease impregnated materials, food
stuffs and wooden pallets. Hence, the earlier a fire can be detected the better.
The perishable nature of the goods, commonly stored in freezers or coolers, makes it essential that
any rise in temperature be avoided. Heat from a fire or a rise in temperature due to refrigeration
system down time, following a fire, would both result in stock spoilage and hence loss of revenue.
Even an incipient fire, in this type of environment, can lead to significant losses if not detected and
managed early. Stock exposed to low levels of smoke over an extended period of time will become
contaminated.
Other advantages of the VESDA system are that, with a properly designed system, performance
will be reliable and little influenced by condensation or the high airflows caused by blast chillers.
The deficiencies of other detector technologies in low temperatures are recognized by many
international codes and standards which regulate against the use of them in environments where
the ambient temperature is less than 0°C (32°F)
[10]
. Linear heat cables are permitted in freezers but
are prone to damage by forklift trucks and other common work procedures. Since VESDA detectors
are installed outside the protected area, only the sample pipe network is exposed to sub zero
temperatures. Being on the ceiling and inside voids makes it unlikely that the VESDA sample pipes
will be damaged.
Note: Unlike the FM approved VESDA system, linear heat cables are specifically for the activation
of pre-action suppression and cannot simultaneously provide the very early warning smoke
detection which may prevent the need for suppression.
3. Designing For Effective Fire Protection
In this section, design methodologies will be described with consideration for the different
requirements depending on the function of the particular area being protected.
TM
Important Note: The latest version of ASPIRE2
should be used for all pipe network designs.
4
, the VESDA sample pipe modelling program,
VESDA
®
3.1 Sample Pipe Material
The choice of pipe material will depend on where the pipe is to be located. For instance, installation
of ceiling mounted pipes can be made easier by using long lengths of pipe material suited to coping
with low temperatures and internal temperature fluctuations. Such materials include the Halogenfree Fire-retardant high Temperature (HFT) plastics, Acrylonitrile Butadiene Styrene (ABS) and
High Density Polyethylene (HDPE). Suitable materials and their properties are presented in Table 3
below.
Table 3 – Properties and recommended applications for pipe materials
Material Operating Temperature Thermal Contraction Recommended
Refrigerated Storage Design Guide
[11-14]
.
Applications
PVC -18°C (-40 to 120°F) 7.0 mm per 10 m per 10°C
(0.28” per 32.8 ft per 18°F)
HFT -40 to 140°C
(-40 to 284°F)
ABS -40 to 80°C
(-40 to 176°F)
CPVC -18 to 94°C
(0 to 201°F)
PE-80 -50 to 60°C
(-58 to 140°F)
PE-100 -50 to 60°C
(-58 to 140°F)
7.0 mm per 10 m per 10°C
(0.28” per 32.8 ft per 18°F)
10.1 mm per 10 m per 10°C
(0.4” per 32.8 ft per 18°F)
6.7 mm per 10 m per 10°C
(0.26” per 32.8 ft per 18°F)
20 mm per 10 m per 10°C
(0.79” per 32.8 ft per 18°C)
13 mm per 10 m per 10°C
(0.52” per 32.8 ft per 18°F)
An added advantage of using a continuous semi-flexible pipe material such as HDPE
reduction in the number of pipe junctions required.
3.2 Positioning Pipes And Sample Holes
Above -18°C (0°F)
Above –40°C (-40°F)
Above –40°C (-40°F)
Above -20°C (0°F)
Above –50°C (-58°F)
Above –50°C (-58°F)
[14]
is the
The various international codes and standards specify detection point spacing or maximum area of
coverage per detection point for a variety of different airflow rates, ceiling heights and structures
etc. In compliance with these prescriptive regulations, VESDA sample holes would be located in
the same positions as individual smoke detection devices. Alternatively, with reference to local
codes, the pipe and sample hole configuration can be determined by satisfying performance-based
design requirements.
Note: For Factory Mutual (FM) approved, refrigerated storage, VESDA installations the sample
holes should be placed as for heat detectors as outlined in the latest edition of the FM 8-29
Datasheet and Memorandum 0805
[1, 15]
.
Sample hole locations are usually represented by a grid like that shown below (Figure 1). The letter
X represents the sample hole spacing required according to local codes and standards.
5
Refrigerated Storage Design Guide
Figure 1 – Top view of a grid layout for VESDA sample holes.
VESDA
®
In some freezers, depending on the effectiveness and frequency of defrosting management, ice will
build up around the entrances. Under these circumstances, VESDA sample holes in the immediate
proximity may become blocked by ice. This is normal and can be managed by specifying an
appropriate system airflow fault threshold. The effects of blocked sample holes could be
compensated for as follows:
• By placing the sample hole closest to the entrances as far away as is legally permitted by local
codes and standards.
• By partial in-rack sampling near the entrances. Ice build-up is usually at the ceiling above the
doorways, seldom within the racks.
• By placing VESDA pipes away from the path of chiller air supplies.
Note: Sample hole diameter MUST be larger than 3 mm.
Referring to the grid layout shown above (Figure 1), there are two alternative approaches to pipe
network configuration design for optimal air sampling performance:
1. The pipes can be run along the ceiling inside the area to be protected as shown (Figure 2).
This technique minimizes the number of pipe penetrations through the wall s or ceiling and
can be applied in most practical situations. Sample holes MUST be drilled after installation in
this case.
2. The pipes can be positioned outside the area to be protected with smaller diameter capillary
tubes (16 mm (3/4 inches) outer diameter) fed through the ceiling insulation into the
protected area as shown (Figure 3). This method requires one ceiling penetration per
capillary tube and more pipe connections. All penetrations must be adequately sealed to
prevent the formation of ice resulting from the entry of humid air or condensation. This
approach is only appropriate where the refrigerated storage facility has a ceiling void. The
capillary sampling tubes should be as short as possible; less than 4 m (13 ft) being
recommended. They MUST also be sealed during installation.
6
VESDA
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Refrigerated Storage Design Guide
Figure 2 – Ceiling mounted VESDA pipes.
Figure 3 – Example of capillary air sampling.
Note: It is recommended that all drilling of penetration points, and the sealing of such points, be
performed by appropriately experienced personnel.
3.3 Sample Pipe Insulation
Where pipe insulation is needed, use a material such as Armaflex or similar. Armaflex insulation
has a temperature range of -40°C (-40°F) to 105°C (221°F), a density of 88 to 105 kg/m
very flexible. For a 25 mm (0.98”) internal bore pipe, a single layer of insulation 9 mm (0.35”) thick
is adequate.
3.4 Sealing Sample Pipe Penetrations
Pipe penetrations, through ceiling or wall insulation panels MUST be properly sealed with a solid
(Urethane foam) and/or flexible (mastic) material. To enhance air-tightness, a seal and/or insulation
boot could also be installed at the penetration point as shown below (Figure 4). Consult local Wall
Panel Suppliers for more detailed instructions.
3
and is
7
Refrigerated Storage Design Guide
Figure 4 – Example of pipe
penetration with an insulation
boot and drip tray
VESDA
®
In order to avoid condensation formation at the penetration point, the section of pipe exiting the
protected area MUST be insulated as shown (Figure 4). A tray can be used to collect any water
condensation on the pipe surface.
3.5 Compensating For Sample Pipe Contraction
Mounting clips, used to secure VESDA pipes to the ceiling, MUST not restrict longitudinal
movement of the pipes as they expand or contract due to temperature variations. This is especially
important where the pipe network is installed before the refrigerators are turned on. For example,
according to its thermal expansion coefficient, an ABS pipe will contract by 0.1% for every 10°C
(50°F) drop in temperature. This equates to a 40 mm (1.57 inch) reduction in length for a 40 m
(131.2 ft) pipe and will result in disconnection of pipe sections in cases where the pipes were
installed in temperatures well above the intended operating temperature.
Note: Refer to Table 3 for the thermal properties of other commonly used pipe materials.
To prevent pipe disconnections, make allowance for pipe contraction along the length of the pipes.
Saddle or offset clips should be use to secure the VESDA pipes to the ceiling as shown below
(Figure 5).
Saddle Clip
Offset Clip
Pipe Clip (UK)
Figure 5 – Examples of pipe network supports.
8
VESDA
®
Offset clips are preferable since they attach to the ceiling via an adhesive pad and, if required, can
be screwed on to the ceiling. The design of offset clips also allows easy movement of the pipes
during expansion or contraction.
To further minimise the possibility of pipe disconnections, pipe mounting clips MUST not be
positioned next to pipe joiners. Clips MUST also be more than 300 mm from the ends of the pipes
so that a pipe contraction will not cause its end caps to be forced off.
3.6 In-rack Protection
In most cases, placing a VESDA pipe network on the ceiling is all that is needed. However, sample
pipes can also be located along the racks used for storage in the refrigerated area as shown below
(Figure 6).
Refrigerated Storage Design Guide
Figure 6 – Example of in-rack air sampling.
Wherever possible, the in-rack sample pipe should enter the protected area through the wall at the
height that the pipe will be positioned in the rack.
Note: Capillary air sampling is not recommended for in-rack sampling.
3.7 Ceiling Void Protection
Very early smoke detection is essential due to the high incipient fire risk presented by the electrical
cabling and refrigeration control equipment normally housed in the ceiling void. Some local codes
and standards specify that ceiling void protection must be a component of the fire protection
system.
The sample hole spacing is determined, with reference to local codes and standards, according to
the grid presented earlier (Figure 1) and is shown below (Figure 7).
Figure 7 – Example of ceiling void air sampling.
9
Refrigerated Storage Design Guide
The VESDA detectors used to protect the ceiling void MUST be configured as individual fire zones.
Ceiling void pipes MUST NOT enter any other areas, nor should ceiling void detectors be used to
simultaneously monitor areas outside the ceiling void.
3.8 Other Areas To Be Protected
For non-refrigerated storage areas such as those used for control, monitoring, loading and office
space, the sample hole spacing and pipe network layout are identical to those for the general office
environment described in the VESDA System Design Guide
standards where applicable. Detector sensitivity can be adjusted to meet performance
requirements.
Note: It is worth considering high sensitivity smoke detection in the areas containing refrigeration
control and support equipment, since smoke or fire damage in these areas would disrupt business.
[2]
, with reference to local codes and
4. Preventing Condensation And Crystallization
4.1 The Effects Of A Temperature Drop
Condensation will occur when the air temperature drops below its due point. The result is the
formation of water droplets (if the due point is above 0°C (32°F)) or ice crystals (if the due point is
below 0°C (32°F))
the sampled air is cooled as it passes along the pipe through an area of lower temperature than
that from which the air was sampled. On the outer surface of pipes, condensation is expected and
can be tolerated.
[16]
. Inside the VESDA pipe network, condensation is unlikely and will only occur if
VESDA
®
During system design, all areas to be protected must be categorised according to the criteria listed
below:
• The temperature and humidity changes that will occur if the function of the protected area is
changed, for example, from a chiller to a cooler.
• The points in the pipe network which are most likely to be prone to condensation. This is done
by assessing the temperature of the sampled air and the temperature of the air surrounding the
sample pipe network.
• The air-tightness of the pipe network, including the detector exhaust pipe.
• The distances, from both the protected area entrances and chiller air supply paths, of both the
sample pipe and sample holes.
4.2 Condensation On The Sample Pipe Outer Surface
Condensation occurs on the outer surface of the sample pipes and capillary tubes where they exit
the cold storage area and enter warmer environments such as a ceiling void or other non-freezer
areas. Depending on the temperature of the pipe surface, in these areas, water droplets or ice
crystals will form. A water tray should be used to collect any liquid before it spills over the ceiling
insulation panels as shown below (Figure 8).
Note: The water tray must be large enough to allow evaporation to occur at an acceptable rate to
prevent overflow.
10
VESDA
®
Refrigerated Storage Design Guide
Figure 8 – Example of a
water tray.
4.3 Crystallization On The Sample Pipe Outer Surface
Occasionally, ice will form on the exterior of the sections of sampling pipe close to the refrigerator
entrances as shown below (Figure 9). This ice build up is normal and has no adverse effect on the
operation of the VESDA system, provided that sample holes are not located in the susceptible
sections of pipe where they can become blocked. Sample holes nearest to the entrances should be
sprayed with silicone to prevent ice formation.
Figure 9 – Example of ice formation on
sample pipes close to the refrigerator
entrance.
4.4 Condensation Inside Sample Pipes
Condensation inside sample pipes, outside the protected area is rare. However, it can occur if the
function of the protected area changes and/or as a result of seasonal temperature variations. For
example, if a chiller (-9°C, 16°F) is converted to a cooler (8°C, 46°F), condensation may form
inside the pipes outside the cooler during winter when the temperature could conceivably drop
below 8°C (46°F) .
The following measures will ensure that condensation forming in the pipes doe s not enter the
detector:
• Install the detector in the inverted position with the pipe entering it from below as shown above
(Figure 2).
• Install a water trap as discussed later in section 5.4.
e
11
Refrigerated Storage Design Guide
4.5 Crystallization Inside Sample Pipes
In order to minimise the possibility of ice plug formation inside the sample pipe, 90° elbow junctions
between pipe sections should be avoided. Where it is essential to change the orientation of the
pipe from horizontal to vertical, or vice versa, large radius bends should be used.
The chiller air supply is several degrees lower than the air in the rest of the chiller so, to prevent ice
from forming and blocking the sample holes, sample pipes MUST NOT be installed in the direct
path of the chiller’s supply air vent. Doing so will lead to crystallisation when the warmer ambient
air in the protected area enters the cool pipe. If for practical reasons, this cannot be avoided, the
pipe MUST be insulated as shown below (Figure 10).
VESDA
®
Figure 10 – Example of pipe insulation to combat ice
formation in pipes directly in the path of the chiller air
supply (the top is a good design, the bottom is not).
Important Note: Pipes MUST NOT run from a high temperature area into a lower temperature
area. Separate VESDA detectors should be installed in the chiller, cooler, ceiling void, and office
areas.
5. Installation Considerations
5.1 Sampled Air Warming
For optimum detection and ease of maintenance access, the VESDA detector MUST be installed in
a location where it is unlikely to experience sub-zero temperatures. Low temperature sampled air
can be easily warmed up, before it reaches the detector, by extending the sample pipe length
beyond its point of exit from the cooler protected area. The warmer air outside the pipe near the
detector will heat the cold sampled air within it. Usually, only a short pipe extension is necessary.
The charts below (Figure 11 to Figure 13) provide conservative estimates of the pipe extensions
required, to raise the temperature of the sampled air to an acceptable value, for a number of
commonly used pipe materials and range of flow rates. All calculations assume an external
ambient temperature of 20°C (68°F) and a sampled air temperature of 4°C (39°F).
12
VESDA
®
Refrigerated Storage Design Guide
12
40 l/min
10
8
ABS Pipe Length (m)
30 l/min
6
20 l/min
4
2
0
-40 / -40 -30 / -22 -20 / -4 -10 / 14 0 / 32
Sampled Air Temperature (deg C / F)
40
35
30
25
20
15
10
5
0
ABS Pipe Length (ft)
Figure 11 – Chart showing the estimated required ABS pipe
extension for sampled air warming.
6
40 l/min
5
20
16
4
Cu Pipe Length (m)
3
2
1
0
-40 / -40 -30 / -22 -20 / -4 -10 / 14 0 / 32 10 / 50
30 l/min
20 l/min
Sampled Air Temperature (deg C / F)
Figure 12 – Chart showing the estimated required Copper pipe
extension for sampled air warming.
12
8
4
0
Cu Pipe Length (ft)
13
Refrigerated Storage Design Guide
9
40 l/min
8
7
VESDA
®
30
25
6
PE-100 Pipe Length (m)
30 l/min
5
4
20 l/min
3
2
1
0
-40 / -40 -30 / -22 -20 / -4 -10 / 14 0 / 32
Figure 13 – Chart showing the estimated required PE-80/PE-100 pipe
5.2 Heat Tracing
In extreme cases where there is no space to run pipe extensions or the external temperature varies
widely, heat tracing may be employed for sampled air warming. However, this approach to warming
sampled air is NOT recommended by Vision Fire & Security as it has not been validated by Factory
Mutual (FM).
20
PE-100 Pipe Length (ft)
15
10
5
0
Sampled Air Temperature (deg C / F)
extension for sampled air warming.
Important Note: The Appendix contains information on the copper pipe and heat tape lengths
required for sampled air warming. No design guidelines will be given here. If wishing to use heat
tracing, appropriately qualified Engineers MUST be consulted as to the most suitable method to be
used.
5.3 Exhaust Air Treatment
Air from the VESDA exhaust pipe MUST be returned to the area from which it was sampled as
shown below (Figure 14).
Wall penetration
Figure 14 – Examples of a VESDA exhaust pipe
being fed back into the area from which the air
Ceiling Penetration.
sample was taken.
14
VESDA
®
This closed loop system will prevent pressure differences, caused when the VESDA detector is
powered down for any length of time, from introducing warm and humid air into the refrigerated
storage area via the VESDA exhaust port. Pressure differences will also result in unwanted airflow
faults.
The return pipe from the exhaust should be as short as possible and its penetration, into the
protected area MUST be air-tight.
Important Note: All inlet and exhaust pipes MUST be closed off whenever the system is powered
down or detectors are removed for maintenance.
5.4 Water Traps
Water traps are not a requirement of the VESDA smoke detection system. As discussed
previously, they are only necessary under vastly varying environmental conditions where internal
sample pipe condensation is a possibility. An example of a water trap is shown below (Figure 15).
Refrigerated Storage Design Guide
Figure 15 – Example of a water trap.
To install a water trap, a T section of pipe must be fitted to the pipe entering the inverted detector.
Water will pool at the stop valve on the downwards pointing arm of the T. The transparent section
of pipe allows maintenance personnel to see when water is building up, before it rises above the
intersection with the main sampling pipe, and release it via the stop valve. An end cap could be put
on the pipe in place of the stop valve. If no condensation is evident after some time, the water trap
can be removed.
Important Note: Water trap stop valves and end caps MUST be replaced as soon as the water
has been drained. Leaving the pipe open will affect the airflow.
5.5 Integration With Pre-action Sprinklers
The VESDA smoke detection system can also be used to activate pre-action sprinklers, if installed.
For the purposes of pre-action sprinkler activation, VESDA protection in-rack is usually not required
even where there are in-rack sprinklers. However, it is important to refer to the FM memorandum
[15]
0805
for further details.
15
Refrigerated Storage Design Guide
The procedure for integrating VESDA with pre-action sprinklers is outlined below:
1. Use ASPIRE2 to design the pipe network and determine Maximum permissible Transport
Time . For FM approved, refrigerated storage, VESDA installations, sample hole spacing
should be the same as heat detector spacing as per the latest edition of the FM8-29
Datasheet and Memorandum 08-05
2. Install the VESDA pipe network on the ceiling as shown below (Figure 16).
[1, 15]
VESDA
®
.
16
Figure 16 – Arrangement of the VESDA pipe network and
sprinkler heads on the ceiling.
3. Set the VESDA Alert alarm threshold for early detection and intervention.
4. Set the VESDA Fire 1 alarm threshold for pre-action sprinkler activation as in dicated in
Table 4.
Note: Delays can be configured for both of these alarms.
The smoke thresholds in Table 4 are absolute values, hence the environmental background level
must be taken into account. All values are recommendations only, actual values being dependent
on individual site conditions such as air change rate, storage rack height etc. Before using any
values, the system performance MUST be verified by the commissioning test (refer to section 6.2).
Any VESDA Fire 1 alarm shall put all sprinkler valves, in that particular fire zone, into armed mode.
VESDA
®
Refrigerated Storage Design Guide
Table 4 – Design guidelines for VESDA fire alarm settings
Enclosure Size Small < 500 m
(5400 sq.ft)
Fire Alarm (General
10 m (30 ft) or less)
Fire Alarm
(High Ceiling more
2%obs/m
(0.61%obs/ft)
1.5%obs/m
(0.46%obs/ft)
2
Medium 500 –
1000 m
10800 sq.ft)
2%obs/m
(0.61%obs/ft)
1.5%obs/m
(0.46%obs/ft)
2
(5400 –
Large 1000 –
1500 m
– 16200 sq.ft)
1.5%obs/m
(0.46%obs/ft)
1%obs/m
(0.31%obs/ft)
[17]
2
(10800
.
Extra Large
> 1500 m
2
(16200 sq.ft)
1%obs/m
(0.31%obs/ft)
1%obs/m
(0.31%obs/ft)
than 10 m (30 ft))
Maximum Transport
Time Allowed per
Zone (s)
See Note Below
and consult local
codes.
110 110 110
Note: For small enclosures, the Maximum Transport Time Allowed is a function of the ceiling
height H and equals 0.14H – 0.8H + 80. If the Maximum Transport Time Allowed cannot be
achieved, install additional detectors in the area. If the Transport Time is close to the maximum
allowed, consider reducing the fire alarm threshold by 10 to 20% to compensate. Ceiling height
restrictions are for FM approval. Remember also to consult local codes and standards for Transport
Time requirements.
5.6 Battery Backup
When using a VESDA system for pre-action suppression activation, in the event of a power outage,
a secondary power supply MUST be available. This power supply needs to be capable of running a
single VESDA detector for a total of 90 hours. This is in compliance with the fact that approved
control panels for the automatic release of pre-action or deluge sprinkler systems must have 9 0
hours of standby power plus 10 minutes worth of power to operate the sprinkler system and
[17]
alarms
.
Where the VESDA system is being used for very early warning smoke detection alone, refer to
local codes and standards for the battery backup required.
6. Ongoing Considerations
6.1 Running The VESDA System
For a new refrigerated storage facility, it is preferable that the VESDA system be powered up and
running while the refrigerators are being commissioned. This allows the detectors to adjust
gradually to the decreasing sampled air temperature.
If installing VESDA detectors in an existing facility, it is recommended that the pipe network inside
the refrigerated areas be installed first and that all points where pipes exit these areas be blocked
off. This prevents humid air being transferred into the protected area from outside. The blockages
can be removed once the rest of the pipe network and detectors, outside the refrigerated areas,
have been installed and connected.
Note: It may be necessary to construct enclosures around detectors to protect them from the
weather or mechanical damage.
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Refrigerated Storage Design Guide
6.2 System Commissioning
Once the VESDA system has been installed, its performance and pipe network integrity can be
verified using the ASPIRE2 pipe modelling program. A range of sampled air temperatures may be
input to determine Maximum Transport Times for each zone. Calculated Transport Times should
be applied conservatively. Smoke tests can then be used to check system performance for both
smoke detection and pre-action suppression activation.
6.3 Service And Maintenance
The VESDA system shall be serviced and maintained according to both the local codes and
standards and the instructions provided in the Maintenance section of the VESDA System Design
Manual
The frequency of sample pipe inspection and testing can be determined by the rate of ice build-up
to ensure that sample holes do not become blocked.
[2]
.
VESDA
®
18
VESDA
)
)
®
7. Appendix – Heat Tracing
There are several techniques for warming sampled air including water heaters, electrically heated
tape and passing the pipe through an area that has been heated to 5-10°C (41-50°F). Electrically
heated tape is preferred as it is easy to install. An example of a pipe covered with heat tape is
shown below (Figure 17). If the surface temperature is over 30°C (86°F), the pipe must be
insulated.
Refrigerated Storage Design Guide
Figure 17 – Example of heat tracing
with heat tape.
Raychem heat tape 5BTV2-CT or 3BTV1-CR can be used.
The following charts provide estimates of copper pipe and heat tape lengths required for heat
tracing. Variations in ambient temperature are assumed to be negligible due to pipe insulation. The
surface of the pipe is kept at a temperature of 35°C (95°F) and the tape is wound around it at 100
mm (4”) intervals along its length.
2
40 l/min
1.5
Cu Pipe Length (m
1
0.5
0
-40 / -40 -30 / -22 -20 / -4 -10 / 14 0 / 32 10 / 50
30 l/min
20 l/min
Sampled Air Temperature (deg C / F)
6
Cu Pipe Length (ft
4
2
0
Figure 18 – Estimates of copper pipe length for heat tape.
19
Refrigerated Storage Design Guide
VESDA
®
3
40 l/min
2
Heat Tape Length (m)
-40 / -40 -30 / -22 -20 / -4 -10 / 14 0 / 32 10 / 50
30 l/min
20 l/min
1
0
Sampled Air Temperature (deg C / F)
Figure 19 – Estimated heat tape length.
10
8
Heat Tape Length (ft)
6
4
2
0
20
VESDA
®
8. References
[1] FM Global (2000) Property Loss Prevention Datasheets 8-29.
[2] Vision Fire & Security (1997) VESDA System Design Guide.
[3] NFPA Fire Analysis & Research Division (2003) Selections from the U.S. fire problem overview
report. Leading causes and other patterns and trends Storage properties excluding dwelling
garages.
[4] Australian Government State and Territories of Australia (2005) International Fire Engineering
Guidelines.
[5] British Standard BS 7974 (2001) Application of Fire Safety Engineering Principles to the Design
of Buildings – Code of Practice.
[6] SFPE (2000) Engineering Guide to Performance-Based Fire Protection Analysis and Design of
Buildings.
[7] Australian Standard AS/NZS 4360 (1999) Risk Management Standard.
[8] SFPE (2002) Handbook of Fire Protection Engineering, 3
[9] SFPE & ICC (2004) The Code Officials’ Guide To Performance-Based Design Review.
[10] NFPA (2002) National Fire Alarm Code (72).
[11] The Plastics Pipe Institute, Inc. (1999) Suggested Temperature Limitations for the Operation
and Installation of Thermoplastic Pipes in Non-pressure Applications, TN-11/99.
www.plasticpipes.org.
[12] PPFA (2003) Information & Technical Guide – ABS Pipes & Fittings,
[13] Clipsal (2003) HFT Conduits & Fittings,
[14] Fisher, G. (2002) Planning Fundamentals Industrial Piping Systems,
www.piping.georgefisher.com.
[15] FM (2006) Memorandum - Engineering Bulletin 08-05.
[16] ASHRAE (2003) Psychometric Chart, www.ashrae.com.
[17] FM Global (2003) Property Loss Prevention Data Sheet 5-40 Fire Alarm Systems.
rd
www.clipsal.com.
Refrigerated Storage Design Guide
Edition.
www.ppfahome.org.
21
Refrigerated Storage Design Guide
VESDA
Disclaimer On The Provision Of General System Design
Recommendations
Any recommendation on system design provided by Vision Fire & security Pty Ltd (VFS) is an
indication only of what is considered to be the most suitable solution to meet the needs of the
common application environments described.
In some cases the recommendations on system design provided may not suit the uniqu e set of
conditions experienced in a particular application environment. VFS has made no inquiry nor
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which may be made or given by any statutory or any other competent authority in respect of or
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®
VFS products must only be installed, configured and used strictly in accordance with the General
Terms and Conditions and the technical documentati on available from VFS. VFS accepts no
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22
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