Vision Systems VESDA, Руководство по конструкции

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VESDA
®
Refrigerated Storage Design Guide
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)
[4]
.
•
British Standard BS7974
[5]
.
•
SFPE Engineering Guide to Performance-Based Fire Protection
[6]
.
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.
Standard risk management concepts, like those listed below, are also often used for refrigerated
storage facility assessment:
•
AS/NZS 4360, 1999
[7]
.
•
SFPE Handbook Third Edition, 2002
[8]
.
Note: The SFPE Code Officials’ Guide to Performance-Based Design Review
[9]
is a very good
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?
3