Feature
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Round steel ducts come in standard profiles .
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A Fabric / textile duct installation in a large indoor sports facility .
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A large round duct bend connection design eases the flow of air with 45 degree sections .
system is light weight , and easy to modify while its major limiting characteristics include cost , acceptance in standards , weight , and fire impact risk .
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Ducting at work in an open industrial style design .
Fabric Fabric ducting , also known as textile ducts , are made of special permeable polyester material and can be used in new buildings or retrofit projects . Fabric ducts are used to disperse air in open ceilings and underfloor applications . Condensation is not a concern with permeable fabric as permeable fabric prevents the formation of condensation on the duct surface .
Systems that utilise fabrics provide solutions for various applications and it has been proven by some academic studies that fabric ducting reduces energy costs significantly .
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Leakage typically occurs at joint-corners . To mitigate this , manufacturers use a flexible silicon-type material as a sealer .
Flexible Ducting This product consists of a duct inner liner supported on the inside by a helix-type wire coil and covered by an insulation with a flexible vapor barrier jacket on the outside ( most often a type of foil ). Flex ducts are used primarily to connect the main ducting trunk or branches to supply points as they allow easy adaptation and flexibility in installations . This product does have significantly more friction loss than other ducting materials and so “ runs ” should be as short as possible ( 1.5metres maximum ) and be tensioned or stretched as tightly as practicable .
SMACNA manufacturing guidelines indicate recommended specifications based on duct size – and have several similarities to the South African standard for low pressure systems :
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RACA Journal I October 2022 www . refrigerationandaircon . co . za