Duct leakage reduces the air quantities at terminal points unless the total air quantity is adjusted to compensate. Leakage should be considered a transmission loss in duct systems. The farther air is conveyed the greater the loss will be. Key variables that affect the amount of leakage are;
i. Static pressure. (The higher the pressure the more leakage will occur.)
ii. The amount of duct. (the more duct the more opportunity for leakage there will be).
iii. The openings in the duct surface (the major contributors are joints and seams although access doors, rod penetrations and fastener penetrations also contribute).
iv. Workmanship (poor workmanship undermines the best construction standards).
Duck Leakage Testing should perform according to one of following standards;
* EN 1507
* SMACNA:HVAC AIR DUCT LEAKAGE TEST MANUAL
* BESA/DW 143
* EUROVENT 2/2
Step by step duct leakage testing;
Define the environmental conditions. (Temperature, pressure, gravitational acceleration, specific gas constant for tester fluid, density of tester fluid, density of water.)
Select the type of test station. (Orifice plate, venturi tube, laminar flow meter, rotameter and pitot tube)
Definition of required standard and leakage class. (TS EN 1507, SMACNA, DW143, DIN V 24194 and EUROVENT 2/2.)
Data input for applied test pressure, pressure drop accross orifice and tested surface area.