Air-tightness of the AF and BF Circular Flanges (ZI-702)
(Test results analysis of December 1984)
Test Pressure: 1000 Pa
With no sealing measures, the following leakages can be observed with the AF and BF circular flanges
a) 2 Circular Flanges 500 mm Ø have a total leakage of 0,3 l/s
b) One running meter circular flange has a leakage of 0,1 l/s (for comparison‘s sake a running meter Pittsburgh seam has a leakage rate of 0,25 l/s and a running meter of METU-SYSTEM rectangular flange a leakage rate of 0,13 l/s).
c) On a 500 mm Ø circular duct with a distance between the flanges of 3 m (total surface 4,7 m2) the leakage amounts to 0,064 l/s/m2, or 23% only of the allowed leakage of the DIN EN 12237 (Eurovent 2/2) Class C. Even if the leakage was multiplied by four, the value would still be lower than the Class C (for the DIN EN 12237 Leakage Classes please refer to the Additional Information ZI 27 and 28).
It can therefore be assumed, in view of the above, that both the flanges and the duct are air-tight.
More precise investigations regarding leakage reasons have shown that the contact between the sealing lip and the duct is air-tight over practically the entire circumference. Most of the leakage can be observed in 4 to 5 locations along the duct circumference. The most important leakage occurs at the crossing between the sealing lip and the seam of the air-duct. the other leaks are due to rough irregularities in the inner surface of the duct.
Sealing measure consisting of applying mastic inside the seam over a distance of 5 cm
a) 2 Circular Flanges 500 mm Ø have a total leakage of 0,2 l/s.
b) One running meter circular flange has a leakage of 0,064 l/s.
c) On a 500 mm Ø circular duct with a distance between the flanges of 3 m (total surface 4,7 m2) the leakage amounts to 0,042 l/s/m2, or 15% only of the allowed leakage of the DIN EN 12237 (Eurovent 2/2) class C. Even if the leakage was multiplied by six, the value would still be lower than the Class C.
The circular duct seam is the main cause for leakage. By applying mastic in the seam the total leakage is reduced by one third.
Applying sealant inside the Circular Flange pocket and/or inside the duct between the flanges and the duct wall
Test Pressure 1000 Pa: Leakage 0
Test Pressure 2000 Pa: Leakage 0
Test Pressure 3000 Pa: Leakage 0
Test Pressure 4000 Pa: Leakage 0
When performed with care, the above measures allow to achieve perfectly air-tight connections at higher pressure levels as well.
Super-tight Connections without any Additional Measures
To achieve the requirements of the DIN EN 12237 (Eurovent 2/2) class D (ATC2) or higher (ATC1) without having to take any special extra measures or precautions, we invite you to contact us. The new METU-FORM system of laser welded ducts, fittings and connections have been developed to provide solutions for these extreme cases.
AF Circular Flanges and SR Joining Clip Air-tightness Certification from BSRIA:
We herewith confirm that internal tests, as well as tests conducted by the independent testing institute BSRIA in the UK (Test Report 11352/1 dated March 1994) have demonstrated that the AF circular flanges along with the corresponding SR joining clips fitted with a polyethylene (PE) gasket reach the DIN EN 12237 class C, assuming that they have been properly mounted on plain or spirally wounded round ducts (without stiffening ribs) according to the instructions provided in our "METU SYSTEM Katalog" (The German version prevails). Additional information about the above-mentioned tests (ZI-713) and the polyethylene gasket (ZI-202) are available upon request.
HVAC TM1 (DW/142), Ref. 11352/1 (March 1994)
Pressures: +2000Pa, +2500Pa, -500Pa, and -750Pa.
AF 125: Class C on Spiral Duct
AF 90: Class C on Spiral Duct
AF 45: Class D on Spiral Duct
MU 315: Class D on Spiral Duct
BF 20, LF Ends: Class D on Straight Duct
BF 50, LF Ends: Class D on Straight Duct
LF 45, BF Ends: Class D on Straight Duct
AF 125: Class D on Spiral Duct
AF 90: Class D on Spiral Duct
AF 50 + BF 50: Class D on Spiral Duct
BF 90 + LF 90: Class D on Straight Duct
UF 125 + BF End: Class D on Straight Duct
AF 20: Class C & D on Straight Duct
Corresponding SR Joining Clips with PE gasket have been used to connect the circular flanges together.
The additional information have been compiled carefully. They are only intended to provide counsel. They are the result of internal tests and information provided by our suppliers. There is no guarantee for completeness and accuracy. More precise information can only be made available through focused tests on a case by case basis. The provided indications do not discharge the user from conducting his own tests. Please make sure that the product is suitable for the intended use. Changes, errors and omissions excepted. Free translation: the German version prevails.