Galvanized Air Ducts-22574

Product Code: 7

Galvanized Air Ducts
Our air ducts manufactured to carry air are manufactured from TSE certified galvanized, stainless steel or aluminum plate. They are impact resistant and impermeable. Materials used to manufacture the duct, elbow, shaped parts and all branches comply with TS-EN 1505 and its manufacture complies with to EN 10142. In addition, TUV-certified high-strength, leak-proof flange and corner parts are used as joining equipment.
Materials of the duct and fittings are automatically cut by plasma cutting machine with high precision to minimize the waste in accordance with the dimensions entered into the computer. All air ducts, elbows and reductions are closed without manual labor with automatic clamping machine. Sealing is ensured with elastic silicone after the manufacture and spot points are painted with chrome against corrosion. Each manufactured part is labeled according to line and position numbers. This process provides great convenience in installation. TUV certificated flange used in manufacture has high sealing due to its special design. Thus, our ducts have SMACNA C Class high permeability. Galvanized sheet air ducts which are installed as air carrying line between the air-conditioning plant and blow and suction vents can be covered with decorative materials like plasterboard etc. upon request.


Leakage in Air Ducts

Air leakage in the duct system should be within desired limits. This is so important for following considerations.
• Eliminating additional energy cost arising from utilization of devices with efficiency greater of lower than required and preventing energy waste
• Preventing additional labor costs required to distribute air due to high amount of air leakage
• Minimizing the sound caused by air leakage
• Minimizing the problems faced especially in systems where frequency converters are used.
• Zero leakage is a preferred property in distribution systems for hazardous gases but it is not the objective in normal practice. Such an objective requires to much labor and time and will increase the cost.


Air Leakage Space Relationship

Even though the amount of leakage in round or rectangular air ducts varies in accordance with the dimension of the duct or frequency of fittings used, it varies in proportion to the area of air duct in practice.


Air Leakage Pressure Relationship

Any leakage in an orifice of the duct area taken into consideration at a given pressure will vary according to the shape of the orifice. Measurements of leakage orifices of the installed duct system will vary. Accordingly, it is impossible to provide a precise value regarding pressure/air leakage relationship. However the tests show that the air leakage is proportional to 0.65 of compressive strength. This value is accepted by EUROVENT in preparation of document 2/2.


Acceptable Air Leakage Limits

• Pressure limits in the ducts should be primarily considered to address the allowed air leakage limits.
• All ducts operating at high pressure should be tested and their conformity with air leakage limits should be determined. Leakage tests of duct systems under medium or low pressure should be compulsory in standards. If pressure testing of the ducts under medium or low pressure is required, this matter should specified in specifications of the project. The allowed air leakage is grouped under four pressure leakage standards in DW 142.
The values specified for classes A, B and C are the same as those specified in Eurovent. DW 142 specifies impermeability standard Class A for low pressure duct systems, Class B for medium pressure duct systems and Classes C and D for high pressure duct systems.
• Basing on the values given in the table, the allowed air leakage amounts in each pressure class are calculated.


Air Leakage - Total Air Volume Relationship

• Since air leakage depends on the surface area of the duct, air leakage cannot be specified as percentage of total air volume. In addition, some certain amount of air leakage percentage cannot be given as an acceptable value in terms of performance standard.
However, numerous tests have shown that the total air leakage will be 6% of total air volume in low pressure air-conditioning ducts under operating conditions, 3% in medium pressure air-conditioning ducts and 2-0.5% in high pressure air-conditioning ducts. Figure 1.4 shows air leakage amounts as percentage of total air volume.
The designer should have the knowledge of possible and allowed percentages of air leakage in a duct system. Therefore, the designer calculates the total surface area of the duct in pressure classes (Classes A, B and C), estimates average pressure difference of the system and by adding the operating volume, finds total leakage and its proportion to volume by using Table 11. In addition, the designer specifies acceptable total air leakage. The designer estimates the pressure difference of the system by calculating total area of duct surface and determines the required pressure class in the light of this information.

Air Leakage Testing of the Duct

A - Leakage Class will be determined. CLASS
CLASS A up to 500 Pa. positive pressure
CLASS B up to 1000 Pa. positive pressure
CLASS C up to 2000 Pa. positive pressure
CLASS D up to 2500 Pa. positive pressure

B - Test Pressure will be determined.
Test pressure of each zone to be tested should be determined and test pressure should meet the average pressure.
Pm = Average operating pressure,
P1 = Operating pressure at the start of the duct,
P2 = Operating pressure at the end of the duct

C - Test Zones will be determined.
Test instrument and operating conditions in the field should be taken into consideration

D - Duct Area to be tested will be calculated
E - Allowed Total Air Leakage will be calculated
F - Test Procedure
• F1. Air leakage in the ducts is measured by a special device.
• F2. All openings in test zones (vent nozzles, branch nozzles, etc.) are sealed.
• F3. Test instrument is properly connected to air duct, fan is actuated and its speed is gradually increased. The aim is pressurizing the duct from inside and reaching the specified test pressure value. This value is read by the manometer mounted on the duct. After reaching the average static pressure value, fan should run for 5 minutes before the measurement is made.
• F4. The pressure difference read from the second manometer connected to the pipe between the fan and the duct shows the pressure basing on the velocity of air. This shows that there is an air movement inside the duct even if it is all sealed, that is there is some amount of air leakage. The aim is not zero leakage, so if the amount of leakage is within the acceptable air leakage limits of selected leakage class, this is an acceptable result. The leakage in the duct section is determined basing on the pressure value, circuit tables or diagrams provided by the manufacturing company. Period of the test should be 15 minutes and the increase in the leakage should be observed.
• F5. The results are included in the test report.