duct corner 20 TDC/TDF,TDC-20/TDC-30/TDF-40,grooving and wothout grooving,TDC corner ... ,duct clip.decoiler-roll forming-cutt duct corner 20:TDC unit is one of the two universal flange making ... 6 m/min. It is divided into four types: T-20,T-30,T-35,T-40 with their corresponding duct ... ducts in the DW144 standard, and has passed the HVAC PW/TMI(1987) pressure test, which is a speciality test for ...