Abstract: A fastening device for fluid tightly coupling a first duct body and a second duct body of a heat exchanger is provided. The fastening device includes a support member to couple with a connecting edge of the first duct body. The support member includes a pivot pin and a locking device disposed at an offset distance from the pivot pin along a radial axis of the fastening device. The fastening device further includes a pivot arm having a first end to engage with the pivot pin and a second end to engage with a flange of the second duct body. The locking device engages with the pivot arm and move the second end of the pivot arm relative to the pivot pin to fluid tightly engage the flange of the second duct body with the connecting edge of the first duct body.