Rubber backflow preventer

Studio A.S.E. implemented the project of a clapet check valve, meant to be installed on existing boiler bodies, in order to avoid gas backflow from the boiler's chimney when the burner is turned off.
The project had a peculiar goal:
to guarantee an effective closure, limiting the load losses of the fan to the maximum extent.
We searched for different solutions, interfacing with rubber manufacturers and moulding specialists, in order to identify the more adequate blending.
At the end, the costumer could choose among three different solutions, all equal in efficiency and compliance to the objective.