A process and plant for laying a pipe in a trench comprising placing a flattened tubular preform in the trench, the perform having a reinforcement surrounding an inner seal, the reinforcement being impregnated with a resin, and inflating the perform in the trench. The catch pan device includes an intercepting pan that intercepts the curtain when coating is stopped and a substantially horizontal intercepting surface that intercepts the curtain only when the catch pan moves to start or stop coating. The movable cover panel may conceal the open area of the storage area when in its closed position and the movable cover panel may at least partially overlap the fixed cover panel when the movable cover panel is in its opened position. Each of the containers is caused to be in its first state as it moves through the first zone and in its second state as it moves through the second zone so as to impart motion to the loop.