The invention relates to an installation and a method for manufacturing infusion bags with an access and an injection stopper. In addition, the invention relates to such a bag and to various injection stoppers. In the system according to the prior art, a tube piece, onto which the port is fitted, is welded into a bag. The port is not additionally fixed but is merely held by the tension in the tube. This can theoretically lead to impermeability problems. In contrast, in the new system proposed herein, the port is directly welded into the bag, so that the tube serving as an intermediate piece is dispensed with. The resulting advantage is more specifically that more than 30 mm of tubing can be saved in each bag, which not only makes the construction of the installation less expensive, but also eliminates the relatively expensive tubes. In addition, the tube and the port can be optionally welded with the same welding tool. The operator of the installation can decide whether he welds one tube and one port or two tubes. This does not require changing the tool. If the operator of the installation welds two tubes onto the bag, it is still possible to fit standard ports according to the prior art onto the tubes.