An isolator is an important device used in medicine, pharmacy, the nuclear process industry and similar. Metal isolator is not suitable for every application. In this case, the task may be better performed by a flexible isolator or an isolator made of TPU foil. Because hazardous substances are used in isolators, it is very important that the joints on the isolator are of good quality. The master's thesis presents some suitable joining technologies. A test rig designed specifically for checking the tightness or strength of joints is shown. At the test rig tests were performed on joints made with three different technologies, using an ultrasonic welding machine, a resistance welding machine and a heated tool welding machine. The pressure tests verified the joint loading capacity, the most common location, the type of burst and the size of the burst before bursting. It was discovered that by joining material, we achieve about a quarter less pressure compared to base material. Heated tool and resistance welder create more critical points than ultrasonic welder. Based on the obtained results and experience with operating the device, we have determined, by weighted criteria, the most suitable welding process for the manufacture of insulators.