We manufacture welded couplings for different types of sensors into pipeline or bioreactor. Coupling makes possible to change the sensor without interruption and at the same time provides sensor protection during sanitization. During the exchange of the sensor no shutdown is nessecary thanks to the possibility to unscrew the sensor. During the sanitization, the sensor is not involved with the sanitizing medium thereby the lifetime of the sensors (particularly with optical sensors measuring O2 content) is markedly extended and at the same time the calibrating intervals are prolonged too.