the invention concerns a fail - safe valve having a valve element , and a control motor being connected with the valve element via a driveline . it is endeavoured to ensure the tightness of the refrigeration system in a simple manner . for this purpose , it is ensured that the valve element is located inside and the control motor outside a closed valve housing , that the drive line has a magnetic coupling , which acts through the housing , and that the valve element is pressure - released . in addition , a resetting device is provided that causes the valve element to be returned to a predetermined position upon the undesired cessation of control motor operation .