I am trying to set up a control system for a tank that is blanketed with a hydrocarbon gas (vs. inert gas). In order to improve the safety of the operation of the tank, I was thinking I would initially control the system with an oxygen analyzer linked to the blanketing control valve. Control valve would use the oxygen value and control purge / blanket gas to keep below a certain set point. In addition, to minimize potential of over-pressuring the tank, I was wondering if it's possible to also use a pressure input that would 'override' the oxygen sensor control and limit the control valve opening? In essence, a bit of 'dual' control - is this possible, how is it done (PLC logic?) and does anyone have experience with this type of control system?
Thanks in advance!
Shannon