(96a) Tuning Averaging Level Control Systems

Level control applications can have two entirely opposite objectives. The most usual objective is to keep the level always at its setpoint, while moving the manipulated variable as much as it takes to steady the level quickly. In contrast, the second objective is how to minimize the movement of the manipulated variable while keeping the level within its alarm limits. The method makes maximum use of the vessel surge capacity in order to stabilize the operation of the process further downstream. Therefore the objective is to tune the controller such that it can handle a flow disturbance without exceeding alarms limits and gradually bring the level back to its setpoint.