[Back to list of pilot plants & teaching equipment]
Pressure-level process - UML
|
The central part of the device is a closed tank where air - pressure and water - level can be controlled through two pumps.. The air reservoir increases the time constant of the pressure loop and equalises pulses in the air flow. The water flow recirculates in the system and therefore there is no need for any external water input. If any of the process variables exceeds the prescribed operating range the protection device switches off the associated actuator. Normal working conditions of the system can be disturbed by changing set - points of corresponding valves, but there is no possibility of direct measurement of these signals.
Three different types of working conditions can be distinguished: the controlled variable can involve air - pressure only, or water - level only, or both process variables. This of course means that the system can work as a classical single - input single - output system or as multivariable plant due to the fact that in the last case both proces variables are mutually dependent.
[Back to list of pilot plants & teaching equipment]
