The following Figure illustrates the P&ID of a tank designed for temperature control. The process tank uses a heater to regulate the heating process of the liquid inside it. If the tanks' liquid level is low, i.e., the low-level sensor detected, the inlet flow should be allowed, while the outlet flow should be blocked. When the tank is full, and the high level is detected, both inlet and outlet valves will be fully closed. At this point, the installed heater will be switched on, and the temperature will be continuously monitored using the temperature transmitter.

After the temperature reaches the desired value, the outlet valve will be opened to drain the tank containing the heated liquid, and the heater will be switched off. Two level sensors, namely LLS and HLS, are installed at the bottom and top of the tank to detect low and high levels, respectively. Additionally, a temperature transmitter (TT), such as a thermocouple, is installed to continuously monitor the tank's temperature. Moreover, a heater has been installed inside the tank.

The diagram uses Start, Stop, LLS and HLS as inputs and Inlet Valve, Outlet Valve and Heater as outputs. During the experiment, the temperature readings from the transmitter will be manually entered based on visual inspection.

To start the process, the latching coil and master start-stop buttons are used, as shown in the first rung of the diagram. The second rung controls the Inlet Valve by detecting the LLS. It keeps the Inlet Valve open until the LHS is detected and then latches it. In the third rung, the heater coil energizes when HLS is detected, starting the heating process. This continues until the temperature reaches 50°C. Once the temperature reaches 50°C, the Outlet Valve is opened, and the heater is switched off, stopping the heating process, as shown in the last rung.

The runtime test cases for this experiment are given in the following Table. For instance, as shown in test case 1, if the liquid level in the tank is low, i.e., the LLS detected (or True), the inlet flow should be allowed (True), while the outlet flow should be blocked (False). Similarly, for test case 2, when the tank is full and the HLS is detected (True), both inlet and outlet valves will be fully closed (False). As shown in test case 3, the installed heater will be switched on (True), and the temperature will be continuously monitored using the temperature transmitter (Actual Temperature). Test cases 4 and 5 show that after the temperature reaches the desired value (50°C), the outlet valve will be opened (True) to drain the tank containing the heated liquid, and the heater will be switched off (False).