Automating Pressure Vessel Process with Schneider Electric EcoStruxure Control Expert (Unity Pro)

By Matthew Loong

Here, I will show a glimpse of how automation can be used to charge and discharge gas into a simulated pressure vessel. You can see a video of the simulation below at our KPMG Operational Technology Lab (see the blue balloon inflating and deflating).

In reality, pressure vessels are robustly constructed containers that can hold a high amount of pressure. They include flash drums, reactors, exchangers, boilers and distillers etc. Design, construction and maintenance standards are stipulated by the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code.

At the inlet of the pressure vessel there is a pump that injects gas into the vessel pressurizing it. At the outlet of the pressure vessel there is a valve that release pressurized gas from the vessel. Of course, this over-simplifies much of the process but the principle remains.

Integrated Development Environment

For this example, I will be using Scheider Electric EcoStruxure Control Expert (formerly Unity Pro). First, we drag and drop the correct PLC modules onto the bus. Then we configure the communication. I will only focus on the ladder logic concepts here.

Ladder Logic

The program is read from top to bottom left to right. Each rung has inputs on the left and outputs on the right.

Explaining each rung:

Rung 1 - This is a seal-in relay. Pushing the start button energizes the run bit on the output and the parallel input switch, latching the circuit.

Rung 2 - The run bit energizes the pump (GP01) turning it on. In parallel, the timer function block is energized and starts timing for 10 seconds. Once 10 seconds is reached, the done output bit (DN1) is energized, breaking the normally closed done input bit (DN1) in parallel. This deenergizes GP01 turning off the pump.

Rung 3 - The energizing of DN1 energizes the valve (GV01). In parallel, the timer function block is energized and starts timing for 10 seconds. Once 10 seconds is reached, the done output bit (DN2) is energized, breaking the normally closed done input bit (DN2) in parallel. This deenergizes GV01 turning off the valve.

Rung 4 - This rung implements a pause of 5 seconds before the cycle repeats itself. The cycle only breaks upon pressing the stop button, energizing the normally closed stop switch on Rung 1.

You can see the animation table in action below.

Naturally, the logic itself is only the tip of the iceberg. You still need to wire up the PLC panel to field equipment and design the HMI for the full monty.

Cybersecurity Aspects

If you are keen to learn more, come join us at our OT Cyber Lab for some hands-on training. There you can launch scripts to modify coils and registers of our industrial grade PLC to attack many other physical processes.