An operator training simulator (OTS) is a simulator of the plant on which control-room operators train, the way pilots train in a flight simulator before they fly. The operator sits at a copy of the real control-room screens, but the plant behind them is a computer model. A control-room operator is the employee who watches the plant's screens and adjusts the plant, hour after hour.
The reason is simple. In a real plant, the most dangerous events are rare. A compressor may trip once in several years. An operator who has never seen it before may react wrongly. In a simulator, a trainer can create that event as many times as needed, with no risk to people or equipment.
Say a petrochemical plant in Jamnagar trains a new operator on a feed pump failure. The trainer loads a saved scenario and, at a chosen time, makes the feed pump trip in the model. Pressure in the plant starts to rise. The operator must react in the right order within a few minutes. The simulator records every action and the time taken, and the trainer reviews it afterwards.
A plant uses the simulator in two more ways. New operators learn on it before they are allowed in the real control room, which is faster than waiting for rare events. And experienced operators repeat the hardest procedures every year, such as a cold start-up after a long shutdown. Some plants also test a change to the control logic on the simulator before putting it on the plant.
The model behind the screens comes from chemical process simulation, which calculates how flows, pressures and temperatures change. The same model is part of the plant digital twin. Because the twin is kept up to date from the real plant, the simulator can be tested against real behaviour. Plants that practise predictive maintenance also use it to rehearse the start-up that follows a planned shutdown.