An operator training system (OTS) is to a plant operator what a flight simulator is to a pilot. It helps establish expertise and best practices among operators, enhancing process understanding and quality compliance.

Numerous industries use virtual training systems to instruct users in plant operation and equipment handling. In nuclear power plants for instance, training centers have been established to train, qualify and educate personnel. Here, a virtual clone of the control room of a real power plant is created. Similarly pilots are intensively trained on flight simulators that are exact copies of airplane cockpits. Often these training rooms are placed on moving platforms to simulate a realistic flying experience during training. Currently, commercial pilots have several training sessions in a flight simulator before they are allowed to take control of an airplane. Personnel on offshore oil platforms and refineries are also extensively trained not only in handling the control system and process operation, but also in handling process disruptions.

In the chemical industries, optimal operation of production plants is increasingly important, especially when the globalized economy generates enormous pressures on their economic competitiveness. An important factor in being economically competitive is minimizing energy costs in plant operations. In the chemical industries, training systems can play an important role in achieving these targets.

Operator training system (OTS)

An OTS is set up like a real plant and comprises three main components:

The user interface

The user interface is where the trainees interact with the operator training system. Here, all relevant information and process values are presented and the operator interventions can be executed. OTS are differentiated by the type of user interface into two categories:

In a full size OTS the original user interface of the distributed control system (DCS) is used. The operator works on the original operator stations (OS) of the DCS, which has the same look and feel as that in the control room. Normally several OS comprise an operator training system. Sometimes even the complete control room environment is duplicated to reinforce this impression. Alongside the OS is a trainer station (TS), through which the instructor can interact with the operator training system. The instructor loads the actual training scenario and administers the system. In addition to the functionalities that the operator has, the instructor can also initialize special disturbances and scenarios to test the skills of the operator.

A generic system has a reduced operator interface that has the look and feel of an operator station but is not a real operator station. Normally an OTS with a generic interface has only one single user interface and the functions of the trainer station are integrated into this interface. Such training systems are used where the focus is on process training or process demonstration and not on DCS handling. These generic systems can also be used as entry level operator training systems.

The automation system

The automation system controls the process. In an OTS the actual automation system is not used, rather, the configuration of the automation system is loaded into an emulator. All functions that are realized in the automation system are executed in a virtual system. The advantage is that the complete hardware of the automation system is not required. It is also possible to save certain states of the automation environment. These saved states (snapshots) can be reloaded later. This is not possible with the real automation system since it is not designed to start and stop operating but runs continuously once initiated.Sometimes in a generic system, the automation system is not emulated. The functionalities of the automation system are transferred into the process model. Accordingly, the whole range of functionalities is not available but these are not needed in their entirety in such systems.

Numerous industries use virtual training systems to instruct users in plant operation and equipment handling (Photo: Siemens AG)

The process model

The key part of an operator training system is the process model. Here, the behavior of the real plant hardware such as columns, reactors, heat exchangers and pumps are described. The process model is build up from several instances of modeling objects that are interconnected. These objects are described with mathematical equations. A simulator solves these equation systems and calculates the time variation. The modeling of objects can be divided into three main groups:

In rigorous models, component behavior is described using physical, chemical and thermodynamic equations. These relatively complex models accurately describe the real situation. Empirical models are based on expertise. If exact physically, chemically or thermodynamically equations are missing, the behavior can be approximated with phenomenological equations. The simplest models are shortcut models. With just a few simple equations, the principle behavior can be described easily.

Process models are usually a combination of all three model types. Some parts of the plant are described with the shortcut model, others with rigorous models. The more detailed the process model is the better it describes the reality but is consequently more complex. A complex model requires more computation time to be solved by the simulator. Based on the training tasks, at hand, the degree of detail of the process model is defined.

Training scenarios

An operator training system is a virtual plant. With an operator training system, different situations can be practiced. These training situations can be repeated, as often as necessary and the training has no impact on production. Modern plants must be reliable and at the same time aim at maximum onstream time. This means that all operator interactions need to be optimized and the startup time needs to be shortened. In the event of emergencies, safe shutdown procedures have to be executed in exactly the same manner by every operator. These situations do not occur often and consequently operators do not have a chance to become familiar with them.

Additionally, since the introduction of the DCS, the manning of operational crews in the control room has been drastically reduced. Consequently, each operator needs to be familiar with more plant sections and their individual operation procedures. Not only is the safe handling of different plant sections of importance, but also its economic competitiveness. An operator training system ensures that operators are optimally prepared for their jobs. All the various scenarios can be simulated as often as necessary without any impact on the real plant and its production.

Startup

Plant operators can be trained on the startup procedure of a plant as often as required until all operators know what has to be done. Different strategies for startup procedures can be compared and the best one selected. Furthermore, the operators can learn more about the interactions between the different plant sections. This training effect increases process understanding and effectively helps in attaining optimal plant operation.

Emergency situations

Emergency situations can be initiated during training sessions by the trainer. This tests the way in which operators react to exceptional plant operational situations. Should an operator not react in a prescribed manner, the plant disaster occurs only within the simulated environment. The worst that can happen is that the simulation comes to an end with a hint that in reality the disaster has damaged the plant. In the simulator, no real hardware would be destroyed. Thus, the handling of emergency situations can be safely undertaken without risk of any physical damage. By repeatedly practicing these training situations, the operators are well prepared for emergencies. Even if they have no real life experience with emergency situations, they have a good grasp of the situation and are confident that they are well prepared for such situations.

Additionally the operator instructions for such situations can be checked and tested. A detailed review of every step is reasonable and correct can be conducted. This can be carried out before a process upset occurs in the real plant. Consequently, the management is assured that operator procedures and instructions are correct and will work.

Economic operation

Even during normal plant operation an operator training simulator is of great help. Often the production regime has to be changed due to load or product/type changes. This means that the operating conditions of the plant need to be changed. The time required for this switchover should be as short as possible.

With an operator training system, all these operating switchovers can be practiced. By optimizing the type changes, the production of off spec material can be minimized. Even for load changes, an optimized strategy can be developed. The operators can be made conscious of the need to operate the plant at its economic optimum even in partial load situations. For example, they can be trained on how the interaction of reflux and heat duty in a distillation column influences the product qualities. Consequently, the amount of heat demand can be reduced while maintaining the same product quality, thereby optimizing the economic operation of the plant.

Faster plant startup and minimized downtime

Plant staff can be trained in several ways with an operator training system. One result of employing an operator training system is the improved process understanding of all operators and a standardized operational know how amongst them. If the initial startup of a new production plant can be shortened by just a few days or unplanned downtime can be reduced, the investment in an operator training system pays off handsomely.

info:

contact: