Oct-2006

Managing training simulator projects

Operator training simulators are not cheap, yet their value in preparing personnel for the fast startup and operation of new process plants is significant

Nick Harbud
Foster Wheeler Energy Limited

Article Summary

There is no doubt that over the last 20 years the improvements in the dynamic simulation of process plants have enabled a range of new operational tools to become widely available. Among these is the high-fidelity, customised operator training simulator (OTS), which can now be readily obtained for almost all chemical processes. However, the dazzling advances in OTS technology should not blind us to the fact that these items are a significant expense and their engineering constitutes a major project in its own right.

Typically, an OTS costs in the order of $1 million, which can amount to more than 20% of the combined cost of process control and safety systems. These systems generally take a year to deliver and the OTS must be ready at least six months prior to plant startup. OTS projects require prodigious quantities of input data, including heat and material balances, process flow diagrams, most equipment and instrument data sheets, as well as all the information that would normally be supplied to a distributed control system (DCS) or emergency shutdown (ESD) system vendor, such as piping and instrumentation diagrams (P&IDs), input/output lists, control narratives, and cause and effect diagrams.

If this is not a sufficient challenge, OTS systems are normally understood technically by three groups of people:
• Specialist engineers working for an OTS supplier. This group may comprise no more than a few hundred individuals worldwide
• The process technologist, who comprehends the fundamental chemical engineering that underlies the simulator and who probably developed the steady-state heat and material balance for the real plant
• The plant operators, who can tell whether it provides a realistic simulation of the real plant.

Unfortunately, none of these can normally be spared to manage the OTS project, so it follows that the supervision of an OTS supplier normally falls upon someone who does not have the most comprehensive technical under-standing of what is being ordered. This is often a control systems engineer, as the OTS tends to be perceived as an extension of the DCS.

Generic simulators
Many companies provide so-called generic training simulators for common unit operations, such as boilers, fluidised catalytic cracking, crude distillation and vacuum distillation. These simulators are typically complete packages that run 
on a single computer. The models, instrumentation, screens, DCS/ESD system configurations and training exercises will generally be based upon common industry examples. They cost a few thousand dollars each — significantly less than an equivalent high-fidelity OTS. The generic simulator is an off-the-shelf item that does not require detailed design information from the real plant. It may therefore be procured independently of the main project schedule and delivered to the users many months earlier than a high-fidelity OTS. However, the generic OTS has its drawbacks.

Generic simulators will generally not be available for anything other than commonly used unit operations. Thus, for an application involving, say, a chemicals plant, there is unlikely to be a generic solution available.

The generic OTS will be based upon a typical configuration of a plant and DCS. If the real plant is larger, smaller or of an unusual configuration, its dynamic response may differ significantly from the generic OTS, even to an extent where the training benefit becomes questionable.
Despite the widespread adoption of Microsoft Windows as a platform for DCS operator workstations, the look of the trainee’s interface is unlikely to match that of the real plant DCS. The degree of customisation available on a generic simulator is generally limited.

Overall, any off-the-shelf simulator should be thoroughly investigated before any decision is made with respect to its adoption and, while the generic solution should be considered, one should not rely upon it being either available or entirely suitable.

Two-part OTS architecture
Most modern training simulators use a two-part architecture comprising a mixture of DCS components linked to a dynamic model of the real process plant (Figure 1). Typically, the DCS supplier provides:
• Standard operator consoles to form the trainee workstation
• Computers running DCS controller emulation software, onto which the real plant DCS configuration will be loaded
• An interface server that alternately passes DCS outputs to the plant model and plant model calculated values to the DCS inputs.

The OTS supplier provides:
• A dynamic simulation of the real process plant (the plant model)
• An instructor station for controlling the simulator, running training exercises, initiating malfunctions and evaluating trainee performance.

This is an attractive architecture from the perspective of suppliers, as a single plant model can interface with many types of DCS, and vice versa. From a purchaser’s viewpoint, its main advantage is that the trainees will be learning in an environment that is pretty much identical to the real thing. However, it can have certain limitations, including:
• Limitations on simulator speed and the ability to backtrack or rewind a training exercise
• DCS alarms and events often cannot be recorded within the instructor station or stored as part of the training records
• Storing snapshots, reloading and re-initialising
exercises involving sequences and other complex
control schemes can be problematic.

But whatever the advantages and disadvantages, this is the most likely platform for implementing the OTS. This should be kept in mind when specifying the simulator requirements.