Process simulators aren't just for training

From design to startup and beyond, operator training simulators certainly appear to be worth all the trouble, especially since they can save time and money throughout a process plant's entire lifecycle.

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Some engineers have discovered that working with an OTS is a career-enhancing move, says Randy Wagler, process performance solutions product manager at Honeywell Process Solutions. “The simulator custodian, sometimes a junior engineer, often becomes extremely valuable to the organization, particularly when he or she has participated throughout the OTS’ development period with the simulation vendor,” says Wagler. “This individual becomes familiar with all the major plant systems. For example, the training support person will become familiar with the plant’s design, dynamic behavior of process equipment, control system implementation, and operating procedures. Normally, these disciplines are handled by specialists like process engineers, control engineers, and operations leaders. These skills are rarely found in one individual. Consequently, after the turnover of the OTS, its specialist normally gets reassigned to other higher-level positions where this knowledge can be leveraged during startup.”

Simulating Design
Peter Henderson, process performance solutions product manager at Honeywell Process Solutions, says plant design has changed over the years, and simulation is necessary from the beginning. “Plant design is rapidly evolving from steady-state design to a complete assessment of the plant’s behavior and bottlenecks throughout the entire range of operation with dynamic simulation,” he says. “This proves equipment capacities will provide sufficient performance at alternate operating conditions outside the normal design case. Engineering contractors have recently been doing engineering studies for equipment rating, instrument specification, time constant, valve- stroke times, safety assessment, and control strategy development. Control system vendors are applying control system emulation prior to acceptance testing to eliminate many of the errors that might not be uncovered prior to initial operations during commissioning. The benefit of this is lower commissioning costs and faster plant startups and earlier profits.”

Siemers says using simulation to prove the design of a process is almost always used in new refineries and other oil and gas projects.

“Simulation is far more prevalent and accepted in the refining and oil and gas industries than it is in power generation,” agrees McKim. “Many petrochemical companies maintain staffs of performance engineers that use steady-state design tools in conjunction with or in addition to dynamic simulation to perform sizing/optimizing studies. Dynamic simulation in the power industry is most often used for design studies, of duct implosion, for example, by engineering and procurement contractors (EPCs).”

Jose Maria Ferrer, business consultant for Aspentech, says simulation is often used when proving complex designs. “Wherever you have a compressor network, or a novel design, or a more complex control strategy, dynamic simulators are used about 80% of the time,” he says. “Knowledgeable plant and production managers realize the importance of simulation in the design and implementation phase of their projects, and are leveraging that realism to train their operators on scenarios and procedures to reduce incidents related to operational errors.”

In some cases, dynamic simulation works especially well when vast amounts of historical data are available from similar processes, such as liquid natural gas (LNG) plant design. Honeywell developed an LNG simulator based on operating data from 10 LNG plants to ensure the model was accurate. This helps plant design engineers optimize equipment design, familiarize operators with the plant’s dynamic response, and help prepare them for plant operations.

Having a specific simulator available for a process makes it easier on the engineer responsible. “An important component is the experience and ability of the process engineer preparing the simulation of the process and control models,” says Henderson. “It’s rare to find an individual with the detailed knowledge of the process design, control strategies, and operating philosophies for complex LNG plants.”

When a company wants to build a similar plant, using a simulator on an existing plant can help. For example, Absolut Vodka in Sweden wanted to build another plant, but wanted to make sure its new distillery would produce vodka with exactly the same smell and flavor as the existing plant. The firm used a simulator to investigate how every process variable affects product quality.

Absolut used an HYSYS simulator from Aspentech to build a model of the existing plant, run tests and simulations in the model, and compare the model’s results with data from the real plant. The company’s engineers found that changes predicted by the model occurred in the real plant. Armed with this added assurance, Absolut built its new plant.

Simulators can be used during the design phase to check out HMI displays (See Figure 2), process logic, and software upgrades. Doug Taylor of Concept Systems, a systems integrator in Albany, Oregon, uses simulation techniques to work out what operator interfaces should look like before an automation project starts. “Customers often have a hard time visualizing the optimal operator interface for a new control system, so Concept's engineers ‘mock up’ functional human interfaces using simulation technology,” says Taylor. “Though this simulated interface could be used for operator training, Concept's customers seem to always prefer doing operator training on the actual machinery.”

Mike Lane, another systems integrator, worked with a simulator at a Weyerhaeuser paper mill in Canada, and he agrees with Taylor. “The most significant benefit was the ability to stage and verify graphics,” he reports. “In previous years, there was no way to compile or test graphics. This forced us to conduct all graphics testing and debugging during commissioning, and sometimes during plant startup. The ability to conduct this work offline was judged by the project team to be adequate justification for using Shadow Plant.”

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