Instumentation • Computing • Control
the application and turn off the controller. Te economic impact with APC maintenance is also a significant problem. Te controller downtime, including revamp and turnaround in addition to normal downtime, can reduce total benefit by 35 per cent across a five year cycle. So, for a typical unit, annual benefits of $2.5m (low end) can be achieved, amounting to a loss of $875,000 per APC application.
When this is multiplied across an average of nine major units under APC control per refinery, this totals almost $8 million over the five year period that is potentially lost in benefits from reducing the downtime of the controller. So, 60 per cent of this downtime is spent in revamp, 30 per cent is the underutilisation period of the controller when it is not operating at peak performance and, therefore, not generating maximum benefits and the final 10 per cent is unavoidable where the unit is in turnaround.
Making the difference Today, with Adaptive Process Control engineers can do everything required to update the models without the need to turn off the controller. Tey can also ensure that the controller exhibits robust behaviour during the periods between model updates, make maintenance a built-in and continuous part of the process and eliminate the need to wait for turnarounds to revamp controllers. Crucially, the software permits the engineer to always be in the loop in terms of making decisions when new models would replace existing ones in on-line applications. For more than 20 years, Aspen DMCplus has been the industry standard for advanced process control software. Te application has been successfully applied on large and small units and is the most scalable commercial technology in the industry. Today, with a completely re-designed modelling environment and the introduction of Adaptive Process Control, companies can identify poorly performing aspects of the APC model and pinpoint the areas of the model needing attention. Te additional benefits of are to squeeze out costs
by making improvements to existing solutions and adopting new technologies:
● Reduce controller maintenance labour costs ● Minimise erosion of benefits ● Return controllers to service faster after turnarounds
● Reduce Controller Maintenance Costs by 25 per cent
● Increase benefits by continually improving performance
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● 10 per cent increase in total APC benefits over 4 years
One of the most significant differences with Adaptive Process Control is that companies now have the ability to collect new model identification data using small perturbation background testing as opposed to the aggressive step-testing methods traditionally used. As the new data are collected, they
are monitored in real-time and using AspenTech’s new automated slicing technology bad data are automatically removed producing a clean data set for model identification. Adaptive modelling creates candidate models and those are automatically presented to the engineer for review. Tis entire process is monitored by an automated test agent and the engineer is notified in real-time of any problems that occur within the workflow. Jack Adair, Advanced Process
Control Engineer, Valero Corporation recently commented on Adaptive Process Control: “Te technology works. We achieved the objective of obtaining quality data without unduly disturbing the process or sacrificing economic objectives. Te operators hardly noticed a step test was going on.”
Delivering success APC increases stability and allows the process to operate much more closely to its maximum performance and economic constraints.
Te technology is designed to operate above regulatory controls and adjust the set points of the basic PID loops to achieve better control of the higher level variables. Across the plant, APC technologies improve plant stability by reducing the effects of disturbances on plant. Te plant, therefore, runs more smoothly than with regulatory controls alone. Adaptive Process Control from AspenTech eliminates the need to approach APC maintenance as a project. It creates a continuous process of collecting process data, assessing model quality and generating new models as the behaviour of the plant changes over time. ●
Rob Howard, director of business consulting, AspenTech, Reading, UK.
www.aspentech.com
“Adaptive Process Control eliminates the need to approach APC maintenance as a project. It creates a continuous process of collecting process data, assessing model quality and generating new models as the behaviour of the plant changes over time.”
Rob Howard, director of business consulting, AspenTech.
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