Operations hierarchy

Fig. 21 (Bassett et al, 1994). Note that early applications of computer-based on-line optimization worked at the top levels of the process operations hierarchy, where decisions are made less frequently than at lower levels and, consequently, the limited speed, input/output, and storage capacity of early computers were not an impediment. The implicit assumption in this decomposition is that the aggregate of the individually optimal decisions will be close to the overall optimal decision at each point in time. Frequently, this is not the case. Therefore, there exists a strong incentive to establish a framework for the formulation and solution of optimization problems that integrate as many levels as possible above the chemical process level of the Process Operations Hierarchy (Prett and Garcia, 1988 Kantor et al, 1997).

Why is it not trivial to perform an integrated optimization, by merely combining the individual optimization problems at each level of the Process Operations Hierarchy to form a single optimization problem There are a number of reasons ... 

Engineering/Business concepts. Although engineering considerations dominate the lower levels of the Process Operations Hierarchy, business concepts emerge at the higher levels. Therefore, a variety of... 

Fig. 21. Process Operations Hierarchy in the chemical process industries.

Software implementation. The complexity of the integrated optimization problem is exacerbated when implementation issues are considered. A unifying framework is needed that will allow both software and humans involved with various levels of the Process Operations Hierarchy to seamlessly communicate with one another in a decisionmaking process over time. 

Figure 9.4 Initial shooting operation hierarchy levels...

Formulate implementation plans to accomplish prioritized objectives. Implementation and operation Hierarchy of controls... 

Parentheses can be used (and should be used liberally) to reflect the exact hierarchy of operations. The operational hierarchy is the same as for standard algebraic expressions as follows ... 

Lubrication skid. The gas turbine lubrication skid is usually independent of the steam turbine skid as the lubrication oil is usually synthetic due to the high temperatures in the gas turbine. Another reason is due to water contamination of the lubrication oil from the steam turbine. It is advisable to have the lubrication system be totally independent. The gas turbine lubrication skid would report to the gas turbine controller. Since the lubrication system is also used for providing cooling, it is usually operated for about 20 minutes after the gas turbine is shutdown. The lubrication skid contains at least three pumps, two pumps in which each can provide the head required and a third pump, which is usually recommended to be a DC drive for emergency use. These pumps and their control fall under the drive level hierarchy. 

The fuel. skid. This could contain a gas compressor if the fuel gas pressure is low and a knockout drum for any liquid contamination that the gas may have. The requirement of fuel gas pressure is that it should be operated at a minimum of 50-70 psi (3.5-4.83 Bar) above the compressor discharge pressure. The compressor and its motor drive fall under the drive level hierarchy. In the case of liquid fuels, the skid may also contain a fuel treatment plant, which would have centrifuges, electrostatic precipitators, fuel additive pumps, and other equipment. These could be directly controlled by the D-CS system, which would then report its readiness to the gas turbine controller. 

The consequences of these changes were impressive. The parental 434 repressor had no affinity for the P22 operator in vivo, but the redesigned 434 repressor controiled only P22 operators and not 434 operator regions in vivo. Purified redesigned 434 repressor bound specifically to P22 operator DNA in vitro and showed the same hierarchy of affinities for the three regions ORl, 0R2, and OR3 as native P22 repressor. 

Initially, a system s hierarchy is identified for subsystems, sub-subsystems and so on to the components for which data must be found. The top event specifies system failure subsystems required for operation of the system in the mode specified are input to the top event s OR gate. Redundancy is represented by the redundant systems inputting an AND gate. This process of grouping subsystems under OR gates, if they can individually fail a function, or under AND gates if concurrent failures are necessary, is continued to the component or support system level until the tree is completed. This process grades the hierarchy from top to bottom, down the fault tree. 

Establish design review procedures that operate at various levels within the design hierarchy, including subcontractors. 

Figure 11.1 The hierarchy of strategic and operational decisions in preclinical research.

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