Design decisions

However, in the early stages of design, decisions that have important safety implications must be made based on an incomplete picture. Let us explore simple quantitative measures which can be used to assist decision making in the early stages of design. 

There is, however, only a limited quantity of by-product power available, and for large process operations the demand for power is usually far greater than the simple steam cycle can produce. Many steam system design decisions fall back to the question of how to raise the ratio of by-product power to process heat. One simple approach is to limit the turbines that are used to extract power to large sizes, where high efficiency can be obtained. 

Catalyst Selection. The choice of catalyst is one of the most important design decisions. Selection is usually based on activity, selectivity, stabiUty, mechanical strength, and cost (31). StabiUty and mechanical strength, which make for steady, long-term performance, are the key characteristics. The basic strategy in process design is to minimize catalyst deactivation, while optimizing pollutant destmction. 

System, Equipment, and Refrigerant Selection There is no universal rule which can be used to decide which system, equipment type, or refrigerant is the most appropriate for a given application. A number of variables influence the finm-design decision ... 

There may be loss of operability and design decision data used to generate the design. 

These measurements with their inherent errors are the bases for numerous fault detection, control, and operating and design decisions. The random and systematic errors corrupt the decisions, amplifying their uncertainty and, in some cases, resulting in substantially wrong decisions. 

Today s high technology products and growing international competition require knowledgeable design decisions based on realistic models that include manufacturability requirements. A suitable and coherent tolerance allocation methodology... 

An important aspect of the simple probabilistic approach used above was that it provided a transparent means of explaining to the company the reasons behind the design decisions. It gave a degree of clarity not provided by a deterministic approach and ultimately gave the engineers more confidence in their designs. 

Making product and process design decisions concurrently instead of sequentially... 

As has been previously discussed in the synthesis of physical MENs, several design decisions are to be made ... 

You should develop a documented procedure for the facility planning activity that will ensure the provision of adequate information on which to base plant design decisions. The procedures should provide for a separate development plan with allocation of responsibilities for the various tasks to be undertaken and should cover the layout, specification, procurement, installation, and commissioning of the new or revised plant. 

The durability of a building (i.e. its life expectancy and its resistance to deterioration) is determined by deliberate design decisions relating to stmcture and choice of materials as much as to the natural or precipitate process of ageing. Within certain limits, the design of an industrial building can and should take into account the predicted use or lifespan of the process or method of operation which it is to accommodate. To aim at durability beyond that has ascertainable cost implications. These may be acceptable if the building is to serve future known or even unpredictable purposes. 

In process design, it is frequently discovered that many of the basic data needed to rmderstand a process are lacking. Because most crrrrent mathematical models are not sufficiently accrrrate to permit direct scale-up of the process from laboratory data to full plant size, a pilot plant must be constracted. As models are improved, it may become possible to evaluate design decisions with more confidence, and bypass the pilot plant stage. 

Equations (24) and (25) are adequate for designing decision trees. The feature that minimizes the information content is selected as a node. This procedure is repeated for every leaf node until adequate classification is obtained. Techniques for preventing overfitting of training data, such as cross validation are then applied. 

If the loss can be measured in money, the cash value of the risk can be compared with the cost of safety equipment or design changes to reduce the risk. In this way, decisions on safety can be made in the same way as other design decisions to give the best return of the money invested. 

No. These methods complement each other. Very often a design decision is made only after analyses with both methods. 

Design for Desired Solids Circulation Rate It is assumed that the total gas flow into the bed is known. When the operating fluidizing velocity is selected for the fluidized bed above the draft tube, the diameter of the vessel is determined. The final design decisions include selection of the draft tube diameter, the distributor plate design, the separation between the draft... 

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